VB.NET Technology

A dynamic linking library (DLL) is linked to your program at run time. DLL is similar to an EXE but is not directly executable. Functions in the dll are called from the main exe. It provides a way to split what would be a very large exe into an exe plus one or more dlls.

Creating DLL in VB.Net

To creating DLL in VB.Net just follow next steps-

Goto File -> New Project then choose Class Library you will see window like below.

Here i am going to show DLL for addition, subtraction, multiplication, and division. Code for this is given below

Public Class Class1
    Public Function add(ByVal x As Integer, ByVal y As Integer) As Integer
        Dim z As Integer = x + y
        Return z
    End Function
    Public Function [sub](ByVal x As Integer, ByVal y As Integer) As Integer
        Dim z As Integer = x - y
        Return z
    End Function
    Public Function mul(ByVal x As Integer, ByVal y As Integer) As Integer
        Dim z As Integer = x * y
        Return z
    End Function
    Public Function div(ByVal x As Integer, ByVal y As Integer) As Integer
        Dim z As Integer = x \ y
        Return z
    End Function
End Class

After this Build this class by pressing F6 and dll will generate this class library now you can use this in any other application where you want to use this dll.

Using DLL in VB.Net Application

For using DLL in application you have to make add reference of the dll that you

Design the form as shown in below picture

Private Sub Button1_Click(ByVal sender As System.Object, 
	ByVal e As System.EventArgs) Handles Button1.Click
        Dim c1 As ClassLibrary1.Class1 = New Class1()
        Dim result As Integer = c1.add(Integer.Parse(textBox1.Text), Integer.Parse(textBox2.Text))
        textBox3.Text = result.ToString()
    End Sub
Private Sub Button2_Click(ByVal sender As System.Object, 
	ByVal e As System.EventArgs) Handles Button2.Click
        Dim c2 As ClassLibrary1.Class1 = New Class1()
        Dim result As Integer = c2.[sub](Integer.Parse(textBox1.Text), Integer.Parse(textBox2.Text))
        textBox3.Text = result.ToString()
    End Sub
Private Sub Button3_Click(ByVal sender As System.Object, 
	ByVal e As System.EventArgs) Handles Button3.Click
        Dim c3 As ClassLibrary1.Class1 = New Class1()
        Dim result As Integer = c3.mul(Integer.Parse(textBox1.Text), Integer.Parse(textBox2.Text))
        textBox3.Text = result.ToString()
    End Sub
Private Sub Button4_Click(ByVal sender As System.Object, 
	ByVal e As System.EventArgs) Handles Button4.Click
        Dim c4 As ClassLibrary1.Class1 = New Class1()
        Dim result As Integer = c4.div(Integer.Parse(textBox1.Text), Integer.Parse(textBox2.Text))
        textBox3.Text = result.ToString()
    End Sub