Using C#/ASP.net how to Change Datagrid column

I am curious about what some of the properties are of the Datagrid. Most of what I read on the datagrid properties is a lot of double talk.
DataGrid1.Items[x]-->represents of a single row?
DataGrid1.Items.cells[x]-->represents a single cell?
DataGrid1.Items.cells[x].Controls--> represents ???? I have no idea. It is an array?

I get an error on ->Image img
c:\inetpub\wwwroot\SurplusInventory\DisplaySelectList.aspx.cs(153): 'Image' is an ambiguous reference

Thanks Tim

1. DataGrid1.Items[x]-->represents of a single row?

yes, or more correctly, a DataGridItem: http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.datagriditem.aspx


2. DataGrid1.Items.cells[x]-->represents a single cell?

yep.


3. DataGrid1.Items.cells[x].Controls--> represents ???? I have no idea. It is an array?

technically, it's a control collection: http://msdn2.microsoft.com/en-us/library/system.web.ui.control.controls.aspx.  You can access it in a similar fashion, however:  DataGrid1.Items[x].Cells[x].Controls[x].  Sometimes finding controls in the datagrid can be a little difficult, but you can always iterate when need be.


4. I get an error on ->Image img
c:\inetpub\wwwroot\SurplusInventory\DisplaySelectList.aspx.cs(153): 'Image' is an ambiguous reference

...sounds like you have another type of Image class declared somewhere, and the compiler doesn't know which type of "Image" the one in question is referring to.  Try using a complete declaration: 'System.Web.UI.WebControls.Image img'.  Also, make sure that you haven't declared the wrong image class somewhere in your code (such as System.Drawing.Image).  If you've created your own image class, you might want to think about renaming it.

wil

My code:
protected void DataGrid1_PreRender(object sender, EventArgs e)
        {
            foreach (DataGridItem itm in ProductDataGrid.Items)
            {
              System.Web.UI.WebControls.Image img = (System.Web.UI.WebControls.Image)itm.Cells[8].Controls[1];
              //  if (img.ImageUrl == null)
              //  {
                   // itm.Cells[8].Controls.Clear();
                 
                    //itm.Cells[8].Controls.Clear();
               // }
            }
        }

The Image img problem is fixed,but i get this error when the page is loading

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace:


[ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index]
   System.Web.UI.ControlCollection.get_Item(Int32 index) +2057582
   SurplusInventory.DisplaySelectList.DataGrid1_PreRender(Object sender, EventArgs e) +148
   System.Web.UI.Control.OnPreRender(EventArgs e) +2066972
   System.Web.UI.WebControls.BaseDataList.OnPreRender(EventArgs e) +21
   System.Web.UI.Control.PreRenderRecursiveInternal() +77
   System.Web.UI.Control.PreRenderRecursiveInternal() +161
   System.Web.UI.Control.PreRenderRecursiveInternal() +161
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360

 
Also, in your Image img = (Image)itm.Cells[cell number that holds the image control].Controls[1];  //gets the control in the specified cell
how do you know you want [1] for Controls[1]?

thanks
  tim

well, the error looks like you're asking for a control that isn't there; my guess would be that you're forgetting that indexing starts at 0, not 1, and although there may be 8 columns in the datagrid, the 8th cell is actually at index 7 (not 8):

System.Web.UI.WebControls.Image img = (System.Web.UI.WebControls.Image)itm.Cells[7].Controls[1];

...just a guess of course.  You can find exactly what's happening by placing a breakpoint on the prerender method and stepping through it, if you haven't already.

as for knowing the correct index of controls within cells, any cell that has only one server-side control in it will be at index 1; index 0 is given to the html (in the form of a literalcontrol) prior to the webcontrol in the cell.  Luckily, if you're not sure where the controls lie in the cell, you can always iterate them and simply count the iterations to learn their indexes:

//iterating the first cell in the first row in the datagrid
//set a breakpoint here so you can watch the iteration
foreach (Control ctl in DataGrid1.Items(0).Cells(0).Controls)
{
     //do something here that allows you to see the controls as you debug.
     string sCtlClientId = ctl.ClientId;
}

Scott Mitchell has an article here that can help, too.  Although it deals with template columns, the fundamentals are the same:  http://datawebcontrols.com/faqs/ProgrammaticAccess/AccessingTemplateColumnContents.print.shtml

let me know if you still need help with the error after reading this.
wil

No, i think my index is ok. My datagrid has like 14 columns. About half are visible. TemplateColumn is what i am trying to update with the prerender
my grid:

<asp:DataGrid id="ProductDataGrid" OnPreRender="DataGrid1_PreRender" OnPageIndexChanged="PageChangeClicked" OnItemCommand="DetailsClicked" OnSortCommand="SortEventHandler" style="Z-INDEX: 101; LEFT: 27px; POSITION: absolute; TOP: 66px" runat="server" Width="963px" AllowSorting="True" AllowPaging="True" AutoGenerateColumns="False" Font-Names="Arial Unicode MS" PageSize="15" CellPadding="1" BorderColor="Black" CellSpacing="1">
                <AlternatingItemStyle BackColor="#ccff66"></AlternatingItemStyle>
                <Columns>
                    <asp:BoundColumn DataField="product_id" SortExpression="product_id DESC" HeaderText="Product ID" ItemStyle-Height="10px" HeaderStyle-Height="10px">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="line" Visible="False" HeaderText="Line">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="category" SortExpression="category DESC" HeaderText="Category" ItemStyle-Wrap="False">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="sub_category" SortExpression="sub_category DESC" HeaderText="Sub-Category">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="manufacturer" SortExpression="manufacturer DESC" HeaderText="Manufacturer">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="alt_code" Visible="False" HeaderText="Alt Code">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="description" HeaderText="Description">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="list_price" SortExpression="list_price DESC" HeaderText="List Price" DataFormatString="{0:N}">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Right" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="sale_price" SortExpression="sale_price DESC" HeaderText="Sale Price" DataFormatString="{0:N}">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Right" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="posted_date" Visible="False" HeaderText="Posted Date">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="comments" HeaderText="Comments">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="picture_path" Visible="False" HeaderText="Picture Path">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle Wrap="False"></ItemStyle>
                    </asp:BoundColumn>
                    <asp:BoundColumn DataField="qty" Visible="False" HeaderText="Qty">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                    </asp:BoundColumn>
                    <asp:TemplateColumn HeaderText="Photo" ItemStyle-HorizontalAlign="Center" ItemStyle-VerticalAlign="Middle">
                        <ItemTemplate>
                            <img id="CameraImg" src='images/<%# DataBinder.Eval(Container.DataItem,"picture_path","TSCameraSmall.PNG") %>' alt="N/A" />
                        </ItemTemplate>
                    </asp:TemplateColumn>
                    <asp:ButtonColumn Text="Details" ButtonType="PushButton" HeaderText="Product Details" CommandName="Details">
                        <HeaderStyle Font-Size="Medium" Font-Underline="True" Font-Names="Book Antiqua" Wrap="False" HorizontalAlign="Center" VerticalAlign="Middle"></HeaderStyle>
                        <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle"></ItemStyle>
                    </asp:ButtonColumn>
                </Columns>
                <PagerStyle NextPageText="  Next --&gt;" PrevPageText="&lt;-- Prev.  " HorizontalAlign="Center"></PagerStyle>
            </asp:DataGrid>

thanks
  tim

ahhhh....i see what's happening now.

1. whether columns are visible or not, you still have to count them; the databound column at index 8 doesn't have any controls in it, so naturally an error will occur when you try to access a control that isn't there.  The image control is at index 13 (column 14).

2. html image controls and server-side asp image controls are accessed differently.  The asp image control (<asp:image>) will show up in the datagrid as a System.Web.UI.WebControls.Image, but an html image control (<img/>) is a System.Web.UI.LiteralControl...and in this specific case, since the image is databound, it is a System.Web.UI.DataBoundLiteralControl.  So, with that in mind, you'll have to access it at ProductDataGrid.Items[x].Cells[13].Controls[0], rather than at .Controls[1] (since it isn't a server-side control).

hope that clears it up : )
wil

protected void DataGrid1_PreRender(object sender, EventArgs e)
        {
            foreach (DataGridItem itm in ProductDataGrid.Items)
            {
              System.Web.UI.WebControls.Image img = (System.Web.UI.WebControls.Image)itm.Cells[13].Controls[1];
               if (img.ImageUrl == "")
               {  
                 itm.Cells[13].Controls.Clear();
               }
            }
        }

Thanks your code worked. I had to change 'img.ImageUrl == null' to 'img.ImageUrl == ""'. Not sure why in my database the value is <null> if there is no path set. One last thing when I clear() or use visible prop. I lose my grid border if the cell is cleared. Is there away around this or can I set the border back programmatical?

  Thanks Tim