Warning “The type X in Y.cs conflicts with the imported type X in Z.dll”
Asked Answered
Z

11

48

The main.cs of my project returns the following warning:

Warning 1 The type 'Extensions.MessageDetails' in 'PATH\Extensions.cs' conflicts with the imported type 'Extensions.MessageDetails' in 'path\lib.dll'. Using the type defined in 'path\Extensions.cs'. path\main.cs

What is wrong with my project? How to get rid of the warning?

The code of my project has the following structure:

Extensions.cs

namespace Extensions
{

    public class MessageDetails
    {
        public string message { get; set; }
        public string link { get; set; }
        public string picture { get; set; }
        public string name { get; set; }
        public string caption { get; set; }
        public string description { get; set; }
        public string userid { get; set; }
        public string username { get; set; }

        public object actions { get; set; }
        public object privacy { get; set; }
        public object targeting { get; set; }
    }

}

lib.dll

namespace MyClassLib {

    public class MyClassLibFoo {
        public void foo(MessageDetails parameters) {
            /* .. */
        }
    }

}

main.cs

using MyClassLib;
using Extensions;

class Program
{
    static void Main(string[] args)
    {
        MessageDetails md = new MessageDetails();
    }
}
Zebulun answered 10/11, 2011 at 0:59 Comment(4)
Are there two copies of your extensions class (one packaged in your dll and one in your main program)?Gerald
yes,I need use the MessageDetails in namespace Extensions class..Zebulun
That is your problem, they both need to reference the same one. Try adding it to a class library to do this.Gerald
This happened to me in an ancient webforms project in Visual Studio 2015 such that code in App_Code was being compiled twice which made it ambiguous.King
B
38

It seems like Extensions.cs is both part of the project that builds lib.dll and your main.exe

Remove it from one of the project to fix this issue.

Butch answered 10/11, 2011 at 1:7 Comment(3)
ty, for some reason, vs added my project as a reference.Turpeth
Was going nuts why we had this, never realized was possible!Brodsky
yeap. I don't know how my project referenced itself and causes a bunch of errorsJeanninejeans
E
70

In my case, with Visual Studio 2013, I found that one of my class libraries had developed a reference to itself. I think it happened when I added a new project to my solution or it was a bug, but either way it was causing this exact issue.

Check your project references for any circular references.

Eddieeddina answered 21/4, 2015 at 22:1 Comment(5)
I found this to be the cause of this error for me as well. That is quite strange.Contrapose
Still seems to be an issue in vs 2015 as this was my exact issue.Century
Good answer. Just to add to this first thing to check is your references for the project so expand this in Solution Explorer and you will probably find that your project itself is added as a reference, select it and remove it. My problem occurred beacuse of ReSharper where I had used the refactor tools in various places and somehow managed to add the project as a reference.Mammal
This happened for me in Unity and VSCode when Duplicating a ScriptableObject, and then renaming the file and the class definition. Restarting VSCode resolved it.Reinstate
This fixed the issue for me in VS2017 my guess is based on above comments it is ReSharper and spurious Alt-Enter adding references.Bolyard
B
38

It seems like Extensions.cs is both part of the project that builds lib.dll and your main.exe

Remove it from one of the project to fix this issue.

Butch answered 10/11, 2011 at 1:7 Comment(3)
ty, for some reason, vs added my project as a reference.Turpeth
Was going nuts why we had this, never realized was possible!Brodsky
yeap. I don't know how my project referenced itself and causes a bunch of errorsJeanninejeans
A
13

I had this kind of issue where I had reverted from a target .NET Framework version of 4.5.2 to 4.0.

Classes in my App_Code folder had methods that called methods in other classes in that folder. When I created a standard folder I named "AppCode", and moved my classes into it, I no longer had the issue.

If I re-created the "App_Code" folder and move my classes back into it, I will have this issue again. I'm convinced it has to do with my .NET Framework version or that Visual Studio just doesn't deal well with changing it after being initially built/targeted to another version.

Atoll answered 15/6, 2016 at 21:48 Comment(2)
Exactly what helped me to resolve this strange behavior in VS2017 with framework version 4.5.2. Studio showed crazy warnings I'm using C#6 features in C#5 project, and types in that folder was conflicting with imported themselves, and linq statements was missing something and ReSharper has only the rename refactoring on methods in the class.Erny
@Erny Yep - it will lose references to classes.Atoll
G
4

You can't have two copies of the extensions class, even though the code is the same they are not seen as the same object. Both your dll and main application will need to reference the exact same one.

You could try creating a 'Common Files' class library and add the extensions class to it, that way you will always be using the correct class

Gerald answered 10/11, 2011 at 1:12 Comment(0)
P
3

If you really need to have both classes declared or referenced in two separate dll, you can mark your class as internal.

Internal types or members are accessible only within files in the same assembly, therefore it will prevent the collision.

Providential answered 9/5, 2017 at 15:40 Comment(0)
C
2

I had this problem with a project that is also hosted on NuGet. I checked all project references. Finally, the object browser revealed that the DLL of an older version of my NuGet package was somehow loaded in Visual Studio from the NuGet cache folder ("C:\Users\{username}\.nuget\packages"). I removed the package from the cache folder, it disappeared from the object browser and everything was working fine again.

Construe answered 25/2, 2016 at 17:53 Comment(0)
S
2

I had a Shared Project, "Project A," which was included in both "Project B" and "Project C."

"Project A" was added as a Shared Project in "Project B" and "Project C."

"Project A" also included a traditional reference to "Project B."

To correct the problem, I removed the reference to "Project B" from "Project A."

Somme answered 19/3, 2017 at 23:54 Comment(0)
V
2

After reading through many answers on SO the solution was still unclear. My situation was similar but the solution was found by:

Example project Name: My.Example.Project

  1. Opening my project
  2. Open the References dropdown
  3. Finding My.Example.Project in the References section
  4. Deleting the reference to My.Example.Project

That fixed it!

Valma answered 18/6, 2021 at 14:22 Comment(0)
A
1

I had faced same problem. Just a simple solution for that.

Check your project references there must be same project reference. just remove that, it will work.

Aloysius answered 3/8, 2017 at 7:22 Comment(0)
P
1

sometimes I get this error - it's a bug though in my case.. All I have to do to fix it is change the first letter of my script file name from upper case to lowercase in the file in Explorer / (or in Unity Engine in my case) and then change the name / class accordingly in my script. Idk why this happens.. just does - and Idk why this fix works .. but in my case it always does. - Otherwise you probably have 2 copies of the same script / same class name for 2 diff scripts. Hope this helps.

Photosphere answered 7/4, 2018 at 13:18 Comment(0)
A
0

I fixed this error by deleting the .suo file in the directory sturcture vs directory. stop vs then delete restart vs. that worked for me.

Andersen answered 26/9, 2022 at 17:31 Comment(0)

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