What is the difference between "object as type" and "((type)object)"? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

Direct casting vs 'as' operator?

Casting vs using the 'as' keyword in the CLR

object myObject = "Hello world.";
var myString = my开发者_开发知识库Object as string;

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object myObject = "Hello world.";
var myString = (string)myObject;

I have seen type conversion done both ways. What is the difference?

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"as" will set the result to null if it fails.

Explicit cast will throw an exception if it fails.

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var myString = myObject as string;

It only checks the runtime type of myobject. If its string, only then it cast as string, else simply returns null.

var myString = (string)myObject;

This also looks for implicit conversion to string from the source type. If neither the runtime type is string, nor there is implicit conversion, then it throws exception.

Read Item 3: Prefer the is or as Operators to Casts from Effective C# by Bill Wagner.

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The cast will throw an exception if the object cannot be cast to the target type. as will just return null.