How do I get the custom attributes of a method from Action<T>?

Question

How can I get the custom attributes of a method from a Action<T> delegate?

Example:

//simple custom attribute
public class StatusAttribute : Attribute
{

    public string Message { get; set; } = string.Empty;
}

// an extension methodto wrap MethodInfo.GetCustomAttributes(Type, Bool) with
// generics for the custom Attribute type
public static class MethodInfoExtentions
{
    public static IEnumerable<TAttribute> GetCustomAttributes<TAttribute>(this MethodInfo methodInfo, bool inherit) where TAttribute : Attribute
    {
        object[] attributeObjects = methodInfo.GetCustomAttributes(typeof(TAttribute), inherit);
        return attributeObjects.Cast<TAttribute>();
    }
}

// test class with a test method to implment the custom attribute
public class Foo
{
    [Status(Message="I'm doing something")]
    public void DoSomething()
    {
        // code would go here       
    }
}

// creates an action and attempts to get the attribute on the action
private void CallDoSomething()
{
    Action<Foo> myAction = new Action<Foo>(m => m.DoSomething());
    IEnumerable<StatusAttribute> statusAttributes = myAction.Method.GetCustomAttributes<StatusAttribute>(true);

    // Status Attributes count = 0? Why?
}

I realize I could do this by using reflection on Foo, but for what I'm trying to create I have to use an Action<T>.

Answer 1

The problem is that the action doesn't directly point at Foo.DoSomething. It points at a compiler-generated method of the form:

private static void <>__a(Foo m)
{
    m.DoSomething();
}

One option here would be to change it to an Expression<Action<T>>, then you can dissect the expression tree afterwards and extract the attributes:

Expression<Action<Foo>> myAction = m => m.DoSomething();
var method = ((MethodCallExpression)myAction.Body).Method;
var statusAttributes = method.GetCustomAttributes<StatusAttribute>(true);
int count = statusAttributes.Count(); // = 1