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Security Exception in Web.Config On Server [duplicate]

I've encountered an error deploying a site to a server. When trying to load the home page, or access authentication on the new site in IIS, I get the error:
Config Error: This configuration section cannot be used at this path.
This happens when the section is locked at a parent level. Locking is
either by default (overrideModeDefault="Deny"), or set explicitly by a
location tag with overrideMode="Deny" or the legacy
allowOverride="false".
More detail can be found here, in Scenario 7 matches my hex error code.
The solution given on the linked site above is to set Allow for overrideModeDefault in the section mentioned in my error, in the applicationHost.config file. In my case, under Security in system.webServer. But if I look at the applicationHost.config on my local computer, where the site is properly deployed already, that section is set to Deny.
If this solution is correct, how is my local instance running just fine with the same web.config? According to my applicationHost.config, that section should be locked, but it's not. I'd prefer to not change the applicationHost.config file, because there are many other sites running on that server. Is there another solution?

I had the same problem. Don't remember where I found it on the web, but here is what I did:
Click "Start button"
in the search box, enter "Turn windows features on or off"
in the features window, Click: "Internet Information Services"
Click: "World Wide Web Services"
Click: "Application Development Features"
Check (enable) the features. I checked all but CGI.
btw, I'm using Windows 7. Many comments over the years have certified this works all the way up to Windows 10 and Server 2019, as well.

You could also use the IIS Manager to edit those settings.
Care of this Learn IIS article:
Using the Feature Delegation from the root of IIS:
You can then control each of machine-level read/write permissions, which will otherwise give you the overrideMode="Deny" errors.

For Windows Server 2012 and IIS 8, the procedure is similar.
The Web Server (IIS) and Application Server should be installed, and you should also have the optional Web Server (IIS) Support under Application Server.

Browse to “C:\Windows\System32\inetsrv\config” (you will need administrator rights here)
Open applicationHost.config
Note: In IISExpress and Visual Studio 2015 the applicationHost.config is stored in $(solutionDir).vs\config\applicationhost.config
Find the section that showed up in the “config source” part of the error message page. For me this has typically been “modules” or “handlers”
Change the overrideModeDefault attribute to be Allow
So the whole line now looks like:
<section name="modules" allowDefinition="MachineToApplication" overrideModeDefault="Allow" />
After saving the file, the page loaded up fine in my browser.
Warning:
Editing applicationHost.config on 64-bit Windows

You need to unlock handlers. This can be done using following cmd command:
%windir%\system32\inetsrv\appcmd.exe unlock config -section:system.webServer/handlers
Maybe another info for people that are getting this error on IIS 8, in my case was on Microsoft Server 2012 platform. I had spend couple of hours battling with other errors that bubbled up after executing appcmd. In the end I was able to fix it by removing Web Server Role and installing it again.

1. Open "Turn windows features on or off" by: WinKey+ R => "optionalfeatures" => OK
Enable those features under "Application Development Features"
Tested on Win 10 - But probably will work on other windows versions as well.

I ran these two commands from an elevated command prompt:
%windir%/system32/inetsrv/appcmd unlock config /section:anonymousAuthentication
%windir%/system32/inetsrv/appcmd unlock config /section:windowsAuthentication

As per my answer to this similar issue;
Try unlocking the relevant IIS configuration settings at server level, as follows:
Open IIS Manager
Select the server in the Connections pane
Open Configuration Editor in the main pane
In the Sections drop down, select the section to unlock, e.g. system.webServer > defaultPath
Click Unlock Attribute in the right pane
Repeat for any other settings which you need to unlock
Restart IIS (optional) - Select the server in the Conncetions pane, click Restart in the Actions pane

This Did the trick for me, for IIS 8 Windows server 2012 R2
Go to "Turn on Features"
Then go to all default setting , Next, Next, Next etc..
Then, select as shown below,
Then reset IIS (optional) but do it safer side.
This is an additional solution as its a generic problem everyone have different of problem and thus different solution. Cheers!

The best option is to Change Application Settings from the Custom Site Delegation
Open IIS and from the root select Feature Delegation and then select Application Settings and from the right sidebar select Read/Write

On Windows Server 2012 with IIS 8 I have solved this by enabling ASP.NET 4.5 feature:
and then following ken's answer.

To fix this open up the IIS Express applicationhost.config. This file is stored at C:\Users[your user name]\Documents\IISExpress\config\applicationhost.config
Update for VS2015+: config file location is $(solutionDir).vs\config\applicationhost.config
Look for the following lines
<section name="windowsAuthentication" overrideModeDefault="Deny" />
<section name="anonymousAuthentication" overrideModeDefault="Deny" />
<add name="WindowsAuthenticationModule" lockItem="true" />
<add name="AnonymousAuthenticationModule" lockItem="true" />
Change those lines to
<section name="windowsAuthentication" overrideModeDefault="Allow" />
<section name="anonymousAuthentication" overrideModeDefault="Allow" />
<add name="WindowsAuthenticationModule" lockItem="false" />
<add name="AnonymousAuthenticationModule" lockItem="false" />
Save it and refresh Asp.net Page.

In our case on IIS 8 we found the error was produced when attempting to view Authentication" for a site, when:
The server Feature Delegation marked as "Authentication - Windows" = "Read Only"
The site had a web.config that explicitly referenced windows authentication; e.g.,
Marking the site Feature Delegation "Authentication - Windows" = "Read/Write", the error went away. It appears that, with the feature marked "Read Only", the web.config is not allowed to reference it at all even to disable it, as this apparently constitutes a write.

Seems that with IIS Express and VS 2015, there's a copy of the applicationHost.config file at $(solutionDir).vs\config\applicationhost.config so you'll need to make changes there. See this link: http://digitaldrummerj.me/iis-express-windows-authentication/
Make sure these lines are changed per below:
<section name="windowsAuthentication" overrideModeDefault="Allow" />
<section name="anonymousAuthentication" overrideModeDefault="Allow" />
<add name="WindowsAuthenticationModule" lockItem="false" />
<add name="AnonymousAuthenticationModule" lockItem="false" />

In my case it was that on server was not enabled "HTTP Activation" under .NET Framework Features. So for Windows Server 2012 the solution which worked for me was:
Server Manager -> Add roles and features -> Features -> make sure that under .NET Framework of version you want to use is checked "HTTP Activation"

The Powershell way of enabling the features (Windows Server 2012 +) - trim as needed:
Install-WindowsFeature NET-Framework-Core
Install-WindowsFeature Web-Server -IncludeAllSubFeature
Install-WindowsFeature NET-Framework-Features -IncludeAllSubFeature
Install-WindowsFeature NET-Framework-45-ASPNET -IncludeAllSubFeature
Install-WindowsFeature Application-Server -IncludeAllSubFeature
Install-WindowsFeature MSMQ -IncludeAllSubFeature
Install-WindowsFeature WAS -IncludeAllSubFeature

The error says that the configuration section is locked at the parent level.
So it will not be directly 1 config file which will resolve the issue,
we need to go through the hierarchy of the config files to see the inheritance
Check the below link to go through the File hierarchy and inheritance in IIS
https://msdn.microsoft.com/en-us/library/ms178685.aspx
So you need to check for the app config settings in the below order
ApplicationHost.config in C:windows\system32\inetsrv\config. Change the overrideModeDefault attribute to be Allow.
ApplicationName.config or web.config in the applications directory
Web.config in the root directory.
Web.config in the specific website (My issue was found at this place).
Web.config of the root web (server's configuration)
machine.config of the machine (Root's web.config and machine.config can be found at - systemroot\MicrosoftNET\Framework\versionNumber\CONFIG\Machine.config)
Go carefully through all these configs in the order of 1 to 6 and you should find it.

I noticed one answer that was similar, but in my case I used the IIS Configured Editor to find the section I wanted to "unlock".
Then I copied the path and used it in my automation to unlock it prior to changing the sections I wanted to edit.
. "$($env:windir)\system32\inetsrv\appcmd" unlock config -section:system.webServer/security/authentication/windowsAuthentication
. "$($env:windir)\system32\inetsrv\appcmd" unlock config -section:system.webServer/security/authentication/anonymousAuthentication

I needed to change the SSL settings on a subfolder when i got this nice message. In my case following action helped me out.
Opened C:\Windows\System32\inetsrv\config\applicationHost.config
And changed the value from overrideModeDefault="Deny" to "Allow"
<sectionGroup name="system.webServer">
...
<sectionGroup name="security">
<section name="access" overrideModeDefault="Allow" />
</sectionGroup>

In my case, I got this error because I was operating on the wrong configuration file.
I was doing this:
Configuration config = serverManager.GetWebConfiguration(websiteName);
ConfigurationSection serverRuntimeSection = config.GetSection("system.webServer/serverRuntime");
serverRuntimeSection["alternateHostName"] = hostname;
instead of the correct code:
Configuration config = serverManager.GetApplicationHostConfiguration();
ConfigurationSection serverRuntimeSection = configApp.GetSection("system.webServer/serverRuntime", websiteName);
serverRuntimeSection["alternateHostName"] = hostname;
in other words, I was trying to operate on the website's web.config instead of the global file C:\Windows\System32\inetsrv\config\applicationHost.config, which has a section (or can have a section) for the website. The setting I was trying to change exists only in the applicationHost.config file.

In my case, it was something else.
When I loaded the solution in a new version of Visual Studio, VS apparently created a new project-specific applicationhost.config file:
MySolutionDir\.vs\config\applicationhost.config
It started using the settings from the new config, instead of my already customized global IIS Express settings.
(\Users\%USER%\Documents\IISExpress\config\applicationhost.config)
In my case this was the setting that needed to be set. Of course it could be something else for you:
<section name="ipSecurity" overrideModeDefault="Allow" />

Received this same issue after installing IIS 7 on Vista Home Premium. To correct error I changed the following values located in the applicationHost.config file located in Windows\system32\inetsrv.
Change all of the following values located in section -->
<div mce_keep="true"><section name="handlers" overrideModeDefault="Deny" /> change this value from "Deny" to "Allow"</div>
<div mce_keep="true"><section name="modules" allowDefinition="MachineToApplication" overrideModeDefault="Deny" /> change this value from "Deny" to "Allow"</div>

Can You try this:
Go to application path where you're getting deny error, right click
Properties->Security tab
In that, change the permissions and check the checkbox read and write. Then it will work without any error hopefully.

For Windows Server 2008 and IIS 7, the procedure is similar.
please refer to this:
http://msdn.microsoft.com/en-us/library/vstudio/bb763178(v=vs.100).aspx
in add role service, u will see "Application Development Features"
Check (enable) the features. I checked all.

In my case I was getting this error when attempting to update the authentication settings in IIS also in addition to browsing. I was able to remove this error by removing the authentication setting from the web.config itself. Removing a problematic configuration section may be less invasive and preferable in some cases than changing the server roles and features too much:
Section Removed:
<security>
<authentication>
<windowsAuthentication enabled="true" />
</authentication>
</security>

I had the similar issue, but I used the following powershell script which helped me to achieve above steps in on button click.
#Install IIS
Import-Module ServerManager
Add-WindowsFeature Web-Server, Web-Asp-Net45, Web-Mgmt-Console, Web-Scripting-Tools, NET-WCF-HTTP-Activation45, Web-Windows-Auth
the list of features can be added or removed based on the requirement.

I had an issue where I was putting in the override = "Allow" values (mentioned here already)......but on a x64 bit system.......my 32 notepad++ was phantom saving them. Switching to Notepad (which is a 64bit application on a x64 bit O/S) allowed me to save the settings.
See :
http://dpotter.net/technical/2009/11/editing-applicationhostconfig-on-64-bit-windows/
The relevant text:
One of the problems I’m running down required that I view and possibly edit applicationHost.config. This file is located at %SystemRoot%\System32\inetsrv\config. Seems simple enough. I was able to find it from the command line easily, but when I went to load it in my favorite editor (Notepad++) I got a file not found error. Turns out that the System32 folder is redirected for 32-bit applications to SysWOW64. There appears to be no way to view the System32 folder using a 32-bit app. Go figure.
Fortunately, 64-bit versions of Windows ship with a 64-bit version of Notepad. As much as I dislike it, at least it works.

I had the same issue.
Resolved it by enabling Application Server feature. Restarted iis
after that.

This worked for me
Also in IIS 8 you can solve this problem by changing the server to IIS Express. Goto debug->Properties
In the Web select the server as IIS Express from the dropdown and then rebuild the solution

To make a change at Application Level (Web.Config):
Please remove the Trust Level from the web.config:
Actually I was getting this error when I was trying to host my Website on the Hosting Server where I don't have control on their Server. Removing the above line from my Application web.config solved my issue.

Unable to access temporary asp.net files

I'm running Win 10, VS Express for Web 2015. I have an existing asp.net membership database that I want to amend using the Web Site Administration Tool.
I followed this hack to manually start the Web Site Administration Tool via the IIS: Visual Studio 2013 and ASP.NET Web Configuration Tool
The Web Site Administration Tool launches fine. However, when I go to the security tab, I get the following error message: Access to the path 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\19aec8c6\ee1f4195\hash' is denied.
I've gone into the Temporary ASP.Net files folder and changed the properties for my userid to give me full control, yet I continue to run up against the same error.
Update: I turned on the IIS in the Windows Feature and that seemed to make some progress. Now when I run the Web Site Administration Tool, I get a different error when I click on the security tab: Access to the path 'C:\Users\XXXX\AppData\Local\Temp\Temporary ASP.NET Files\root\19aec8c6\ee1f4195\hash' is denied.
Any suggestions?

Did you notice the update left on the referenced answer;
IMPORTANT EDIT: I am sorry, I just realized that it matters if you start console with administrator priviledges. Don't do that. If console has administrator rights, the Web Configuration Tool shows this error on the Security page:
There is a problem with your selected data store. This can be caused by an invalid server name or credentials, or by insufficient permission. It can also be caused by the role manager feature not being enabled. Click the button below to be redirected to a page where you can choose a new data store. The following message may help in diagnosing the problem: Access to the path 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\1c3fef5c\2180c7f9\hash' is denied.
Looks like the same issue.

Just Change TEMP location to "C:\Windows\Temp" and restart Visual Studio
If you wish, you can reset TEMP location to "%USERPROFILE%\AppData\Local\Temp" after work fine.

CS0016: Could not write to output file - 'The directory name is invalid. ' [duplicate]

In Brief
When I attempt to browse my website, I get the following error message:
CS0016: Could not write to output file 'c:\Windows\Microsoft.NET\Framework64\v2.0.50727\Temporary ASP.NET Files\www\xxx\yyy\zzz\a.b.dll' - 'The directory name is invalid'
In Detail
I have two web-sites on my Development PC (fictitious names):
Web2 - this is written in ASP.NET using .NET 3.5 and runs in an AppPool that addresses the v2.0 .NET framework and runs in an Integrated mode. This is developed using Visual Studio 2010
Web4 - this is written in ASP.NET using .NET 4.5 and runs in an AppPool that addresses the v4.0 .NET framework and runs in an Integrated mode. This is developed using Visual Studio 2012.
Recently, I've been working in VS2012 on Web4 almost constantly and it works fine, however the other day I tried to run Web2 and got the exception displayed above.
Bizarrely, part of the path (which I replaced above with letters "zzz") appear to point to a German language path, since it's "\de-DE\" - I'm not operating in German, so I've no idea where it got this idea from.
One thing that is almost certainly un-related, but for some unknown reason I feel it's important to mention: I was using the Performance Analysis tool in Visual Studio 2012 the day before this problem first appeared and I don't know if this might have made some changes to my computer...??
Attempted fixes
There are quite a few threads regarding this on the internet; some threads end in success where file access permissions have been altered whilst others finish on a somewhat desperate sounding note... I have gone through the process of comparing the NTFS permissions on all relevant sounding directories on my PC with that of a colleagues on whose machine this is still working. Unfortunately, no joy to be had there.
I have also un-installed asp.net 2.0 and re-installed it using:
C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_regiis.exe -u
C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_regiis.exe -ir
and again, no joy to be had there either.
My Web4 continues to run unaffected.
Also FYI: using IIS 7.5 on Win7 x64.
I'm now turning to the this wider audience in the hope of turning my current state of despair into one of success.
Thanks everyone
Griff

In IIS Manager, in the advanced settings of the Application Pool, make sure "Process Model > Load User Profile" is set to "True".
I had this exact same problem. I tried changing permissions, disabling anti-virus, creating a new app pool, and reinstalling .NET. I even created a new site with just a "Default.aspx" page and tried to view that site. Even that site had the compilation error. Finally, I noticed that my app pools (clean test site and main site) had the non-default value "False" for the Load User Profile setting. I set that back to true and the issue went away.

The answer was found using ProcMon:
http://technet.microsoft.com/en-us/sysinternals/bb896645
The temporary asp.net files are first created in the user's temp folder and then moved into this folder. For some as yet unknown reason, the compilation for my Web2 site (.NET 2 AppPool) now uses the same folders as my Web4 (.NET 4 AppPool) site.
I used ProcMon to identify all results for "access denied" and gave the IIS_IUSRS group write permissions (and in one case - C:\Users\ASP.NET V4.0 Integrated - modify permissions).
I have no idea why the compilation is using the "wrong" folders and I suspect I may have over-elevated the permissions in some cases, but for now it's working.

In case the above answers didn't fix it for you, check your environment variables (right-click on Computer -> Properties -> Advanced System Settings -> Advanced tab -> Environment Variables
Make sure the temp variables are pointing to a folder with all the necessary permissions. (full access for Network Service, IIS_IUSRS)
Note: don't check just the two variables at the top, look inside the scroll menu under System Variables. You might find the variables configured there too.

It may not be the cause, but this error started occurring for me after trying to run VS 2010 Performance Wizard with the Instrumentation method.
A quick fix in my DEV environment: changed the Identity of the Application Pool of the app to LocalSystem.

Error - Unable to access the IIS metabase

After installing Visual Studio 2012 and opening my solution I get a series of errors in this form:
The Web Application Project Foo is configured to use IIS.
Unable to access the IIS Metabase. You do not have sufficient privilege to access IIS web sites on your machine.
I get this for each of our web applications.
Things I have tried:
Running Visual Studio as Administrator
Running aspnet_regiis.exe -ga MyUserName
Running aspnet_regiis.exe -i
These seem to be common solutions for this problem but I have not had any success with them.
Is there anything else I can try to do?

On Windows 8 Pro:
%systemroot%\inetsrv\config
On Windows 7 and 8.1 and 10
%systemroot%\System32\inetsrv\config
(Where %systemroot% is usually C:\Windows)
Navigate to the appropriate location above in Windows Explorer. You will be blocked access with a popup which says:
"You don't have access to this folder - Click continue to permanently get access to this folder"
Click 'continue' for this folder, and with the Export folder underneath. I changed the shortcut back to "Run as me" (a member of the domain and local administrators ) and was able to open and deploy the solution.

I think you are not running visual studio with administrator permissions. Look that:
http://bloggingabout.net/blogs/rick/archive/2012/10/04/unable-to-access-the-iis-metabase.aspx
To quote
The solution to this is simple: start your Visual Studio with "Run as
Administrator". You can do this by right clicking the shortcut and
selecting "Run as Administrator".

I think we encountered a similar problem at work. For us, the solution was to go into Control Panel -> Programs and Features -> Turn Windows Features on or off... inside that, we had to select Internet Information Services -> Web Management Tools -> IIS 6 Management Compatibility -> IIS Metabase and IIS 6 configuration compatibility.
Give that a try and let me know if it helps!
Note: We're running IIS 7.5 on Windows 7 using both Visual Studio 2005 and 2010 and doing stuff with super-old-school WebServices (.asmx)...

I resolved this issue by granting IIS AppPool identity permissions to the %systemroot%\inetsrv\config

If you are working on a project which does not require the use of IIS, then a workaround to open the project with this error is to simply right click on the unloaded project and click edit, search for:
<ProjectExtensions>
<VisualStudio>
<FlavorProperties GUID="">
<WebProjectProperties>
<UseIIS>True</UseIIS>
</WebProjectProperties>
</FlavorProperties>
</VisualStudio>
</ProjectExtensions>
</Project>
and set USEIIS to false
<UseIIS>False</UseIIS>
reload the project by right clicking on it after saving changes.

I have had two seperate types of problem lead to this error, and thought I'd share...
1. The directory was on an network share and due to UAC restrictions, was
unable to be accessed -- even when running as an admin.
2. The directory was on a drive that didn't exist...
Both of these stem from an unfortunate (imo) choice by MS to put things in the Documents or My Document directory, combinee with really lousy error messages. In both of the above cases the fundamental problem was that the IISExpress Config file goes in My Documents, and it either didn't exist or couldn't be accessed.

Thank you to everyone that answered. Since this was closed for a long time I couldn't provide much feedback, but I did eventually fix my problem. I tried many of these other solutions and they didn't fix my issue, but I'm sure they help when the root cause is different.
My Solution
I solved this problem by turning off the IIS and .Net Framework features within Windows 7 and then turning them back on. It seems like this re-installation is what fixed my issue. I still don't know what caused the problem, but at least one other developer on my team had the same issue.

Navigating to folder: %systemroot%\System32\inetsrv\config presents a security dialog. Click continue and this may resolve the issue. This has worked on two separate Win 10/VS 2017/IIS machines.

On a windows 81, from an admin command prompt, use:
icacls "C:\Windows\System32\inetsrv\config" /t /grant "IIS AppPool\DefaultAppPool":(R)
Then go back in VS, right click on the failed project, choose Reload.
Credit to: IIS7 Permissions Overview - ApplicationPoolIdentity

I had this problem - the symptoms were the same, but the issue I had was that I had set the "My Documents" folder to be on a network share, and the share was not accessible.
The root problem was that the IIS config files located at %USERPROFILE%\Documents are not accessible. Once I changed the "My Documents" folder location (I modified the reg value), it started working again.
I know that this may not be a common scenario that you might run into, but I've posted it here because it gives the same symptoms.

I came across this today and fixed the problem by removing the IISUrl from the Project file:
Right click project
Click Edit
Delete the following line:
<IISUrl>http://localhost:xxxxx </IISUrl>
Reload project
Now add a new IIS virtual directory by right clicking Project > Properties > Web and selecting Use Local IIS Web Server (Uncheck Use IIS Express) and clicking the Create Virtual Directory button.

You might run across this problem and have same problem as me. I "solved" it before and then power outage and computer crashed, not sure why a registry setting reverted but it is the SOURCE of my problem.
I tried all the running as adminstrator
All the IIS / IIS express re-installs.
Various "hacks"
Came down to having to fix the registry again.
Could not as administrator even open regedit (Need to access registry since problem is not with gpedit.msc admin template )
UnHookExec.inf on desktop
Just save UnHookExec.inf and install it by right clicking and selecting install. Installing the file will not show any popup or notice box.
http://www.tweakandtrick.com/2011/04/enable-regedit-registry-editor.html
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\Personal pointing to non-existant fileshare. Changing that to local path solved this problem for me. – Pasi Savolainen Jul 14 '14 at 8:41
(changed from \\cs2data\home\stickelt\my documents to c:\dev )
Now ALL is good and Visual Studio opened solution with 15 projects and connects to IIS and does not complain about not being able to access iis metadata
I had never ran into this before, as nobody at current job had this problem ( many have been here a long time, some got clones of other machines that "worked" and many are on another domain etc.. )

I just had this issue today and I found that I didn't open VS as 'Run as Administrator'.
After doing this, I was able to publish the Service.

If you have administrator permissions, Right Click to Visual Studio icon > properties and then advanced, "Run as administrator" check.
You can run visaul studio as administrator directly anymore.
This way, formal and so basic.

In addition to the answer by #nologo, I also had to use IIS. So I changed the
<UseIIS>True</UseIIS>
to 'False' first.
Opened the solution and ensured that the project could be loaded.
Close solution and that instance of Visual Studio
Change the value to 'True' again
Open the solution.
This time, I didn't get any error/warning. I could also run with Ctrl+F5 or F5 without any problem while my project was mapped to an IIS website.

Changing this key worked for me:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\Personal
The location didn't exist.

Go to the root directory of your project and find the following file:
YourProjectName.csproj.user - inside it, make sure UseIISExpress is set to false:
<UseIISExpress>false</UseIISExpress>
If that alone doesn't work try the following as well and try again:
YourProjectName.csproj - inside the main project file, make sure both UseIIS and UseIISExpress are set to false:
<UseIIS>True</UseIIS>
<UseIISExpress>false</UseIISExpress>
After changing these I was able to load the project again.
Note: Make sure you run your VS as an Administrator, as mentioned in the other answers.

I also had a similar problem. My solution is an extension to the answer "Run as admin" which I hope someone might find useful.
I was running VS2012 and almost every time I had to do the Right Click, Run As Administrator. I got tired of this so instead I went into its properties on the shortcut, clicked advanced, and then clicked the "Run as Administrator" option. Now VS2012 always runs as administrator whenever I open it from that shortcut.
The from that shortcut bit is important. I proceeded to branch my project, and download the branch to a new local folder. Then, when I opened it from the shortcut I had no problem. But if I went directly into the folder, and ran the project locally without the shortcut, it did not run as administrator and I got this error.
Once I opened VS2012 as usual first, then using File/Open/Project It worked again no problem. (because I was running as admin). But I wasn't running as admin when I opened the solution using windows file manager.
The other suggestions seem somewhat extreme, but this is pretty simple so I would tend to give this a try first.
Hope this was helpful.

This seems like one of those "All errors lead to this message" type of bugs.
Mine was that the App Pool was just turned off. I turned it back on, and everything worked fine.

One more thing you could try:
Check if you have pending Windows updates.
If you do, please reboot before trying anything else.
I tend to never shut down my machine, so I had plenty of them waiting for a reboot. And that fixed it.

I tried everything above. The credit goes to all of the responses above. Having tried all of the suggestions on their own, I just assembled this combination of suggestions in an order that made sense to me. Note my Documents folder is on a shared drive. The subst/IISExpress stuff is not applicable unless you're in the same boat.
Configure VS to run as admin
Uninstall IIS via Add/Remove Programs, Windows Features
Reboot
Run WinRAR or something similar as admin and archive C:\windows\system32\inetsrv\
Run cmd as admin and rmdir /s c:\windows\system32\inetsrv\ to completely remove all traces of the last install. Leave elevated cmd prompt open for later.
Reinstall IIS with IIS 6 Metabase compatibility (doubt this was necessary)
Leave Default AppPool and Default Website as-is (I had previously deleted both)
Ran C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -ga MYDOMAIN\scottt732
Ran C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i
Also, because my Documents folder is on a share drive, I was having IIS Express issues. I don't use/like IIS Express, but Visual Studio complained about it.
From elevated cmd prompt, ran subst U: c:\Temp. Created C:\Temp\Documents\ and copied the IISExpress folder from my U drive.
Created CustomUserHome key in HKCU\Software\Microsoft\IISExpress with C:\Temp\Documents\IISExpress
This allowed me to get Visual Studio to open my web projects and edit the properties. I tweaked the projects to store web server settings in a user file and adjusted it to use a Custom URL (not sure if this was necessary)
I may/may not have to run the subst command each time I restart. Don't care.
And after throwing in the towel 3 times and spending roughly ~6 hours I can open web projects in Visual Studio (2015 Update 2).

I just had the same issue with me today. And I found it annoying. Though I have other two websites already under development from the same IIS but still was not able to create new site. Strange, but I did this.
Delete the site from IIS
Create new site, give it a name "new_site"
Select Application Pool other than the site name itself. So it wont be messing up with default settings.
Keep IP "unassigned" if you are running it from same machine
give it some unused port
Run Visual Studio as "Run as Administrator" by right-clicking on VS executable shortcut.
You are done!
You do not need to turn off/re-install anything other than what I have stated since it works.
Let me know if anybody had the same issue just like me and solved the same way. I think it was not the issue but a wrong way of creating website on localhost which Visual Studio rejects to open.
I hope this will help newbies.

Create a shortcut to the "devenv.exe"
select the "Run as administrator" option for the shortcut
doble click on the short cut and reopen your project

I had the same problem after Adding feature from this link afterward I followed this article the issue was gone.

I did a repair of Visual Studio 2015 to solve this.
The repair took a long time, but it solved the issue while doing much of the above did not. I am running Win 7 enterprise.

Open visual studio command prompt and type below command and run
aspnet_regiis -ga machinename\ASPNET
After running the above command Reset the IIS and test the application that resolve your issue.
If above command doesn’t resolve your problem then try to run below command in visual studio command prompt:-
aspnet_regiis -i
Alternatively we can run above command from our windows command prompt also
Go to the Start menu and open Run and enter and click OK
%windir%\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe –I
After that Reset the IIS and test the application that resolves your issue

In Visual Studio 2015:
I changed UseIIS in .csproj file to false and it worked for me.
<UseIIS>False</UseIIS>

In my message, beside complaining about "Unable to access the IIS metabase", it also mentions can't access "<IISUrl>http://localhost:6416/</IISUrl>". Right click on the unload project, click Edit, find the line "<IISUrl>http://localhost:6416/</IISUrl>", comment it out. Reload and it should work. This has to do with administrator doesn't have permission to access that address.

I had a similar problem. Visual Studio would not load any web projects and showed the error: creation of virtual directory <myproj:myport> failed. Unable to access the IIS metabase.
In my case it was actually IISExpress that was at the root of the problem. Right clicking on IIS Express in Programs and Features in the control panel and choosing repair fixed the issue in less than two minutes.

I'm using Win 8 Pro and VS 2013.
After trying everything in this page... I simply reinstalled IIS Express 8 and everything works fine now (even without running as an admin).
My conclusion is that this is a rather generic error and there are multiple root causes.

The Web Application Project [...] is configured to use IIS. The Web server [...] could not be found.

I have a web project in my solution file that is "unavailable" when I open the solution. When I right-click on the web project and reload the project, I get the following error:
The Web Application Project mycompany.myapp.mywebproject is configured to use IIS. The Web Server 'http://localhost/MyWebApp could not be found.
I have not manually set up virtual directories for this web application.
Per colleagues, Visual Studio should prompt me to create virtual directories but I am not getting prompted.
I installed VS2010 before installing IIS on my dev machine.
Here is my development machine setup:
Windows 7 Enterprise
Service Pack 1
64 bit OS
Visual Studio 2010 Enterprise Service pack 1
IIS version 7.5

Since the accepted answer requires IIS Manager, and IIS Express doesn't have IIS Manager or any UI, here's the solution for you IIS Express users (and should work for everyone else too):
When you open Visual Studio and get the error message, right-click the project Solution Explorer and choose "Edit {ProjectName}.csproj"
In the project file, change the following line:
<UseIIS>True</UseIIS>
to
<UseIIS>False</UseIIS>
Save the file.
Now reload your project.
Done.
You'll then be able to open your project. If at this point, you want to use IIS, simply go to your project properties, click the "Web" tab, and select the option to use IIS. There's the button there to "Create Virtual Directory". It may tell you that you need to run Visual Studio as an administrator to create that directory, so do that if needed.

Open the project folder and delete {Project}.csproj.user, then reload the project on Visual Studio.

When this happens the easiest solution is to make the virtual directory manually.
First of all, you need to make sure you have the right version of ASP.Net installed and that you have installed the IIS extensions.
To do this, go to the relevant .net version's folder in C:\(Windows)\Microsoft.NET\Framework\(dotnetver)\
(substituting the bracketed folders for the right folders on your PC) and run this command
aspnet_regiis.exe -i
Next once that's run and finished, sometimes running
iisreset
from the command line helps, sometimes you don't need to.
Next, go to your IIS Manager and find you localhost website and choose add a folder.
Browse to the folder in your project that contains the actual ASP.Net project and add that.
Finally, right click on the folder you added and you should have an option that says 'convert to application' or 'create virtual directory' or something similar.
!!Make sure the Virtual directory has the name 'MyWebApp'!!
Reload your solution and it should work.
Please be wary; this isn't a programming question (and shouldn't really be posted here) but I've posted this guidance as it's a common problem, but the advice I've posted is generic; the commands I've listed are correct but the steps you need to do in IIS may vary, it depends on your version and your account privileges.
Good luck!

This solution worked for me: Right click the Project and select edit and find the following code as shown below in the picture.
change the <UseIIS>True</UseIIS> to <UseIIS>False</UseIIS>
OR
change the <IISUrl>http://example.com/</IISUrl> to <IISUrl>http://localhost/</IISUrl>

For my project, I had to delete these two lines from .csproj file
<ProjectGuid>{3AA499DF-4A65-43B7-8965-D08A4C811834}</ProjectGuid>
<ProjectTypeGuids>{349c5851-65df-11da-9384-00065b846f21};{fae04ec0-301f-11d3-bf4b-00c04f79efbc}</ProjectTypeGuids>
I tried deleting only the first one, but it wasn't enough.
EDIT: As many users have pointed out, this can change your project type or mess with your source control program. I can't investigate these issues as it was a school project I do not have anymore.
Please be careful when trying this. At least make a copy of what you delete.

Edit the .csproj or vbproj file. Find and replace these entries
<UseIIS>true</UseIIS> by <UseIIS>false</UseIIS>
<UseIISExpress>true</UseIISExpress> by <UseIISExpress>false</UseIISExpress>

In my case, this problem was caused by broken IIS bindings. Specifically, my 'http' binding had been deleted. Recreating it fixed the problem.

Cause: The IISURL inside project.csproj is not correctly reflected in the project setting, and the virtual directory was not created.
Solution: Change the Project URL to correct PORT and create the Virtual Directory to make the missing PORT available.
Follow Below Steps:
Step 1: Right click on the project file to Edit the project.csproj file.
Step 2: Search IIS and modify from <UseIIS>True</UseIIS> to <UseIIS>False</UseIIS>
Step 3: Right Click Project to Reload the Project. After Reload successfully, right click Project and select Properties.
Step 4: Locate Project URL option under Properties => Web
Step 5: Change the Project URL to IIS URL indicated both on the Error Message and on the <IISURL>http://localhost:8086 </IISURL> from project.csproj file. Then Click Create Virtual Directory. Save All
Step 6: Redo Step 2 so it doesn't impact the remote codebase and the server deployment settings.

This worked for me:-
Make all your IIS websites point to localhost(All Unassigned) only

Try opening Visual Studio with Administrator privileges. In my case, it gave access to the IIS site and made this error go away. I was then able to switch the project to use IIS Express which doesn't seem to need administrator privileges.

If you are connected via TFS, open your project.csproj.user file and check for
<UseIISExpress>false</UseIISExpress>
and change it to true.
<UseIISExpress>true</UseIISExpress>

You will not believe that, start visual studio as Administrator
as obvious from the message
The Web Server 'http://localhost/MyWebApp' could not be found.
could not be found because may it has no privileges to see it
so Just restart visual studio as Administrator

You can load the project without setting the value of attribute UseIIS to true.
Simply follow the below steps:
In the mywebproject.csproj file--
Delete the tag < IISUrl>http://localhost/MyWebApp/< /IISUrl> and save the file.
The application will automatically assign the default port to it.

In my case I wanted to switch from http to https, so I had deleted http from IIS. In my .csproj.user file found that I still had:
<IISUrl>http://localhost/</IISUrl>
So I changed it to:
<IISUrl>https://localhost/</IISUrl>

In my case I was able to open the solution in offline mode just running the command:
iisreset

For you Win8 users out there, if you follow the steps in the accepted answer, console spits out a message at you saying "thou shalt not use the command-line to execute this command" (paraphrasing). Instead, access the Programs & Features via Control Panel (or Windows + R > appwiz.cpl), click 'Turn Windows features on or off', and make sure you have the following installed:
Internet Information Services
> World Wide Web Services
> Application Development Features
> ASP.NET 4.5
This will check a bunch of other options as well. As soon as I installed these features, and ran VS2012 with elevated permissions, I was able to launch my app successfully.

This happens with me when I tried to open a project from the .csproj file, but I get over it by opening the project from VS:
File> Open> Web Site
and select the directory which include my project.

I had this error, too. I thought everything was setup correctly, but I found out that one thing was missing: The host name I used for my project was not (yet) resolvable.
Since my app determines the current client's name from the host name I used a host name like clientname.mysuperapp.local for development. When I added the development host name to my hosts file, the project was loadable again. Obviously, I had to this anyway, but I haven't thought that VS checks the host name before loading the project.

Check if IIS Express is installed. If IIS Express is missing, Visual Studio might discard the setting <UseIISExpress>false</UseIISExpress> and still look for the express.

in my case, make sure you have a "Default" website

In my case, the "Default Web Site" in IIS didn't have a binding for localhost on port 80.
You should have a binding for whatever your value in the .csproj file is.

I fixed this simply by reinstalling IIS Express after downloading from below link:
https://www.microsoft.com/en-us/download/confirmation.aspx?id=48264

Turns out my IIS was working on localhost:8181.Had to configure the {Project}.csproj file.
<ProjectExtensions>
<VisualStudio>
<FlavorProperties GUID="{349c5851-65df-11da-9384-00065b846f21}">
<WebProjectProperties>
<UseIIS>True</UseIIS>
<AutoAssignPort>True</AutoAssignPort>
<DevelopmentServerPort>7386</DevelopmentServerPort>
<DevelopmentServerVPath>/</DevelopmentServerVPath>
<IISUrl>**http://localhost:8181/ProjectName**</IISUrl>
<NTLMAuthentication>False</NTLMAuthentication>
<UseCustomServer>False</UseCustomServer>
<CustomServerUrl>
</CustomServerUrl>
<SaveServerSettingsInUserFile>False</SaveServerSettingsInUserFile><EnableWcfTestClientForSVCDefaultValue>True</EnableWcfTestClientForSVCDefaultValue>
</WebProjectProperties>
</FlavorProperties>
</VisualStudio>
</ProjectExtensions>

In my case, the url referenced in the csproj file was incorrect.
It needed to be prefixed with www.
I made the changes, saved the file and the project loaded fine.

I ran into this issue when the <ProjectTypeGuids> element in the .csproj file contained the unit test project GUID: {3AC096D0-A1C2-E12C-1390-A8335801FDAB}.
Removing it made the project load without problems.

For DNN users my issue was I needed a binding for dnndev.me at port 80. I have multiple installs that run on different ports and VS requires that that particular Url to exist on port 80 (not 86 like mine was).

Follow this completed solution step by step. it's works for me in VS 2017.
Open Command prompt in administrator mode
Open File explorer and got to .NET Framework folder
Eg:C:\Windows\Microsoft.NET\Framework\v4.0.30319
v4.0.30319 this is my .NET folder. you want to select your relevant folder.
in CMD - Go to .NET folder path
cd C:\Windows\Microsoft.NET\Framework\v4.0.30319
Execute below command in CMD
aspnet_regiis.exe -i
You can see this message finally - Finished installing ASP.NET (4.0.30319.0)
iisreset
You can see this message finally - Internet services successfully restarted
Open IIS in your computer (if not config Follow this)
Go to Site and right click
Add WebSite
Fill - Site name and select physical path
Then type port number (you can find port number in .csproj file and port number must equal with (IISUrl)
EG : <IISUrl>http://localhost:15724/</IISUrl> my port is 15724
Note : you cannot create port 80 number. because it used default IIS page
Click Ok
Open visual studio with administrator permission
Then right click and reload your project
Your Problem may be solved.

This may help some people in 2020. The main issue is that the IIS settings in the CSPROJ file don't match with the configuration for the machine. For example, if you had the Web Application Project pointing to localhost:12345, and a virtual directory isn't set up on the machine on that port, you'll get this error.
Using VS2019, I had this same issue, and the IIS settings in the CSProj file were being ignored. The reason for this is a new property in the CSProj file called "SaveServerSettingsInUserFile":
<ProjectExtensions>
<VisualStudio>
<FlavorProperties GUID="{349c5851-65df-11da-9384-00065b846f21}">
<WebProjectProperties>
<SaveServerSettingsInUserFile>True</SaveServerSettingsInUserFile>
</WebProjectProperties>
</FlavorProperties>
<UserProperties UseAjaxifiedTemplates="True" UseJQuerySupport="True" />
</VisualStudio>
</ProjectExtensions>
When this is set to TRUE, the IIS/Web server properties are in the
.CSPROJ.User file of the same project name.
This allows individual users of a project to have their own IIS settings, provided this file is not checked into source control.
You can control where the settings are stored using Visual Studio GUI in the properties for the project under "Web", "Apply server settings to all users"
When this is on, the IIS settings are stored in CSPROJ, when off, they are stored in CSPROJ.User