C# Dynamic Type

In c# 4.0, the new dynamic type has been introduced to bypass the type checking at compile-time. Instead, it will resolve the type at runtime. In c#, the dynamic type is same as implicitly typed local variable var, but the only difference is the type checking will happen at runtime.

 

We can define dynamic type variables using a dynamic keyword like as shown below.

 

dynamic x = 50;
dynamic y = 10.25;

In the above declarations, we used a dynamic keyword to define the dynamic variables. In most cases, the compiler will compile the variables of dynamic type into the object type variables, but the compiler does not resolve those during compile-time; instead, those will evaluate at run time.

 

The above dynamic declarations will be compiled into object types during compile-time, as shown below.

 

object x = 50;
object y = 10.25;

As discussed, the actual type will assign to the dynamic variables at runtime based on the right-side value of the initialization statement.

C# Dynamic Type Example

The following example will show how to declare dynamic variables and how a dynamic variable will change its type based on the right-side value of its initialization statement.

 

using System;

namespace TutlaneExamples
{
    class Program
    {
       static void Main(string[] args)
       {
          dynamic i = 100;
          Console.WriteLine("i value:{0}, type: {1}", i, i.GetType());
          dynamic j = "Welcome to Tutlane";
          Console.WriteLine("j value:{0}, type: {1}", j, j.GetType());
          dynamic k = true;
          Console.WriteLine("k value:{0}, type: {1}", k, k.GetType());
          dynamic l = 20.50;
          Console.WriteLine("l value:{0}, type: {1}", l, l.GetType());
          Console.ReadLine();
       }
    }
}

If you observe the above example, we declared and initialized the dynamic variables with different values. The actual type will assign to the dynamic variables at runtime based on the right-side value of the initialization statement.

 

When we execute the above example, we will get the result as shown below.

 

i value:100, type: System.Int32
j value:Welcome to Tutlane, type: System.String
k value:True, type: System.Boolean
l value:20.5, type: System.Double

C# Dynamic Type as Method Parameter

If we use dynamic type as a method parameter, then it will accept any type of parameter at run time.

 

Following is the example of using dynamic type as a method parameter in c#.

 

using System;

namespace TutlaneExamples
{
    class Program
    {
       static void Main(string[] args)
       {
          GetDetails(100);
          GetDetails("Welcome to Tutlane");
          GetDetails(true);
          GetDetails(20.50);
          Console.ReadLine();
       }
       static void GetDetails(dynamic d)
       {
          Console.WriteLine(d);
       }
    }
}

If you observe the above example, we defined the GetDetails method with a dynamic parameter so it will accept any type of parameter; that’s why we call the GetDetails() method by sending different types of values.

 

When we execute the above example, we will get the result as shown below.

 

100
Welcome to Tutlane
True
20.5

C# Assign Class Object to Dynamic Type

In c#, if we assign any class object to a dynamic type, the class object properties and methods will be exposed only at runtime. So, the compiler will not throw an exception even if we try to access the methods or properties which do not exist in the class.

 

Following is the example of assigning the class object to dynamic type and accessing properties and methods in c#.

 

using System;

namespace TutlaneExamples
{
    class Program
    {
       static void Main(string[] args)
       {
          dynamic dobj = new User();
          dobj.GetInfo();
       }
    }
    class User
    {
       public int Id { get; set; }
       public string Name { get; set; }
       public void GetDetails(dynamic d)
       {
          Console.WriteLine(d);
       }
    }
}

If you observe the above example, we created a dynamic variable “dobj” and assigned the User class object. We tried to access the GetInfo() method that does not exist in the User class. However, the compiler will not throw an exception because it will skip the type checking for dynamic type during compile time, but we will get a runtime exception as shown below.

 

C# Assign Class Object to Dynamic Type Example Result

 

C# Dynamic Type Overview

The following are the important points that we need to remember about dynamic type in c#.

 

  • The dynamic type is useful to bypass the type checking at compile-time. Instead, it will resolve the type at runtime.
  • During compile-time, the compiler will compile the dynamic type variables into the object type variables.
  • If we use dynamic type as a method parameter, then it will accept any type of parameter at run time.
  • Visual studio will not provide any IntelliSense support for dynamic types.
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