Cells.Controls

[rn5a]

This is the code of a DataGrid:

<asp:DataGrid ID="dgCart" OnEditCommand=" EditCart"
OnCancelCommand ="CancelUpda te" OnDeleteCommand ="DeleteFromCar t"
OnItemCommand=" ButtonClicked" OnPreRender="Ch angeWidth"
OnUpdateCommand ="UpdateCart " AutoGenerateCol umns="false"
runat="server">

<Columns>

<asp:TemplateCo lumn HeaderText="S.N .">
<ItemTemplate >
<asp:Label ID="lblSNo" Text='<%# Container.ItemI ndex + 1 %>'
runat="server"/>.
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn HeaderText="ID" >
<ItemTemplate >
<asp:Label ID="lblPID" Text='<%# Container.DataI tem("ProductID" ) %>'
runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn HeaderText="NAM E">
<ItemTemplate >
<asp:Label ID="lblPName" Text='<%# Container.DataI tem("ProductNam e")
%>' runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn HeaderText="DES CRIPTION">
<ItemTemplate >
<asp:Label ID="lblDescript ion" Text='<%#
Container.DataI tem("ProductDes cription") %>' runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:TemplateCo lumn HeaderText="PRI CE">
<ItemTemplate >
<asp:Label ID="lblPrice" Text='<%# Container.DataI tem("UnitPrice" ) %>'
runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:BoundColum n DataField="Quan tity" HeaderText="QTY ."/>

<asp:TemplateCo lumn HeaderText="SUB-TOTAL">
<ItemTemplate >
<asp:Label ID="lblSubTotal " Text='<%# Container.DataI tem("Total") %>'
runat="server"/>
</ItemTemplate>
</asp:TemplateCol umn>

<asp:EditComman dColumn EditText="EDIT" CancelText="CAN CEL"
HeaderText="EDI T" UpdateText="UPD ATE"/>

<asp:ButtonColu mn CommandName="de lete" HeaderText="DEL ETE"
Text="DELETE"/>

</Columns>

</asp:DataGrid>

Note that only the *QTY* column is a BoundColumn. Hence when a user
clicks *EDIT*, this column becomes editable i.e. it changes to a
TextBox.

This is the UpdateCommand event function named *UpdateCart*

Sub UpdateCart(obj As Object, ea As DataGridCommand EventArgs)
..........
..........
dgCart.DataBind ()

Response.Write( "Text: " & CType(ea.Item.C ells(5).Control s(0),
TextBox).Text & "<br>")
Response.Write( "Val: " & CType(ea.Item.C ells(0).Control s(0),
Label).Text)
End Sub

The first Response.Write line outputs the correct text. So for e.g.
when in the editable mode, if a user enters 10 in the TextBox of the
BoundColumn, the first Response.Write correctly outputs 10.

Using the second Response.Write line, I want to retrieve the text of
the row under the *S.N.* column that was just updated but it generates
the following error:

Unable to cast object of type 'System.Web.UI. LiteralControl' to type
'System.Web.UI. WebControls.Lab el'.

If I am not mistaken, ASP.NET adds a LiteralControl on either side of
a Label control. In other words, a Label control is always sandwiched
between 2 LiteralControls . Please correct me if I am wrong. & I guess
that's the reason why the above error gets thrown but if I change the
index of the Cells in the second Response.Write line from 0 to 1 or 2
or 3 or 4 to retrieve the *ID*, *NAME*, *DESCRIPTION* & *PRICE*
respectively, then ASP.NET still generates the above error!

Now why changing the Cells index in the second Response.Write line
from 0 to 1 or 2 or 3 or 4 generating the same error?

I know I can use FindControl instead of using the Cells & Controls
index but I would like to know what's causing the above error when the
Cells index is changed from 0 to 1 or 2 or 3 or 4.