C# Is Operator C# has an interesting operator know as is. The is operator is used for execution-time type checking. It is a binary operator that returns a Boolean

Is Vs As Operator Keyword In C#

The is operator is used to check if a type of an object is compatible with the given type at the run-time,

1 if(obj is SomeClass)

2 {

3 ...

4 }

whereas, as operator is used to perform casting between compatible reference types or Nullable types.

1 SomeClass someObject = obj as SomeClass;

With the “classic” method of type casting,

1 SomeClass someObject = (SomeClass) obj;

if the cast fails, an exception is thrown. However, with the as method, it results in null, which can be checked for, and avoid an exception being thrown.

1 SomeClass someObject = (obj as SomeClass) ?? new SomeClass();

Note: you can only use as with reference types, so if you are typecasting to a value type, you must still use the “classic” method.

Further Reading

• 
  C# Variable Types - C# is a type-safe language. Variables are declared as being of a particular type, and each variable is constrained to hold only values of its declared type. Variables can hold either value types or reference types, or they can be pointers. This lesson covers the value types and reference types.
  
• 
  Generics In C# - This article explains the Generics in C# with the help of a real-time problem and its step by step solution using c# generics. This article serves to be an in-depth post on getting started with generics in c#.
  
• 
  Writing Implicit and Explicit C# Conversion Operators by Jason Roberts - When writing custom classes we can provide behavior to allow for both explicit and implicit conversions to other types. Implicit conversion operators are those that don’t require an explicit cast. Explicit conversion operators are those that do require an explicit cast. In this article, Jason explains how to write them.
  
• 
  Nullable Types And Null Coalescing Operator C# - A reference type can have an actual value of null, meaning it has no value. A value type can’t have a value of null. This is why Nullables were added to the .Net Framework. This C# article discusses the Nullables with Null Coalescing operator and also explains the unique ways to use the Null Coalescing operator.