What's the Difference between the Is and As operator in C#

“is” operator

 
In C# language, we use the “is” operator to check the object type. If two objects are of the same type, it returns true, else it returns false.
 
Let’s understand this in our C# code. We declare two classes, Speaker and Author.

1. class Speaker {    
2.     public string Name {    
3.         get;    
4.         set;    
5.     }    
6. }    
7. class Author {    
8.     public string Name {    
9.         get;    
10.         set;    
11.     }    
12. }    

Now, let’s create an object of type Speaker:

1. var speaker = new Speaker { Name=“Gaurav Kumar Arora”};    

Now, let’s check if the object is Speaker type:

1. var isTrue = speaker is Speaker;     

In the preceding, we are checking the matching type. Yes, our speaker is an object of Speaker type.

1. Console.WriteLine(“speaker is of Speaker type:{0}”, isTrue);   

So, the results are true.
 
But, here we get false:

1. var author = new Author { Name = “Gaurav Kumar Arora” };     
2. var isTrue = speaker is Author;     
3. Console.WriteLine(“speaker is of Author type:{0}”, isTrue);    

Because our speaker is not an object of Author type.
 
“as” operator
 
The “as” operator behaves in a similar way as the “is” operator. The only difference is it returns the object if both are compatible with that type. Else it returns a null.
 
Let’s understand this in our C# code.

1. public static string GetAuthorName(dynamic obj)     
2.   {     
3.      Author authorObj = obj as Author;     
4.      return (authorObj != null) ? authorObj.Name : string.Empty;     
5.   }     

We have a method that accepts a dynamic object and returns the object name property if the object is of the Author type. 
 
Here, we’ve declared two objects:

1. var speaker = new Speaker { Name=“Gaurav Kumar Arora”};   
2. var author = new Author { Name = “Gaurav Kumar Arora” };     

The following returns the “Name” property:

1. var authorName = GetAuthorName(author);     
2. Console.WriteLine(“Author name is:{0}”, authorName);    

It returns an empty string:

1. authorName = GetAuthorName(speaker);     
2. Console.WriteLine(“Author name is:{0}”, authorName);