c# - Difference between is and as keyword

Question

Please tell what is the difference between is and as keyword in C#

Answer 1

is

The is operator checks if an object can be cast to a specific type.

Example:

if (someObject is StringBuilder) ...

as

The as operator attempts to cast an object to a specific type, and returns null if it fails.

Example:

StringBuilder b = someObject as StringBuilder;
if (b != null) ...

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Also related:

Casting

The cast operator attempts to cast an object to a specific type, and throws an exeption if it fails.

Example:

StringBuilder b = (StringBuilder)someObject.