Windows Forms and Controls

Using code we can create a second instance of the original form and display it so without further ado lets do so. Replace the MsgBox code in the cbAccept button’s click event with the following:

       Dim newForm As frmMain = New frmMain()
       Dim newTxt As TextBox = New TextBox()
       newTxt.Location = New System.Drawing.Point(80, 80)
       newTxt.Width = 100
       newTxt.Text = "New TextBox"
       newForm.Controls.Add(newTxt)
       newForm.BackColor = System.Drawing.Color.Brown
       newForm.cbAccept.Visible = False
       newForm.lblEnterText.Left -= 15
       newForm.lblEnterText.Width -= 30
       newForm.txtEnteredText.Left -= 30
       newForm.txtEnteredText.Text = "New Instance of original form"
       newForm.txtEnteredText.Width = "New Instance of original form".Length * 6
       newForm.Show()

O.k. I’ve created a new instance of frmMain, created a brand new control and added it to our new instance and then changed a few control properties. Note the Point which is part of the System.Drawing namespace. This namespace is used to draw almost everything on the interface. Also pay close attention to the method used to add a control to a form. In this case I created a reference to a TextBox, set some properties and used the Controls.Add method to add it to the form. Then I changed some properties of the new instance of the form, backcolor, made the Accept Button invisible and changed the position and width of the label and existing textbox. This, I did using the new -= capabilities of VB.Net which saves me having to write the property out twice. Finally I used the .Length property of a string to set the width of the existing textbox. The Len function can still be used as far as I know but since everything in .Net is now an object, including variables and in this case an undeclared string, all now have methods and properties.

This is but a brief demonstration of the power of inheritance with forms. You can go further, create a class that inherits your base form class, add new controls and add new events and so on. For now though I’m going to finish with an examination of the code for everything we have done.