Getting type or namespace name could not be found but everything seems ok

Question

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  amp  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

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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.

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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

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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

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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

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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

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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

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To solve this issue it can also help to delete and recreate the   sln DotSettings file of the associated solution

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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

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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

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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

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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

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Had the same errors  my story was following  after bad merging  via git  one of my  csproj files had duplicated compile entries like    lt Compile Include  Clients Tree cs    gt   lt Compile Include  Clients Car cs    gt   lt Compile Include  Clients Tree cs    gt           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

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Remove the assembly from GAC C  WINDOWS assembly folder - select your assebly and right click and uninstall   because solution keeps refference using guid and if that guid is in GAC  it will keep taking GAC version for compilation

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I was working on VS 2017 community edition and had the same issue with CefSharp nuget packages    Packages were downloaded and restored successfully  project could be built and run successfully - only the markup indicated that the namespaces were not recognized   All I had to do was to open the References section and click on one of the yellow exclamation signs      After a few seconds the markup errors went away

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In my case I went into the solution properties and made sure  Build  was checked in the Configuration for both projects  My main project didn t have it checked

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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

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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

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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

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I know its old  but I ve found the same issue  My project did build  I then updated Visual Studio to the latest  amp  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  amp  nothing had changed since it built OK  I cleaned the whole solution  amp  rebuilt it  it failed  I built the assembly on its own  it built OK  The project didnt build  I cleaned  amp  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

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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

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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

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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

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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

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In my case  I unload the project  then   Opened myProject csproj and update the ToolsVersion  quot 4 0 quot  to ToolsVersion  quot 12 0 quot  I m using vs 2017  using Paulus s answer https   stackoverflow com a 64552201 1594487    Deleted following lines from the myProject csproj   lt Import Project  quot    packages EntityFramework 6 4 0 build EntityFramework props quot  Condition  quot Exists     packages EntityFramework 6 4 0 build EntityFramework props   quot    gt   lt Import Project  quot   MSBuildExtensionsPath    MSBuildToolsVersion  Microsoft Common props quot  Condition  quot Exists    MSBuildExtensionsPath    MSBuildToolsVersion  Microsoft Common props   quot    gt     And the problem solved

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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

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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

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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

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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

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Struggled with this for a while  and not for the first time  In times past it usually was a configuration mismatch  but this time it wasn t   This time it has turned out to be that Auto-Generate Binding Redirects was set to true in my application   Indeed  if I set it to true in my library  then my library gets this error for types in the Microsoft Reporting namespace  and if I set it to true in my application  then my application gets this error for types from my library   Additionally  it seems that the value defaults to false for my library  but true for my application  So if I don t specify either one  my library builds fine but my application gets the error for my library  So  I have to specifically set it to false in my application or else I will get this error with no indication as to why   I also find that I will get this message regardless of the setting if a project is not using sdk csproj  Once I convert to sdk csproj  then the setting makes a difference   Also  in my case  this all seems to specifically have to do with the Microsoft ReportingServices ReportViewerControl Winforms nuget package  which is in my root library

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In my case  adding the dll as a reference gave the type or namespace name could not be found error  However  copying and pasting the dll file directly in bin folder resolved the error   No idea why this worked

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I got this error trying to make a build with a Visual Studio Team Services build running on my local machine as an agent   It worked in my regular workspace just fine and I was able to open the SLN file within the agent folder locally and everything compiled ok   The DLL in question was stored within the project as Lib MyDLL DLL and references with this in the csproj file    lt Reference Include  MYDLL  Version 2009 0 0 0  Culture neutral  PublicKeyToken b734e31dca085caa  gt     lt SpecificVersion gt False lt  SpecificVersion gt     lt HintPath gt Lib MYDLL dll lt  HintPath gt   lt  Reference gt    It turned out it literally just wasn t finding the file despite the hint path  I think maybe msbuild was looking relative to the SLN file instead of the project file   In any case if the message you get is Could not resolve this reference  Could not locate the assembly then make sure that the DLL is in an accessible location to msbuild   I kind of cheated and found a message that said Considered  Reference bin xxx dll  and just copied the dlls into there instead

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It event happen in Visual Studio 2017     Restart Visual Studio Clean project that fail to build  Rebuild the project

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I know this thread is old but anyway I m sharing  I have to install all third part dependencies of the imported assembly - as the imported assembly wasn t included as Nuget package thus its dependencies were missing   Hop this help

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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    lt ProjectReference Include  quot    Skin Skin csproj quot  gt     lt Project gt  1ad4b5d7-5014-4f5f-983e-2c59ac0e0028  lt  Project gt     lt Name gt Skin lt  Name gt   lt  ProjectReference gt    I then saved the Substrate csproj and the problem was solved  So as others have said this is a problem with VS tooling

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I got this error for  quot using System  quot  after adding a new library project to my VS2019 Solution   Adding the Package Newtonsoft Json currentversion  to the library project fixed the problem  because the dependencies for Newtonsoft Json included the NETStandard Library under Dependencies for the library and was producing a warning icon   The main project had an error until I installed Newtonsoft Json so I presumed that it would work for the Library too  and it did

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In my case  I had two project in a solution  I added a sub-namespace into the referenced project  but when building  I didn t notice that the referenced project build failed and it used the last successfully built version which didn t have this new namespace  so the error was correct  that it cannot be found  because it didn t exist The solution was obviously to fix errors in referenced project

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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

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Started having this problem after  downgrading  from VS 2019 Enterprise to VS 2019 Professional  Although the error was showing in the Error window  I could build the project without problems  Tried many solutions from this thread and others like equalizing target frameworks  delete and make the reference again  deleting  suo file  etc  What worked for me was simply deleting the project in my local repository and cloning it again from the remote repository

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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

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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

[c#] Getting "type or namespace name could not be found" but everything seems ok?

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