Red Swan Red Swan - 2 months ago 15
Vb.net Question

What is TryCast and direct cast in VB.NET?


Possible Duplicate:
Why use TryCast instead of DirectCast?




I want to know about TryCast and DirectCast in VB.NET. What is the difference between them?

Answer

The main difference between TryCast and DirectCast (or CType) is that both CType and DirectCast will throw an Exception, specifically an InvalidCastException if the conversion fails. This is a potentially "expensive" operation.

Conversely, the TryCast operator will return Nothing if the specified cast fails or cannot be performed, without throwing any exception. This can be slightly better for performance.

The MSDN articles for TryCast, DirectCast and CType say it best:

If an attempted conversion fails, CType and DirectCast both throw an InvalidCastException error. This can adversely affect the performance of your application. TryCast returns Nothing (Visual Basic), so that instead of having to handle a possible exception, you need only test the returned result against Nothing.

and also:

DirectCast does not use the Visual Basic run-time helper routines for conversion, so it can provide somewhat better performance than CType when converting to and from data type Object.