In VB.NET, a function is a separate group of codes used to perform a specific task when the defined function is called in a program.
You can define a Function procedure only at the module level. Therefore, the declaration context for a function must be a class, a structure, a module, or an interface and can't be a source file, a namespace, a procedure, or a block.
Function procedure is public, but you can adjust their access modifiers' access levels.Function procedure can declare the data type of the value that the procedure returns.The following code defines a function called Add, which takes two parameters and returns the sum.
Public Module Functions
Function Add(num1 As Integer, num2 As Integer) As Integer
Return num1 + num2
End Function
End Class
To return a value from a function, you can either include it in a Return statement or assign the value to the function name.
The following example shows two different functions, one function returns a value using the return statement while the other function assigns the value to the function name and then uses the Exit Function statement to return.
Public Module Functions
Function Add(num1 As Integer, num2 As Integer) As Integer
Return num1 + num2
End Function
Function Subtract(num1 As Integer, num2 As Integer) As Integer
Subtract = num1 - num2
Exit Function
End Function
End Module
The Return statement simultaneously assigns the return value and exits the function.
Exit Function and Return statements cause an immediate exit from a Function procedure.Exit Function and Return statements can appear anywhere in the procedure, and you can mix Exit Function and Return statements.Exit Function without assigning a value to name, the procedure returns the default value for the data type that is specified in the return type.Object.A Sub procedure is a group of codes enclosed by the Sub and End Sub statements. The Sub procedure performs a task and then returns control to the calling code, but it does not return a value to the calling code.
Sub statement and ending with the first End Sub, Exit Sub, or Return statement encountered.Public, and you can call it from anywhere in your application that has access to the module, class, or structure in which you defined it.The following example uses the Sub statement to define the name, parameters, and code that form the body of a Sub procedure.
Public Module Subs
Sub CalculateArea(length As Double, width As Double)
Dim area As Double
If length = 0 Or width = 0 Then
' If either argument = 0 then exit Sub immediately.
Exit Sub
End If
area = length * width
' Print area to Immediate window.
Console.WriteLine(area)
End Sub
End Module
You can call a Function or Sub procedure by using the procedure name, followed by the argument list in parentheses, in an expression.
The following code calls the above-defined functions and sub from the Main method.
Imports System
Module Program
Sub Main()
Dim val1 = Functions.Add(3, 4)
Dim val2 = Functions.Subtract(3, 4)
Subs.CalculateArea(8, 5)
End Sub
End Module
When a Sub procedure returns to the calling code, execution continues with the statement after the statement that called it.
You can also call a function by using the Call keyword. In that case, the return value is ignored. Use of the Call keyword isn't recommended in most cases.