Difference Between ByVal And ByRef

• ByVal passes a copy of the variable, changes made within the function do not affect the original variable.
• ByRef passes a reference to the variable, changes made within the function affect the original variable.

Choosing between ByVal and ByRef depends on whether you want the called function to have the ability to modify the original variable or not.

Sub Main()
Dim message As String = “Hello”
AppendExclamationByVal(message)
Console.WriteLine(message) ‘ Output: Hello
End Sub

Sub AppendExclamationByVal(ByVal str As String)
str = str & “!”
End Sub

Sub Main()
Dim message As String = “Hello”
AppendExclamationByRef(message)
Console.WriteLine(message) ‘ Output: Hello!
End Sub

Sub AppendExclamationByRef(ByRef str As String)
str = str & “!”
End Sub