Difference between casting and as?

Question

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What is the difference between the following casts in c#?

In C#, is a there difference between casting an object or using the as keyword? Hopefully this code will illustrate what I mean...

String text = "Hello hello";
Object obj = text; 

String originalCast = ((String)obj).ToUpper();
String originalAs = (obj as String).ToUpper();

Answer 1

as will never throw a InvalidCastException. Instead, it returns null if the cast fails (which would give you a NullReferenceException if obj in your example were not a string).