Event Handling means performing  some actions by using events. By using Event Handling, we can perform Validations in windows application which is a built in feature in the web application.For Web applications, we have several controls which are used to perform validations. But there are no controls in windows applications. By using this Event Handling Mechanism, we can achieve validations in Windows Application also.There are two Types of Events as follows.

The Events which are raised due to Mouse are called as Mouse Events.The following table shows you Some of the Mouse Events.

Take an Example. We have to create a Registration Form.We have to implement the following conditions that mean validations. Follow the below steps to know how to perform Event Handling.

• Open Visual Studio 2013. Go to File  and then New, and then Project. Then a new window will be open. Select Visual Basic, Windows Application and also give the Name for your project and click on Ok.
• Then, the new Windows Application will be created.
• Now design the form as shown in the below figure.

Change the properties of the every control in the above diagram as shown in the below table.

Control	Property
Textbox1	Id as  txtName
Textbox2	Id as  txtMobile
Textbox3	Id as  txtEmail
Textbox4	Id as txtCity
Label1	Id as  lblName Text as Name
Label2	Id as  lblMobile Text as Mobile No
Label3	Id as  lblEmail Text as Email Id
Label4	Id as lblCity Text as City
Button	Id as btnSubmit Text as Submit

Write the following code. [vbnet] Public Class Form1 Private Sub txtName_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtName.KeyPress If Not (Asc(e.KeyChar) = 8) Then If Not ((Asc(e.KeyChar) >= 97 And Asc(e.KeyChar) <= 122) Or (Asc(e.KeyChar) >= 65 And Asc(e.KeyChar) <= 90)) Then e.KeyChar = ChrW(0) MessageBox.Show("Enter only characters") e.Handled = True End If End If End Sub Private Sub txtMobile_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtMobile.KeyPress If Asc(e.KeyChar) <> 13 AndAlso Asc(e.KeyChar) <> 8 AndAlso Not IsNumeric(e.KeyChar) Then MessageBox.Show("Please enter numbers only") e.Handled = True End If End Sub Private Sub btnSubmit_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click MessageBox.Show("Successfully submitted") End Sub Private Sub txtCity_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtCity.KeyPress If Not (Asc(e.KeyChar) = 8) Then If Not ((Asc(e.KeyChar) >= 97 And Asc(e.KeyChar) <= 122) Or (Asc(e.KeyChar) >= 65 And Asc(e.KeyChar) <= 90)) Then e.KeyChar = ChrW(0) MessageBox.Show("Enter only characters") e.Handled = True End If End If End Sub End Class [/vbnet] Output: If you are trying to enter any number in Name or City filed. Then, you will get the following error. If you are trying to enter any character in Mobile No filed. Then, you will get the following error.

If you enter all the fields successfully. Then you will get the following message.

• Before developing an application like forms, then  developer need to have an knowledge regarding toolbox.
• Validation and logic of an object gives a good effect.
• More errors will give more knowledge while debugging.