Basicaly MDI means Multiple Document Interface,With the help of mdi form we can view and work with several documents at once ( see picture1.1) .NET provides great support for creating and working with MDI applications such as financial services organizations where the user needs to work with several documents at one time.
Picture 1.1
In .NET, we need only set the IsMdiContainer property of the form to True(see picture1.2). You create the child
forms at design time or at run time via code, and then set their MdiParent properties to reference a form whose
IsMdiContainer property is True. We can change a MDI parent/child relationship at run time. It also allows an
application to contain multiple MDI parent forms.
Picture1.2
Example
Add new form and set the property IsMdiContainer to true and add this code
Public Class Mdiparent
Dim i As Integer = 1
Private Sub mnuNewFrom_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles mnuNewFrom.Click
Me.IsMdiContainer = True
Dim MyChild As New System.Windows.Forms.Form()
MyChild.MdiParent = Me
MyChild.Show()
MyChild.Text = "MDI Child" & i
i = i + 1
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.Text = "MDIparent"
End Sub
End Class