CStr() Str() .ToString()

Question

I just want to know, what exactly the difference between the functions CStr() and Str() and also the .ToString()? With the code provided below, what's the difference between the three?

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

and

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

and

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

When I used this condition

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

...the Str() function didn't work here. What difference did it make? thanks in advance :))

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.