How do I check type of dynamic datatype at runtime?

Question

In my ASP.NET website, I have a method that returns a value of type dynamic. This method, depending on certain criteria and results, will then either return a Boolean value or SortedList.

There is too much code to paste, but for example:

public dynamic ReturnThis(dynamic value)
{
    if(someConditionIsMet)
    {
        value = true;
    }
    else
    {
        value = new List<String>().Add(new Person() { Name = "Travis" });
    }

    return value;
}

My problem is, I would like to determine the datatype of value after calling this method before acting on or reading its data. But I am unsure how to check what type dynamic value is. How can I do this?

Answer 1

Both solutions are working for me. In the documentation Smeegs linked to, the is keyword was mentioned. And I came up with a slightly more readable solution:

if(value is Boolean) { } and if(value is List<Person>) { }

---

A working test:

using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;  namespace ConsoleApplication3348 {     class Program     {         class Person         {             string Name = "";         }          static void Main(string[] args)         {              Console.WriteLine("Assigning List to value");             dynamic value = new List<Person>();              if (value is List<Person>)             {                 Console.WriteLine("value is a list");             }              value = false;              Console.WriteLine("Assigning bool to value");             if (value is Boolean)             {                 Console.WriteLine("value is bool");             }              Console.Read();         }     } } 

Answer 2

Just read this on another SO question...hopefully it will do the trick for you:

Type unknown = ((ObjectHandle)tmp).Unwrap().GetType(); 

Read and upvote this question for more info: get the Type for a object declared dynamic

Answer 3

You should just be able to use GetType(). Like so:

dynamic returnedValue = ReturnThis(value);
var returnType = returnedValue.GetType();

Here is some more information on GetType()

Answer 4

Given a dynamic type:

dynamic dynVar;
Type type; 

A merely declared, uninitialized dynamic variable dynVar will throw an exception of Type Microsoft.CSharp.RuntimeBinder.RuntimeBinderException as you are performing runtime binding on a null reference, when performing Type-Reflection via dynVar.GetType().

• As pointed out by "Troy Carlson", one may use, the rather slow method via a remoted MarshalByRefObject:

   Type type = ((ObjectHandle)dynVar).Unwrap().GetType();
   // > type...is null
  

• But a simple null check as for any other type would suffice:

   type = dynVar == null ? null : dynVar.GetType();
  

• or...

   type = dynVar?.GetType();