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C# Couldn't process file xxx.resx due to its being in the Internet or Restricted zone or having the mark of the web on the file

I have an issue while I try to build project in VS2012.
It cannot build due to the error:
Couldn't process file xxx.resx due to its being in the Internet or Restricted
zone or having the mark of the web on the file. Remove the mark of the web if
you want to process these files.
Here is a similar question.
but I tried that option and had no luck, because I did not download the file from the internet. That project was built from scratch. In project after selecting Properties, in Windows Explorer nothing happened. I do not have the "unblock" option, only the default three options (read only, hidden, and archived).
I have the same error and cannot build or rebuild the project. I have a theory that it is a recent error after updating Windows. Before the update, everything worked fine. Any ideas?

Go to xxx.resx file in Windows File Explorer. Right-click and select properties. At the bottom of the the dialog is an "unblock" option:
Check this and click Apply. Clean your solution and it will build.

In my case I had the same problem with many files.
My solution with VS Prof. 2017 V15.95 was:
Open powershell and execute dir -Path [directory path] -Recurse | Unblock-File
Rebuild all

On the solution folders locate abc.resx.
Open the file using any text editor, preferably Notepad++.
Locate and delete any node starting with <data
Example. This is what you should delete.
<data name="$this.Icon" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
<value>
AAABAAMAICAAAAEAIACoEAAANgAAAGBgAAABACAAqJQAAN4QAACAgAAAAQAgACgIAQCGpQAAKAAAACAA
AABAAAAAAQAgAAAAAAAAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
///////////8AAB/////////
</value>
</data>
Reload or reopen your solution and build. You are ready to go.

Had the same problem after updating to VS 2017 v15.8.5, and none of the solutions above or on other forums worked for me.
So, since a .resx file is just XML, I just copied the content, deleted the original file and recreated it with the copied content.
That was the only thing that worked, and it worked first time.

A quick way to remove this mark of the web for multiple files and folders recursively for me was to
Zip them up.
Delete originals.
Unzip.

I'm not really sure either, I have the exact same issue.
But, what i did, was hit view in file explorer.
Then, i clicked show hidden items.
Finally, i went back to my folder and clicked on the .vs folder, my project/file name, v15, Server, sqlite3, and deleted DB.Lock.
I reopened the project, clicked build, and it worked perfectly.
This worked for me, it might/might not for you.

I also encountered this issue recently. The error began occurring after I set the icon of a Windows Form.
Researching for the cause and solution almost led me nowhere, because I did not download the icon from the internet, nor was I referencing a web-based icon file. It was stored entirely on my local machine.
After some more researching and digging around, I was able to figure out exactly what was causing the problem. I have Microsoft One-Drive installed on my machine. The directory in which the icon file was located is managed/synced by One-Drive. That fact was somehow tricking Visual Studio into believing the file was located or downloaded from the internet.
The solution proved to be very simple. I removed the icon from the form, as well as from the corresponding .resx file. Then I moved the icon file to another directory not associated with One-Drive. Finally, I was able to use that icon in my Windows Forms application without getting this error.
I understand there are other possible causes for this error. But if in your case, the issue happened after setting a form's icon--and if you have One-Drive (or perhaps another cloud-based storage solution) installed--then check to be sure that icon file is not in a directory managed by that service. If so, relocate it and change the form's icon property to point to the new location.

To fix this for multiple files within a project, Visual Studio -> Tools -> Options -> Trust Settings and add the project path as a trusted path.

Using VS 2019, and building against source stored on an Azure shared file system. I think I may have just tracked down a work-around, and it has to do with the Icon as referenced above by Jake above. If I add the icon to the form's resource file (that really long string), The error occurs.
However, if I add the Icon to the Project's resources, delete the Icon from the form's resource file, and change form to set the Icon manually...
this.Icon = MyProjectName.Properties.Resources.MyIcon;
The error goes away.

I found this solution on another forum. My project resided on a file share, so I had to enter file://[file share] for Step 4 below. I am running VS2019 on Windows 10.
Start Menu > type 'Internet Options'.
Select Local intranet zone on the Security tab then click the Sites button
Click Advanced button
Enter file://[computer name] or file://[file share]
Make sure 'Require server verification...' is unticked

I had the same issue in Windows 10 VS 2019 16.4.457 (previous version of VS 2019 had no problems).
The "marked for web" error shows only after I moved the project under One-Drive.
If I move the project back to a local drive the error doesn't show.
As Anthony Gingrich suggested, I tried to move the project images to a local directory without success.
The solution that works for me was, for each image, in the "Select Resource dialog" use "Project resource file" instead "Local resouce".

Please guys, I already fixed the issue, this is cause by OneDrive, please close your OneDrive with the use of task manager or close the icon OneDrive's Hidden Icons on the taskbar

I just ran into the same issue and also tried the Unblock option from explorer with no luck. I even restarted VS with no luck.
However, I'm not sure which combination did the trick but I opened the form as well as the resx file from within VS, just to see if I can open it, which opened fine. I then did a clean and rebuild and that appeared to do the trick. If it doesn't try restarting VS after the clean then rebuild.

I had a similar issue and the problem was an image that I had downloaded and added to my Resources. Not completely sure why that was the only image that gave me problems, however, I opened my abc.resx file giving me issues an a text editor, removed the node starting with " (it was the last and only node) just like Albert Alberto mentioned. Saved the changed, cleaned and rebuilt my solution and it all works! The image didn't render but it only took a second to go back and add the image. It wasn't removing the entire file, just the node that was causing the issue.

I had the same problem on Windows 10, VS 2017 (15.9.13). I sent myself a project from work through Dropbox so I could try a couple of things from home. But when I tried to build it VS gave me the 'marked for web' error.
After trying the solutions above without success I began experimenting. I was able to solve this by using the method listed above (right click -> properties -> unblock), but I had to do it for each of the images in the Resource folder--and I had to do EACH FILE individually since the 'unblock' option was not available on group-selects. I actually unblocked each source file in the project as well before trying to rebuild so I am not sure if both are required.
Its a bit of a pain--probably a huge pain for larger projects--but it absolutely got the project building again.
EDIT: I did find this article afterwards about unblocking entire folders--even recursively but have not tried it: https://www.winhelponline.com/blog/bulk-unblock-files-downloaded-internet/

None of these worked for me. I fixed it by converting the embedded base64 into a linked resource:
I found out the issue was with the embedded base64 image I had in the .resx (as the issue went away removing the data tag as explained in this question but that meant I removed the image) so I converted the embedded image into a .png file and made a link to that in the .resx.
To do that: open the .resx file in Visual Studio 2019 and double-click the image, and then click Ok and Yes in the following prompts that will appear so VS will convert the embedded image into a linked resource (sorry I can't upload pictures yet):
Hope it helps!
From my original comment.

"Error while trying to run project: Unable to start program". Can run program only once. Then VS needs restart

I'm running my .NET 4.0 (C#) project in debug mode after I start VS2013. It runs just fine.
The second time I start it from VS, I get the Dialog box that says "Error while trying to run project: Unable to start program C:\path\to\file.exe"
The process is still alive in the Taskmanager when I dismiss the dialog box.
From Windows Explorer, I can run the program just fine. And after closing it, the process is gone too from the Task Manager.
A rebuild doesn't help.
Is this a common problem with a known solution?

I had an issue similar to this and I had to clear the component cache instruction can be found Here.
Hope this helps.

For my case, it cause by Platform target, you could force choose it to x86 or x64 which your project is:
Each Project's Properties > Build > Platform target

As I pointed out also here, the only solution that worked for me was to disable the ConEmu integration:
ConEmu → Settings → Integration → Default term → disable Force ConEmu as default terminal for console applications
Some users reported that it was enough for them to disable the Aggressive mode in that same settings tab; that wasn't the case for me though.

The topic is old, but this might help someone else.
So in my case I made a file in Visual Studio with .cp extension (accidentally deleted the last 'p') this made visual studio just "include" the the file and not mark it as a compilation unit, thus not compiling it, I looked the *.vcxproj file in a text editor and found out about this, so if you open the project file in a notepad or something just find your file at the bottom usually and change from <Item .../> to <ClCompile .../>

I was getting similar errors. I just had to restart visual studio. Sometime couple times a day.

I had a similar error and resolved it by cleaning the solution. Right-click the solution name in Solution Explorer and choose Clean Solution.

I found a solution here:
Please check "Use Managed Compatibility Mode" under Tools|->Options->Debugging->General.

I'm Brazilian, I don't speak English very well. I did this translation on google translator.
I know the topic is old, but it can still help someone.
I had this same problem in the following situation, I have a dual boot computer (linux debian 11 and windows 10). Inside debian, on my NTFS D disk, I created a folder to perform programming tests. After accessing that same folder with windows, I created a new project in visual studio inside that same folder that I had created in linux. The creation of the project went without problems, however when I tried to run the project (F5), I received the same error from this topic. I tried all the solutions I found on the internet, and nothing worked. I gave all permissions to my admin user and it still didn't work. Then I realized that even going straight to the folder where the application's executable was and clicking directly on it, I still received the access denied error message. So, I took the project out of the folder I had created in linux, and it worked. So, what I could conclude, is that because the folder where my project was was created in linux, for some reason, my windows didn't trust this folder, so it didn't allow running executables from inside that folder, even this one executable having been created by visual studio from within windows.

Just simply create a folder name as "projects" in c drive and copy paste the newly created project in it. Run the project by doing clean & Build or Rebuild method . It will work

open the folder which contains the solution in visual studio.
again, open your *.sln file by double clicking it inside the solution explore once opened try running the solution or rebuild the solution. once rebuild gets completed, it will open without error from next time.

My way of solving the error : error while trying to load project : Unable to start program and c:\Path\to\file.exe was simply by
First restart Visual Studio
Click the build icon
Select the rebuild option
Run the Program or Debug the Program

This was a weird one. Going to put what happened to me here because it might happen to someone else. Everything was fine with the app until suddenly after some fairly insignificant code changes I suddenly started getting this error. Visual Studio was compiling the executable just fine. But, the moment I tried to run it (either from Visual Studio or directly) the executable file would be automatically deleted right out of the Debug folder. Super odd--never seen anything like it. I began to get suspicious that perhaps an anti-virus or the OS was somehow identifying a checksum or some signature in the executable as "dangerous". Or perhaps some obscure compilation bug was corrupting the executable. So on a hunch I made another innocuous change (added a couple of lines of code to color code some text in a rich text box) and the problem went away.

The Operation could not be completed. The system cannot find the path specified

I created a C# Website using Visual studio 2015 in my laptop, i copied the same folder to my desktop system and open in Visual studio 2015, when i try to run the application its suddenly gives following error.
The operation could not be completed. The system cannot find the path specified
Anybody feel same error in your latest Visual Studio 2015? I updated all the latest patches.
following trial are done
Re created the soluition file(.sln)
Deleted Web.config and added new one
Still the error exists, so i cant able to debug or run the application.

(1) Run VS as an admin (or elevated access) and open the solution.
(2) Set up a project as Start up Project (if you have multiple proj)
(3) Set up page as start up page.
this should help you run it

Create manually (Windows Explorer if necessary) a folder with name "Service References". Even if the folder does not appear in the Solution Explorer, is there.
Try adding the wsdl (xml) file again.

I had the same problem, resolved by creating a Connected Services folder in my project.
So juste create a Connected Services folder or a Service References folder in your project

I experienced this error. When I shorten the file path of the solution, the error disappear. I think you may put your solution to a folder with too long path name or your solution have some file with too long name.

I got a more specific project-load error message when I removed the project from the solution and tried to re-add it. In my case, it was because the URL/address of the application had changed in my local IIS. When I updated the tag in the .vbproj (or .csproj) file to the new value, then the project loaded successfully.

Visual Studio 2008: Added Project not showing up in Solution Explorer

SOLVED! For people who are having the same problem this is what i did:
I moved the project away from where Visual Studio though it would be. This forces you to create a new project file there. I did. Then i restarted the program and now my project was visible. I now just moved the original project-files into the now visible folder.
I added an project to my solution but it doesn't show up next to all the other imported projects.
And since it doesn't i'm unable to delete it and try again.
However it can be seen if i right click the solution and go to "Startup Project", "Project Dependencies" or "Debug Source File".
I have searched the web for a while now but have yet to find someone with a similar sutiation, how do i solve this?

I imagine that this is because the files don't exist. Have you created the project on a network drive somewhere? Have you renamed or moved the folder after adding it to the solution?
Check the paths are right, then double check. Also check your version control to ensure someone hasn't wiped out your changes and left the .sln file intact.
You can edit the .sln directly I suspect to double-check the exact path it's looking for. Verify that path exists too.
Make sure the project you added was created in the same version of Visual Studio too.

Visual Studio 2010 error building, due to missing files

I've searched everywhere and I can't seem to find anyone with the same problem (although I'm sure people have made the same mistake in the past)...I accidentally deleted the contents of my Debug and Release folders. Now I am getting file not found errors. As a background, it's a Windows Forms Application in C#, and I'm running Visual Studio 10.
Here's the errors:
Unable to read manifest 'bin\Debug\projectName.vshost.exe.manifest'
Could not find file [pathName]\projectName.vshost.exe.manifest.
Before I was missing the manifest, I was getting an error that it could not find the other contents of the folder (the exe, the pdb, etc.), error MSB3113 (link)
Things I've tried (and some of them were far-fetched, I know):
I tried renaming bogus files for all the missing files
I tried to find the deleted files, but can't
I tried deleting all the contents of the Debug/Release folders and doing a clean build
I tried deleting the Debug/Release directories
Let me know if you can think of anything I could try out. My issue seems to be vaguely similar to this one.

Here's how I ended up solving the problem - turns out I included my bin and obj directories in my project. For anyone experiencing the same problem, simply right click and "Exclude From Project." After doing this, clean and rebuild your project, and you should be good to go.

In my case the file app.manifest was checked-out. This file is located in my Winforms project under Properties folder. I selected this file from Pending Changes window and did "undo pending checkout". After that the build succeeded. This happened in Visual Studio 2008.

Worked for me: Properties => Build => Generate serialization assembly => change from Auto to Off