I'm getting a:
type or namespace name could not be found
error for a C# WPF app in VS2010. This area of code was compiling fine, but suddenly I'm getting this error. I've tried removing the Project Reference and the using statement, shutting VS2010 and restarting, but still I have this issue.
Any ideas why this might be occurring, where it seems like I'm doing the right thing re Reference & using statement?
I also noted in VS2010 that intellisense for that namespace is working ok, so it seems like VS2010 has the project reference and is seeing the namespace on one hand, but during compile doesn't see it?
This can be the result of a .Net framework version incompatibility between two projects.
It can happen in two ways:
a client profile project referencing a full framework project; or
an older framework version targeting a newer framework version
For example it will happen when an application is set to target the .Net 4 Client Profile framework, and the project it references targets the full .Net 4 framework.
So to make that clearer:
Project A targets the Client Profile framework
Project A references Project B
Project B targets the full framework
The solution in this case is to either upgrade the framework target of the application (Project A), or downgrade the target of referenced assembly (Project B). It is okay for a full framework app to reference/consume a client profile framework assembly, but not the other way round (client profile cannot reference full framework targeted assembly).
Note that you can also get this error when you create a new project in VS2012 or VS2013 (which uses .Net 4.5 as the default framework) and:
the referencing project(s) use .Net 4.0 (this is common when you have migrated from VS2010 to VS2012 or VS2013 and you then add a new project)
the referenced projects use a greater version i.e. 4.5.1 or 4.5.3 (you've re-targeted your existing projects to the latest version, but VS still creates new projects targeting v4.5, and you then reference those older projects from the new project)
Reinstalling nuget packages did the trick for me. After I changed .NET Framework versions to be in sync for all projects, some of the nuget packages (especially Entity Framework) were still installed for previous versions. This command in Packages Manager Console reinstalls packages for the whole solution:
Update-Package –reinstall
I've no idea why this worked, but I removed the project reference that VS2015 was telling me it couldn't find, and added it again. Solved the problem. I'd tried both cleaning, building and restarting VS to no avail.
When building the solution I was getting the same error (type or namespace ' ' could not be found). Below it I saw a warning stating that "the reference could not be resolved" and to make sure "the assembly exists on disk".
I was very confused, because my DLL was very clearly in the location that the reference was pointing to. VS didn't seem to highlight any errors, until I tried to build the solution.
I finally realized the problem (or at least what I suspect was the problem). I was building the library file in the same solution. So even though it existed on the disk, it was being rebuilt in that location (somehow in the process of the library getting rebuilt my other project - in the same solution - that referenced the library must have decided that the library didn't exist)
When I right-clicked on the project and built that only, instead of the entire solution, I didn't get the error.
To fix this problem I added the library as a dependency to the project that was using it.
To do this:
I right-clicked on my Solution in the Solution Explorer and selected
"Properties"
Then in "Common Properties" I selected "Project Dependencies".
Then in the Projects drop-down menu I selected the project that
relied on the library, and
Checked the box next to the library found under "Depends On"
This ensures that the library project gets built first.
First I would verify that your project's generated information isn't corrupt. Do a clean and rebuild on your solution.
If that doesn't help, one thing I've seen work in the past for designer issues is opening up a windows forms project, then closing it again. This is a little chicken-entrails-ish, though, so don't hold your breath.
A trickier situation I ran into was:
Project one targets the 4.0 full framework with Microsoft.Bcl.Async package installed.
Project two target the 4.0 full framework but would not compile when reference a Project one class.
Once I installed the Async NuGet package on the second project it compiled fine.
In my case, I find the reference in the VisualStudio have a triangle, and a exclamation mark as this image,
then, I right click remove it, and add the dll reference correctly again, the problem was solved.
I had a similar issue: The compiler was unable to detect a folder inside the same project, so a using directive linking to that folder generated an error. In my case, the problem originated from renaming the folder. Even though I updated the namespace of all the classes inside that folder, the project info somehow failed to update. I tried everything: deleting the .suo file and the bin and obj folders, cleaning the solution, reloading the project - nothing helped. I resolved the problem by deleting the folder and the classes inside, creating a new folder and creating new classes in that new folder (simply moving the classes inside the new folder didn't help).
PS: In my case I was working on a web application, but this problem may occur in different types of projects.
This one worked for me. In your class, where the class name is defined, eg: Public class ABC, remove one character and wait a little. You error list will increase because you have changed the name. Now put back the character that you have typed. This worked for me, hopefully it will work for you too. Good Luck!!!
[Facepalm] My issue was that I had added the dependency in the C++ way of doing things.
Go to the project that won't build, open up the 'References' folder in Solution Explorer, and see if your dependency is listed.
If not, you can 'Add Reference' and choose the dependency on the Projects tab.
Boom Shankar.
Check the Build Action of the .cs file containing the missing type. Make sure it's C# compiler.
Click on the .cs file containing the missing type.
Press F4 to bring up Properties.
Make sure Build Action is set to C# compiler.
Before:
After:
It even happens in Visual Studio 2017.
Restart Visual Studio
Clean project that fails to build.
Rebuild the project.
Had the same errors, my story was following:
after bad merging (via git) one of my .csproj files had duplicated compile entries like:
<Compile Include="Clients\Tree.cs" />
<Compile Include="Clients\Car.cs" />
<Compile Include="Clients\Tree.cs" /> //it's a duplicate
If you have a big solution and more than 300 messages in the errors window it's hard to detect this issue.
So I've opened damaged .csproj file via notepad and removed duplicated entries. Worked in my case.
I had same problem as discussed: VS 2017 underlines a class in referenced project as error but the solution builds ok and even intellisense works.
Here is how I managed to solve this issu:
Unload the referenced project
Open .proj file in VS ( i was looking for duplicates as someone suggested here)
Reload project again (I did not change or even save the proj file as I did not have any duplicates)
We had a weird case of this that I just fixed in a solution. There was a hidden/whitespace character in front of a "using" statement in the main project. That project would build fine and the website worked fine, but the unit test project that referenced it could not be built.
I encountered this problem when upgrading existing projects from VS2008 to VS2012. I found that two projects (the only two that I created) were targeting different .Net Frameworks (3.5 and 4.0). I resolved this on the Application tab of the projects by making sure that both projects had ".NET Framework 4" in the Target Framework box.
In my case I had a Class that was listed in the proper source folder, but was not registering in Solution Explorer. I had to do right click the project > Add Existing item and manually select that Class it said it was missing. Then everything worked fine!
I know its old, but I've found the same issue. My project did build, I then updated Visual Studio to the latest & the project wouldnt build as it couldnt find a type definition from a separate assembly. The other assembly built OK, the main project referenced it correctly & nothing had changed since it built OK.
I cleaned the whole solution & rebuilt it, it failed. I built the assembly on its own, it built OK. The project didnt build. I cleaned & built multiple times, and it failed. I then called a colleague to look at it, when I built with him watching, it all built OK.
I think Visual Studio tooling is the problem, especially as I just updated it.
In my case, I unload the project, then:
Opened myProject.csproj and update the ToolsVersion="4.0" to ToolsVersion="12.0"(I'm using vs 2017)(using Paulus's answer https://stackoverflow.com/a/64552201/1594487).
Deleted following lines from the myProject.csproj:
<Import Project="..\packages\EntityFramework.6.4.0\build\EntityFramework.props" Condition="Exists('..\packages\EntityFramework.6.4.0\build\EntityFramework.props')" />
<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
And the problem solved.
You might also try eliminating the code you think you're having problems with and seeing if it compiles with no references to that code. If not, fix things until it compiles again, and then work your suspected problem code back in. Sometimes I get strange errors about classes or methods that I know are correct when the compiler doesn't like something else. Once I fix the thing that it's really getting hung up on, these 'phantom' errors disappear.
I know this is kicking a dead horse but I had this error and the frameworks where fine. My problem was basically stating that an interface could not be found, yet it build and accessed just fine. So I got to thinking: "Why just this interface when others are working fine?"
It ended up that I was actually accessing a service using WCF with an endpoint's interface that was using Entity Version 6 and the rest of the projects were using version 5. Instead of using NuGet I simply copied the nuget packages to a local repository for reuse and listed them differently.
e.g. EntityFramework6.dll versus EntityFramework.dll.
I then added the references to the client project and poof, my error went away. I realize this is an edge case as most people will not mix versions of Entity Framework.
Adding my solution to the mix because it was a bit different and took me a while to figure out.
In my case I added a new class to one project but because my version control bindings weren't set I needed to make the file writable outside of Visual Studio (via the VC). I had cancelled out of the save in Visual Studio but after I made the file writable outside VS I then hit Save All again in VS. This inadvertently caused the new class file to not be saved in the project..however..Intellisense still showed it up as blue and valid in the referencing projects even though when I'd try to recompile the file wasn't found and got the type not found error. Closing and opening Visual Studio still showed the issue (but if I had taken note the class file was missing upon reopening).
Once I realized this, the fix was simple: with the project file set to writeable, readd the missing file to the project. All builds fine now.
I had the same issue. One night my project would compile the next morning ERRORS!.
I eventually found out that visual studio decided to "tweak" some of my references and point them elsewhere. for example:
System.ComponentModel.ISupportInitialize somehow became "blahblah.System.ComponentModel.ISupportInitialize"
Quite a rude thing for vs to do if you as me
My case was same as discussed here but nothing solved it until I've removed the System.Core reference from the references list (Everything worked fine without it)
hope it will help someone because this issue is quite frustrating
To solve this issue it can also help to delete and recreate the *.sln.DotSettings file of the associated solution.
Ok, years later using VS 2017 .NET Core 2.2 Razor Pages I feel this answer might help someone.
If it was a snake it would have bit me.
I was throwing stuff around, changing names, renaming Models, and all of a sudden I got this error:
Error CS0246 The type or namespace name 'UploadFileModel' could not be
found (are you missing a using directive or an assembly reference?)
This was underlined in red in my .chstml Razor Page. (not underlined after fix):
#page
#model UploadFileModel
So, finally, and luckily, I found the code from someone else that I had originally used, and low and behold, the namespace did not include the .cshtml file name!!!
Here is my bad dummy error spank myself with the page name in the namespace:
namespace OESAC.Pages.UploadFile
{
public class UploadFileModel : PageModel
{
What my original code had and all I had to do was delete the page name from the namespace, UploadFile:
namespace OESAC.Pages
{
public class UploadFileModel : PageModel
{
And low and behold, all the errors disappeared!!
Silly me. But you know, MS has made this .NET C# MVC stuff really confusing for us non-computer scientists. I am constantly tripping on my shoelaces trying to figure out model names, page names, and syntax to use them. It shouldn't be this hard. Oh well. I hope error and solution helps someone. The error was right, there is no Namespace named "UploadFileModel" haha.
In my case the problem was that after changing namespace to exactly same as is in another project (intentionally), the name of assembly was changed as well by VS, so there were two assemblies with same name, one overriding the other
Had the same problem after merging some new code into a vs2019 project.
Restarted VS, unloaded and reloaded projects, ensured all projects in solution had same ToolsVersion= and TargetFrameworkVersion. None of this helped.
I had a case of project Substrate, failing to find namespace Skin (in project Skin).
Finally I opened up Substrate.csproj and checked all the ProjectReference Include entries. The others were there, but no reference to Skin, even though Skin did show up in the check box of the little project dependencies dialog. So the project dependencies dialog took the check box for Skin (and saved it somewhere) but did not alter Substrate.csproj. I then added the ProjectReference Include manually, ensuring I had the correct path and GUID for the skin project.
<ProjectReference Include="..\Skin\Skin.csproj">
<Project>{1ad4b5d7-5014-4f5f-983e-2c59ac0e0028}</Project>
<Name>Skin</Name>
</ProjectReference>
I then saved the Substrate.csproj and the problem was solved. So as others have said this is a problem with VS tooling
In my case I had a file built by external dependency (xsd2code) and somehow its designer.cs files were not processed by VS correctly. Creating a new file in Visual Studio and pasting the code in it did the trick for me.
To anyone that is getting this error when they try to publish their website to Azure, none of the promising-looking solutions above helped me. I was in the same boat - my solution built fine on its own. I ended up having to
Remove all nuget packages in my solution.
Close and reopen my solution.
Re-add all the nuget packages.
A little painful but was the only way I could get my website to publish to Azure.
I've got a project (project A)in vs2010 (c#) that I want to reference another project (.exe) (project B) that I created. Project A is a quick, down & dirty util that I will only use once but I need all the function calls and db calls from project B, so rather than cut, copy, pasting from one to another, I thought I could just reference project B in my references. I am able to point to the .exe and in code i can use it, but when I compile it, it complains about not being able to see it (the infamous "are you missing a using directive or assembly reference?" error).
Does anyone know how I can do this?
Most probably, also it's hard to say, you have .NET Framework version conflict. One of your projects has .NET Framework version which is not compatible with other.
Check in project properties of both of them the version of the framework.
Make them the same
Recompile both of them
and most probably the trouble will gone.
Hope this helps.
Make sure the namespace of classes you want to use from project A is included in the files in your project B in a using directive:
using projA.ExampleNamespace;
I have the same problem. When I first added the reference all worked fine. But some time later after a rebuild there were errors and the classes and namespaces of "project A" were not longer recognized. Removing and re-adding the reference solved the problem immediately (without rebuiling or anything). There were no errors in other code and all DLLs and EXEs were build correctly. Build Order and Build Dependency settings were also correct. Seems to be a strange bug in Visual Studio (I use 2013 Professional).
I also checked how the reference was set in csproj file. The csproj file didn't change at all after removing and re-adding the reference. Neither did the sln file.
Maybe it's some strange caching behavior. But as I used "Rebuild All" which cleans up temporary files imho, this shouldn't happen. Even restarting VS or the PC didn't help.
I've downloaded and compiled Amazon's .NET SDK for Mechanical Turk, producing two DLLs: Amazon.WebServices.MechanicalTurk.dll and Amazon.WebServices.MechanicalTurk.Domain.dll .
I then created a new WPF project and added the two DLLs as references. When I create objects from their space, Intellisense has no trouble browsing the assemblies- I can see the classes inside.
When I compile, however, I get an "type not found" error from the compiler. Intellisense no longer works for the Amazon namespace, and the DLLs have vanished from the Object Browser window inside Visual Studio, though they're still listed as references in Solution Explorer.
What's going on? I think I'm missing something obvious. I can see, for example, MTConfig, but when I try to instantiate it, it fails and I need to re-add the DLLs to try again.
Thanks!
How have you added the references? Did you copy the DLLs into your new project's output folder and add references to them there? I can imagine that giving the behaviour you describe, if VS wipes the output folder before a build. If that's what's happening, simply move the DLLs to a different directory (I typically create a "lib" directory) and point the reference there.
What I did to solve this same problem was to recompile the DLLs changing the .NET version from 2.0 to 4.0 in the project properties. Not sure why that works, but in my case it solved the issue.
When I add a reference to my dll in Visual Studio project, I am able to use it, but when I compile my code or try to run it, I get an are you missing a using directive or an assembly reference?_ Error. I am able to confirm that I have the right using statement for my namespace and I am able to confirm that the dll is correctly loaded.
Anyone have any idea what I may not have right in this?
Go to project settings and make sure that you are not compiling the project for a .net version that includes the text "client profile".
I had just had an issue precisely like this, even if this is an old question thought I would add my 2c on what fixed it as none of the other answers helped:
For whatever reason, when I built the solution top to bottom a certain dll was not getting updated and output that held changed code. So while my solution had no visible errors, when you attempted to build, it was still referencing the old dll and started complaining.
It was simply a case of directly re-building the offending project and after that it picked up the latest dll and built happily.
This seemed to be a freak accident as no configuration had changed between when it worked / when it didn't.
Sometimes, JUST REBUILD THE SOLUTION.
The location of the DLL is important.
If you add a reference on your local machine to a DLL that is outside of your Visual Studio solution, it isn't necessarily copied into your solution files (depends on the type of solution/project).
If this is your problem, then you need to either put the DLL in the same path on the other machine, or copy it into your solution so it gets deployed along with the solution files, and change the reference.
You can also handle this with build instructions, but that might be beyond your aspirations at the moment.
Most likely your dll is referencing another dll that the client project is not referencing and your dll code is exposing a type or an interface from the 3rd dll to the client code.
If you post the exaCt message, we'll be able to help better.
Are you using .net 4.0?
If yes, this dll is probably not compatible with .net 4.0
In my case, the main project (WinForm) was configured Framework Target: FW 4.0 "client profile". I change to FW 4.0 and work perfect!!.
At first time i was looking in the referenced projects and they were ok, but de main project doesn't. I hope this help. Thank you.
In my case this compilation error has gone after adding the reference to Microsoft BCL Build Components via "Manage NuGet packages" context menu on problem project.
Before: I had project Main (console application) referencing project A (class library).
Project A had dependency on Microsoft BCL Build Components.
After: I started refactoring where I picked out several classes to the separate project New. It also depended on A. But the compilation error occurred on project New as if there was no reference New -> A (although Visual Studio didn't highlight allegedly not found interfaces and classes listed in the error list of compilation).
So I checked project A's dependencies and found there Microsoft BCL Build Components.
After adding it to New's dependencies everything worked fine.
The most interesting thing is that Main did not contain this dependency and it didn't need it.
Hope this helps.
You just Have to check your namespace of that class file again...it will work
I've got a C# project in visual studio that is building a DLL, and another console project which includes the first as a reference. These are both in the same solution.
The trouble is when I add methods to the DLL, then rebuild the console project doesn't seem to pick them up.
For example, in the DLL I have a class Converters. If I add a method
public static void test() {}
it just doesnt' show up in the console app at all. Intellisense doesn't autocomplete it, and if I manually type it in it gives a compiler error.
If I go in and delete the dll files then rebuild that works (or better yet, delete the bin and obj directories) but that seems rather drastic.
I'm sure this is a basic error, but I can't seem to find the solution after some googling.
How are you adding the reference? As a project reference or by browsing to the DLL? If you're using the latter then it will copy it locally to the bin directory of your console app and won't refresh it unless you manually delete it. If you add it as a project reference it will copy it as and when it needs to.
The exact thing happened to me once on a project - it turned out the build command wasn't configured to build these DLLs.
Check Build - Configuration Manager, and make sure the project is checked:
(Image from msdb - Setting the Build Configuration)
close Project visualStudio and
rebuild again your dll (other project visualStudio)
One of the things to note is the Target Framework of the Projects, if you compile your Project A with target framework different then that of Project B and it is referencing the dlls of Project A you may run into this kind of trouble. So, make sure that the target framework for both Projects is same.
Check that you don't have the ddl inside the bin folder of your project. Whilst I was adding the reference by browsing for the dll, I had forgotten that I manually copy pasted a version into that folder. No matter how many times I cleaned and rebuilt, it didn't seem to update.
Deleting that dll and re-referencing fixed the issue.
Change the reference to the dll to the Project, instead of the output.
This is certainly unexpected behavior. It sounds like the reference between the two projects is broken in some way. Two issues come to mind.
Possible problem with the reference. Try deleting the reference in solution explorer and readding the reference and seeing if that fixes things. When you re-add make sure it's a project reference and not a file reference.
It's possible that the time stamps on the files in your project are off. See if they are in the future.
check the folder which contains the reference. does it contain a refresh file with a relative path in it? if so, and if assembly names in the location pointed to by the relative path are common with those in of (project) references which should auto update, then these references no longer auto update! what you end up is a static reference to the assemblies present in the relative path contained in the refresh file.
you may also have to delete the projectreferences key in the sln file and add references afresh
I hate to beat a dead SO question but 8 years after the original question and none of the above solving the issue for me, my problem was in VS2013, but to solve it I simply removed and re-added the reference to the DLL in the project that invokes it.
I hope this helps some people in the newer VS realm having the same issue.