How should I cast in VB.NET?

Zack Peterson picture Zack Peterson · Sep 2, 2008 · Viewed 160k times · Source

Are all of these equal? Under what circumstances should I choose each over the others?

  • var.ToString()

  • CStr(var)

  • CType(var, String)

  • DirectCast(var, String)


EDIT: Suggestion from NotMyself

  • TryCast(var, String)

Answer

bdukes picture bdukes · Sep 3, 2008

Those are all slightly different, and generally have an acceptable usage.

  • var.ToString() is going to give you the string representation of an object, regardless of what type it is. Use this if var is not a string already.
  • CStr(var) is the VB string cast operator. I'm not a VB guy, so I would suggest avoiding it, but it's not really going to hurt anything. I think it is basically the same as CType.
  • CType(var, String) will convert the given type into a string, using any provided conversion operators.
  • DirectCast(var, String) is used to up-cast an object into a string. If you know that an object variable is, in fact, a string, use this. This is the same as (string)var in C#.
  • TryCast (as mentioned by @NotMyself) is like DirectCast, but it will return Nothing if the variable can't be converted into a string, rather than throwing an exception. This is the same as var as string in C#. The TryCast page on MSDN has a good comparison, too.