Textbox values disappear on postback - asp.net

Question

I have an asp.net page with a button that adds an additional row to a gridview for input to the database. The gridview consists of 3 textboxes(template fields), when I add a row the information already entered somehow disappears on the postback. I want the button to add additional rows without disspelling the data in the other rows, until I hit the submit button. Here's my code
Private Sub AddNewRowToGrid()
Dim rowIndex As Integer = 0
If ViewState("CurrentTable") IsNot Nothing Then
Dim dtCurrentTable As DataTable = DirectCast(ViewState("CurrentTable"), DataTable)
Dim drCurrentRow As DataRow = Nothing
If dtCurrentTable.Rows.Count > 0 Then
For i As Integer = 1 To dtCurrentTable.Rows.Count
'extract the TextBox values
Dim box1 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(1).FindControl("txtAdjAppr"), TextBox)
Dim box2 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(2).FindControl("txtAdjAmt"), TextBox)
Dim box3 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(3).FindControl("txtCmmts"), TextBox)
drCurrentRow = dtCurrentTable.NewRow()
drCurrentRow("Approval Date") = box1.ToString
dtCurrentTable.Rows(i - 1)("Total Amount") = box2.ToString
dtCurrentTable.Rows(i - 1)("Comments") = box3.ToString
'dtCurrentTable.Rows(i - 1)("Initials") =
rowIndex += 1
Next
dtCurrentTable.Rows.Add(drCurrentRow)
ViewState("CurrentTable") = dtCurrentTable
gvOLIAdj.DataSource = dtCurrentTable
gvOLIAdj.DataBind()
End If
Else
Response.Write("ViewState is null")
End If
'Set Previous Data on Postbacks
'SetPreviousData()
End Sub
Private Sub SetPreviousData()
Dim rowIndex As Integer = 0
If ViewState("CurrentTable") IsNot Nothing Then
Dim dats As DataTable = DirectCast(ViewState("CurrentTable"), DataTable)
If dats.Rows.Count > 0 Then
For i As Integer = 0 To dats.Rows.Count - 1
Dim box1 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(1).FindControl("txtAdjAppr"), TextBox)
Dim box2 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(2).FindControl("txtAdjAmt"), TextBox)
Dim box3 As TextBox = DirectCast(gvOLIAdj.Rows(rowIndex).Cells(3).FindControl("txtCmmts"), TextBox)
box1.Text = dats.Rows(i)("Approval Date").ToString()
box2.Text = dats.Rows(i)("Total Amount").ToString()
box3.Text = dats.Rows(i)("Comments").ToString()
rowIndex += 1
Next
End If
End If
End Sub

Answer 1

I can think of two reasons why this may be happening:
When you create controls dynamically it is VERY difficult to
retrieve the values in the code behind after postback
Your controls have the read-only attribute set in the raw HTML
You may want to try old-fashioned methods such as Request.Form http://msdn.microsoft.com/en-us/library/ms525985%28v=vs.90%29.aspx