Question

I’m using Unity for interception. Because I have many interfaces I’m forced to using VirtualMethodInterceptor. In my behavior I would like to react only when the method called was declared in the particular type of interfaces (with special attribute). I thought that MethodBase.DeclaringType will solve my problem but it behaves different than I was hoping to. It returns implementing type.

I can agree that it makes sense as the method can be declared in multiple interfaces but there should be a way to easily get the list of them. Unfortunately I haven’t found it yet.

Small sample showing my problem

public interface ISample
{
    void Do();
}

public class Sample : ISample
{
    public void Do()
    {
    }
}

class Program
{
    static void Main(string[] args)
    {
        var m = typeof(Sample).GetMethod("Do") as MethodBase;
        Console.WriteLine(m.DeclaringType.Name); // Prints "Sample"
    }
}

one awkward solution:

var interfaces = from i in input.MethodBase.DeclaringType.GetInterfaces()
                where i.GetCustomAttributes(typeof(CustomAttribute), true).Length > 0
                where i.GetMethod(input.MethodBase.Name, input.MethodBase.GetParameters().Select(p=>p.ParameterType).ToArray()) != null
                select i;

Answer 1

The only solution I could come up with (similar to you not-so-awkward solution though).

public static bool IsMethodDeclaredInInterface(MethodBase method, Type myInterface)
{
    var methodType = method.DeclaringType;
    var typeFilter = new TypeFilter((t, crit) =>
                                        {
                                            var critTypes = crit as Type[];
                                            return critTypes != null && critTypes.Any(ty => ty.FullName == t.FullName);
                                        });
    var res = methodType.FindInterfaces(typeFilter, new[] {myInterface});
    return res.Length > 0;
}