A Web page defines an IsPostBack property. You can poll the IsPostBack property to determine whether the page is being rendered as the result of a request or a user postback. For example, when we click the paging links for a DataGrid control, we are posting the page back, but the event handler is binding the DataGrid control. Hence we don't need to bind the DataGrid control in the Page_Load event a second time. You can use the IsPostBack property to eliminate the extra call to DataBind . Listing 16.14 demonstrates a Page_Load event that checks the IsPostBack property.
Listing 16.14 Using IsPostBack to Eliminate Extra Calls to DataBind
Private Sub Page_Load(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles MyBase.Load If (Not IsPostBack) Then DataGrid1.DataSource = New Contact() DataGrid1.DataBind() End If End Sub