Question

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Why use TryCast instead of DirectCast?

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

Answer 1

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.