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How can I access web controls from a code-behind page?

In the general declaration for your code behind class, create a control variable with the same name as the id of the control in your .aspx file:

Public Class CodeBehind : Inherits Page

Public ItemsGrid As DataGrid

Protected Sub Page_Load(ByVal Sender As System.Object, ByVal e As System.EventArgs)
If Not IsPostback Then
ItemsGrid.DataSource = GetMyDataSource()

ItemsGrid.DataBind()
End If
End Sub

End Class