调用类方法而不是扩展方法

Question

I'm working with the MongoDB C# Driver and NSubstitute. I need to mock the FindAsync method on the IMongoCollection class. The problem is that there is a IMongoCollectionExtension class with the exact same signature . When I attempt to mock the FindAsync method it calls the extension method which throws an exception due to the Ensure.IsNotNull call.

Is there a way to ensure the class method is called rather than the extension method? It's not working that way now. They are even in the same namespace.

Example of how I'm trying to call it via my test.

        _collection = Substitute.For<IMongoCollection<DirectoryObject>>();
        _database.GetCollection<DirectoryObject>(Constants.DirectoryObjectCollection).Returns(_collection);
        _collection.FindAsync(Arg.Any<FilterDefinition<DirectoryObject>>(), null, default(CancellationToken)).Returns(cursor);

Method Signature:

Task<IAsyncCursor<TProjection>> FindAsync<TProjection>(FilterDefinition<TDocument> filter, FindOptions<TDocument, TProjection> options = null, CancellationToken cancellationToken = default(CancellationToken));

Extension Method Signature:

public static Task<IAsyncCursor<TDocument>> FindAsync<TDocument>(this IMongoCollection<TDocument> collection, FilterDefinition<TDocument> filter, FindOptions<TDocument, TDocument> options = null, CancellationToken cancellationToken = default(CancellationToken))

Screenshot of the IntelliSense suggesting I'm calling the extension method.

EDIT:

Changing the mocked method call to this fixes the issue. The signatures aren't exactly the same. The extension doesn't have a different projection and document type.

        _collection.FindAsync<DirectoryObject>(Arg.Any<FilterDefinition<DirectoryObject>>(), null, default(CancellationToken)).Returns(cursor);

Answer 1

For reference if anyone else thinks they have this problem, you don't! On a naming clash between an instance method and an extension method, it is the instance method is called.

If you do need preferentially select which method is called, you actually have the reverse problem which is to call the extension method directly using it's declaring class.

eg with a name clash like this:

public static class ObjectExt 
{ 
    public static string ToString(this object o) => ""; 
}

you can disambiguate as:

instance.ToString(); // call the instance method

ObjectExt.ToString(instance); // call the extension method