Textbox in gridview

i was trying to add a textbox to a gridview so a user can enter some data. The problem is once the textbox is added to the gridview row i cant enter anything into it - in short it acts like a label:
    Private Function CreateTextbox(ByVal TextboxText As String, ByVal TextboxToolTip As String) As TextBox         Dim txtbox As TextBox = New TextBox         With txtbox             .Text = TextboxText             .ToolTip = TextboxToolTip & ...