Question

I want to know what exactly are the differences between CStr(), Str() and .ToString()?

Label1.Text = CStr(Int(Rnd() * 10))

and

Label1.Text = Str(Int(Rnd() * 10))

and

Label1.Text = Int(Rnd() * 10).ToString

If I use this condition:

If Label1.Text = "7" Then
     'Some code here
End If

Str() doesn’t work here. What’s the difference?

Answer 1

ToString will call the .ToString() function on a particular instance.
In practice, this means that it will throw an exception if the object in
question is Nothing. However, you can implement .ToString() in your own
classes to get a useful string representation of your object, whereas
CType/CStr only work with built-in classes and interfaces.

CStr and CType(expression, String) are exactly equivalent (I’m not
sure where the other poster got the idea that CStr is faster). But they
aren’t really functions, they’re compiler directives that will emit very
different code depending on the declaration of expression. In most
cases, these directives call a bunch of internal VB code that tries to
get a reasonable string out of expression.

DirectCast(expression, String) assumes that the expression in
question really is a String and just casts it. It’s the fastest of all
these options, but will throw an exception if expression is anything
other than a String.