What is the difference between IS and AS keyword in C#?

In C#, both the "is" and "as" keywords are used for type checking and type casting, but they serve different purposes:

1. is Keyword:
   • The "is" keyword is used for type checking. It returns true if an object is of a specified type, otherwise false.
   • It is primarily used in conditional statements or expressions to check if an object is compatible with a certain type before performing operations on it.
   • The syntax is object is Type.

Example:

object obj = "Hello";
if (obj is string)
{
    // obj is a string, perform string operations
}

2. as Keyword:
   • The "as" keyword is used for explicit type casting (converting one type to another). If the conversion is possible, it returns the converted type; otherwise, it returns null.
   • It's primarily used to safely attempt casting an object to a specific type without throwing an exception if the cast fails.
   • The syntax is expression as Type.

Example:

object obj = "Hello";
string str = obj as string;
if (str != null)
{
    // Successfully casted to string, perform string operations
}
else
{
    // obj is not a string
}

In summary, "is" is used for type checking while "as" is used for type casting with a safe null check.