Adding an interface to a partial class

Question

I have a class that is generated by a third party tool:

public partial class CloudDataContext : DbContext 
{
    // ...SNIPPED... 
    public DbSet<User> Users { get; set; } 

}

I create a partial class and then assign an interface so that I can inject this class later:

public partial class CloudDataContext : IDataContext
{

}

The IDataContext has the single property Users.

This won't compile, the compiler complains that the interface isn't implemented.

If I move the interface to the generated class, it works fine. I can't do that though as it's generated code.

How can I apply an interface to a partial class to expose the class as defined above?

Can you show the definition of `IDataContext` and the implementation of `CloudDataContext`? I just ran [this example](http://dotnetfiddle.net/ExiSIp) and it works just fine. — Jeroen Vannevel, Dec 11 '13 at 00:37
I'm going to go out on a pretty far limb here: are the `using` directives at the top of the two class files different? Is it possible that in the one code file, `IDataContext` resolves to _one_ interface, and in the other code file `IDataContext` resolves to a _second different_ interface? — Chris Sinclair, Dec 11 '13 at 01:01

score 31 · Accepted Answer · edited Jan 17 '22 at 14:37

31

The problem must be somewhere else, because you can implement interface in the other part of partial class than it's set on. I just tried following and it compiles just fine:

public interface IFoo
{
    int Bar { get; set; }
}

public partial class Foo
{
    public int Bar { get; set; }
}

public partial class Foo : IFoo
{

}

The properties probably use different types in interface and class.

edited Jan 17 '22 at 14:37

General Grievance

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answered Dec 11 '13 at 00:35

MarcinJuraszek

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Turns out it was a typo in the name space of one of the partials. Once matched, it worked. – Ian Vink Dec 11 '13 at 18:58
3

In my case it was because the new partial class file I generated had a different class name. Remember to change the class name to match the one in the other file... – Andrew Sep 09 '18 at 00:56

score 4 · Answer 2 · answered Nov 13 '18 at 20:08

Here's a quick checklist. Do the classes have identical:

Names?
Namespaces?
Access modifiers?

Example:

You decide to split an existing class into two files.
The original file's namespace doesn't match its folder path.
Consequently, the new class file you create has a mismatching namespace.
Build fails.

score 1 · Answer 3 · answered Oct 23 '20 at 07:39

1

IN my Case problem was that interface Method that was implemented in other part of the partial class was not compiling and C# was giving error of not implemented Method

answered Oct 23 '20 at 07:39

Veacelsav Dragancea

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score 0 · Answer 4 · answered Jun 20 '21 at 17:36

In my case, the interface method signature didn't mention a value (uint direction) that the actual method expected. This showed up as the interface having errors in one of the partial classes. Make sure that the interface for a method is actually the same as the method signature itself. D'oh.

score 0 · Answer 5 · answered Jun 25 '23 at 16:44

0

Make sure that all files of the partial class have "C# compiler" Build Action in VS.

answered Jun 25 '23 at 16:44

Greg Z.

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Adding an interface to a partial class

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