dynamic keyword in C#

Posted by in C# category on for Intermediate level | Points: 250 | Views : 3856 red flag

This article is to demonstrate use of dynamic keyword in c# .

New features of .NET 4.0

There are very popular new features came in .NET 4.0 .some of them are

Dynamic type

Named parameter

Optional Parameters 

Let's look into Dynamic type now

First of all check your .NET framework version in your development environment otherwise it will not work. If you are using visual studio 2010 then it’s fine, no need to worry.  And those who are using VS2008 or lower version please have a look on your .NET Version.

Let’s talk about Dynamic type in C#.

The bullet line about dynamic variable is “Everything will be in run time”. What does it mean ? It means that if you declare any object or variable as a dynamic type compiler will not bother about any operation associated with this object or variable. Getting confused?

 Please continue reading till this paragraph, I can assure you will understand. Take one example to understand it.  Suppose you have one variable declared dynamic type. And with this variable you want to do some restricted operation (some restricted operation, and you know compiler will not allow you), Then in compile time compiler will never complain you to do this operation but in run time it will show error. This behavior proves this statement “Everything will be in run time”.  Now let’s look practically.
static void Main(string[]
             dynamic DateTimeVariable = "Sourav";
             DateTime d = "Sourav";  //Show error Message

Here you can see when I was trying to assign a string to a DateTime variable then compiler is immediately complaining me but in case of   dynamic DateTimeVariable = "Sourav";. It’s not showing any error at compile time, though it will throw at run time.

See another more example of dynamic object

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Data;
using System.Diagnostics;
using System.Data.SqlClient;
namespace BlogProject
    class TestDynamic
        public void CallDynamic()
   class Program
        static void Main(string[] args)
             dynamic objD = new TestDynamic();
             objD.CallDynamic(100, 100);  //No error ,though function prototype mismatch

Here you can see I have created object of TestDynamic class called objD and using this object I am trying to call CallDynamic() function with two parameter as function argument  like

objD.CallDynamic(100, 100);

And in compile time my compiler is not complaining me at all. Because I have declared objD as a dynamic object . And we know all operation associated with dynamic object perform in run time.

Now, clear few concept of dynamic variable.

If you make some operation with loosely type variable(like var keyword) then the result will also be dynamic type. For example you are

         static void
Main(string[] args)
             dynamic value = 100;
             var newVal = value + 100;

If I try to get property or function of newVal variable (After operation with dynamic variable) I am not getting anything. But in general if I declare any var variable I can access any property in compile time itself because it convert into strong type in compile time itself.

You can assign anything in dynamic variable . Then difference between var and dynamic ?

Yes, you can assign any value in dynamic variable.  Like this

static void Main(string[]
             dynamic a = 100;
             dynamic b = "sourav";

Now, You may think in var also we can store any data. Then what is the difference between them ?  Difference is that

In var the type conversion operation performs in compile time and in case of dynamic it’s in run time.

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About the Author

Full Name: Sourav Kayal
Member Level: Silver
Member Status: Member,MVP
Member Since: 6/20/2013 2:09:01 AM
Country: India
Read my blog here http://ctrlcvprogrammer.blogspot.in/
I am .NET developer working for HelixDNA Technologies,Bangalore in healthcare domain. Like to learn new technology and programming language. Currently working in ASP.NET ,C# and other microsoft technologies.

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