FullErrorReturn.cs

void ErrorReturn(MethodInterceptionArgs args)
{
    try
    {
        var methodInfo = args.Method as MethodInfo;
        if (methodInfo == null)
            return;
        if (methodInfo.ReturnType == typeof(string))      // if it's string, just return a null
            args.ReturnValue = null;
        else if (typeof(IEnumerable).IsAssignableFrom(methodInfo.ReturnType))
            args.ReturnValue = Activator.CreateInstance(methodInfo.ReturnType);
        else if (methodInfo.ReturnType.IsValueType)       // for value types, return default
            args.ReturnValue = Activator.CreateInstance(methodInfo.ReturnType);
        else if (methodInfo.ReturnType != typeof (void))  // anything else, return null
            args.ReturnValue = null;
    }
    catch
    {
        // don't want any errors to take place trying to build the correct return value
        // so just swallow them, and let args.ReturnValue stay whatever it is
    }
}