Question

The following code gives me the warning Contract class 'FooContracts' should be an abstract class. From all the examples I’ve read online (e.g. http://www.infoq.com/articles/code-contracts-csharp), this should work (presumably without compiler warnings).

[ContractClass(typeof(FooContracts))]
public interface IFoo {
  void Bar(string foo);
}

[ContractClassFor(typeof(IFoo))]
internal sealed class FooContracts : IFoo {
  void IFoo.Bar(string foo) {
    Contract.Requires(foo != null);
  }
}

I’m in Visual Studio 2010, with the following settings in the Code Contracts section of the project’s properties:

• Perform Runtime Contract Checking (set to Full)
• Perform Static Contract Checking (under Static Checking)
• Check in Background

I also defined the CONTRACTS_FULL compilation symbol to make ReSharper shut up.

Am I missing something to make this compile without warnings?

Answer 1

Section 2.8 of the code contracts manual specifically states that it should be an abstract class:

The tools expect that the contract class is abstract and implements the interface it is providing contracts
for.