c# - How to get an Interface Member name from Expression>

Question

I'm looking for a way to get the interface member name of the expression passed into Client.SendMessage. Below is what I've attempted, but I get an invalid cast exception.

public interface IFoo
{
    void Operation1(object data);
    void Operation2(object data);
}

public class FooClient<T>
{
    public void SendMessage(Expression<Action<T>> expr)
    {
        // InvalidCastException:
        // Cannot cast 'InstanceMethodCallExpressionN' to 'MemberExpression'
        var iMemberName = ((MemberExpression)expr.Body).Member.Name;

        Console.WriteLine(iMemberName);
    }
}

class Program
{
    static void Main()
    {
        var client = new FooClient<IFoo>();

        // Should write 'Operation1'
        client.SendMessage(x => x.Operation1("Hello, world!"));

        // Should write 'Operation2'
        client.SendMessage(x => x.Operation2("How are you?"));
    }
}

Answer 1

由于内部表达式是 a MethodCallExpression（而不是 a MemberExpression，它表示属性或字段访问表达式），您应该适当地对其进行强制转换并获取Method属性返回的 MethodInfo 对象的名称。

public class FooClient<T>
{
    public void SendMessage(Expression<Action<T>> expr)
    {
        var iMemberName = ((MethodCallExpression)expr.Body).Method.Name;

        Console.WriteLine(iMemberName);
    }
}