How to edit datatable rows in Gridview

Question

and thanks for viewing my post. I currently have a gridview populated by a datatable in viewstate. My touble is I am unable to edit the rows. I will show you the code below, but what happens when I click edit is the textbox in cell 2 becomes empty, but the text in cell 1 doesn't. Here is code I have so far starting with creating the data table:

GridView markup:

<asp:GridView ID="GridView2" runat="server" Visible="False" 
                    AutoGenerateColumns="false" ShowFooter="True" 
                    AutoGenerateDeleteButton="True" AutoGenerateEditButton="True">
                <Columns>

    <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />
    <asp:TemplateField HeaderText="Action Item">
        <ItemTemplate>
            <asp:TextBox ID="TextBox1" Width="500px" TextMode="MultiLine" runat="server"></asp:TextBox>

        </ItemTemplate>

        <FooterTemplate>
         <asp:Button ID="ButtonAdd" OnClick="ButtonAdd_Click" runat="server" Text="Add New Row" />
        </FooterTemplate>
        </asp:TemplateField>

    </Columns>
                </asp:GridView>

'set initial dt :
Private Sub SetInitialRow()
        Dim dt As New DataTable()
        Dim dr As DataRow = Nothing
        dt.Columns.Add(New DataColumn("RowNumber", GetType(String)))
        dt.Columns.Add(New DataColumn("Action Item", GetType(String)))
        dr = dt.NewRow()
        dr("RowNumber") = 1
        dr("Action Item") = String.Empty
        dt.Rows.Add(dr)
        'dr = dt.NewRow();

        'Store the DataTable in ViewState
        ViewState("CurrentTable") = dt

        GridView2.DataSource = dt
        GridView2.DataBind()

'Then I add a row with a button click in gridview footer:

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(GridView2.Rows(rowIndex).Cells(1).FindControl("TextBox1"), TextBox)

                    drCurrentRow = dtCurrentTable.NewRow()
                    drCurrentRow("RowNumber") = i + 1
                    drCurrentRow("Action Item") = box1.Text

                    rowIndex += 1
                Next
                'add new row to DataTable
                dtCurrentTable.Rows.Add(drCurrentRow)
                'Store the current data to ViewState
                ViewState("CurrentTable") = dtCurrentTable

                'Rebind the Grid with the current data
                GridView2.DataSource = dtCurrentTable
                GridView2.DataBind()
            End If
        Else
            Response.Write("ViewState is null")
        End If

        'Set Previous Data on Postbacks
        SetPreviousData()
    End Sub

Now here is where I have trouble. This code updates the row number (first column), but does nothing to the second column. It actually deletes the content.

Protected Sub GridView2_RowEditing(sender As Object, e As System.Web.UI.WebControls.GridViewEditEventArgs) Handles GridView2.RowEditing
        'Set the edit index.
        Dim dt As DataTable = CType(ViewState("CurrentTable"), DataTable)
        GridView2.EditIndex = e.NewEditIndex
        GridView2.DataSource = ViewState("CurrentTable")
        GridView2.DataBind()
    End Sub

Protected Sub GridView2_RowUpdating(sender As Object, e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles GridView2.RowUpdating

'Retrieve the table from the session object.
Dim dt As DataTable = CType(ViewState("CurrentTable"), DataTable)

'Update the values.
Dim row = GridView2.Rows(e.RowIndex)
dt.Rows(row.DataItemIndex)("RowNumber") = (CType((row.Cells(1).Controls(0)), TextBox)).Text
 dt.Rows(row.DataItemIndex)("Action Item") = (CType((row.Cells(2).FindControl("TextBox1")), TextBox).Text)

'Reset the edit index.
GridView2.EditIndex = -1

'Bind data to the GridView control.
GridView2.DataSource = ViewState("CurrentTable")
GridView2.DataBind()
End Sub

Could you please help me figure out where I'm going wrong? Thank you!

Josh

Answer 1

Here is the markup you need to create an EditItemTemplate within your TemplateField:

<asp:GridView ID="GridView2" runat="server" Visible="False" AutoGenerateColumns="false"
              ShowFooter="True" 
              AutoGenerateDeleteButton="True" AutoGenerateEditButton="True">
    <Columns>
        <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />
        <asp:TemplateField HeaderText="Action Item">
            <ItemTemplate>
                <asp:TextBox ID="TextBox1" Width="500px" TextMode="MultiLine" runat="server"></asp:TextBox>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox id="EditActionItemTextBox" runat="server" Width="500px" TextMode="MultiLine"></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:Button ID="ButtonAdd" OnClick="ButtonAdd_Click" runat="server" Text="Add New Row" />
            </FooterTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Now in your code-behind where you are updating your data table, do this:

'Update the values.
Dim row = GridView2.Rows(e.RowIndex)
dt.Rows(row.DataItemIndex)("RowNumber") = (CType((row.Cells(1).Controls(0)), TextBox)).Text
dt.Rows(row.DataItemIndex)("Action Item") = (CType((row.FindControl("EditActionItemTextBox")), TextBox).Text)

Note: In your <ItemTemplate> you may want to consider making the control read-only so that your users know they cannot change the value, usually when a user sees a text box they think they can edit the content, but it completely makes sense to have an editable text box in edit mode of your grid view. To change the the <ItemTemplate> text box to read-only, just add ReadOnly="True", like this:

<ItemTemplate>
    <asp:TextBox ID="TextBox1" Width="500px" TextMode="MultiLine" 
                 runat="server" ReadOnly="True"></asp:TextBox>
</ItemTemplate>

Depending upon the browser, the control will have a slight gray tinge to it. The user will be able to click on the text, but will not be able to change the text.