--- VISTA DISEÑO -----

<asp:GridView runat="server" ID="GvVentas" DataKeyNames="ID" OnRowUpdating="GvVentas_RowUpdating"
            OnSelectedIndexChanging ="GvVentas_SelectedIndexChanging" OnRowEditing ="GvVentas_RowEditing" AutoGenerateColumns="False" OnRowCancelingEdit="GvVentas_RowCancelingEdit">
         
            <Columns>
                <asp:CommandField HeaderText="Edit-Update" ShowEditButton="True" />

            <asp:BoundField DataField="ID" HeaderText="ID" ReadOnly="true" />
              <asp:BoundField DataField="TIE" HeaderText="TIE" ReadOnly="true"/>
                <asp:BoundField DataField="CREDITO" HeaderText="CREDITO" ReadOnly="true" />
                  <asp:BoundField DataField="CONTADO" HeaderText="CONTADO" ReadOnly="true" />
                    <asp:BoundField DataField="TOTAL" HeaderText="TOTAL" ReadOnly="true" />
                     <asp:TemplateField HeaderText="FCH" SortExpression="FCH">
                <ItemTemplate>
                        <asp:Label ID="LBFch" runat="server" Text='<%# Bind("FCH") %>'></asp:Label>
                    </ItemTemplate>
                    <EditItemTemplate>
                        <asp:TextBox ID="TXTFch" runat="server" Text='<%# Bind("FCH") %>'></asp:TextBox>
                    </EditItemTemplate>
                </asp:TemplateField>
                      

            
            </Columns>
            <RowStyle BackColor="#E3EAEB" />          
        </asp:GridView>

--- CODIGO SERVIDOR----

Protected Sub GvVentas_RowUpdating(ByVal sender As Object, ByVal e As GridViewUpdateEventArgs)
        Using cn As New SqlConnection(ConfigurationManager.ConnectionStrings("CadSQL").ToString())
            Dim cmd As New SqlCommand()
            cmd.Connection = cn
            cmd.CommandText = "UPDATE VENTDA SET FCH = @FCH WHERE ID = @ID"
            cmd.CommandType = CommandType.Text
            Dim IDVentas As String = GvVentas.Rows(e.RowIndex).Cells(1).Text()
            Dim FCH As String = DirectCast(GvVentas.Rows(e.RowIndex).FindControl("TXTFch"), TextBox).Text
            cmd.Parameters.Add("@ID", SqlDbType.Int).Value = IDVentas
            cmd.Parameters.Add("@FCH", SqlDbType.Date).Value = FCH
            cn.Open()
            cmd.ExecuteNonQuery()
            cn.Close()
            cn.Dispose()
        End Using
        GvVentas.EditIndex = -1
        BindData("B")
    End Sub

Dim IDVentas As String = GvVentas.Rows(e.RowIndex).Cells(1).Text()
            Dim FCH As String = DirectCast(GvVentas.Rows(e.RowIndex).FindControl("TXTFch"), TextBox).Text

RowUpdating GridView

VB.NET