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ASP.net GridView InvalidOperationException on foreach when deleting

I'm using ASP.net and i've added a delete button on a gridview and im trying to remove the row of the button clicked. The thing is though, that i get an InvalidOperationException on my foreach.
I may have other errors in the code or my logic may be wrong so if you see any of it please point them out. Thanks.
gridView cart.ASPX:
<asp:GridView ID="CartGrid" runat="server" AutoGenerateColumns="false" OnRowDeleting="RemoveSelected">
<Columns>
<asp:BoundField DataField="product_name" HeaderText="Name" />
<asp:BoundField DataField="price_per_unit" HeaderText="Price" />
<asp:BoundField DataField="unit" HeaderText="Unit" />
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="delSelected" runat="server" Text="Delete" CommandName="Delete"></asp:LinkButton>
</ItemTemplate>
<ItemStyle Width="100px" />
</asp:TemplateField>
</Columns>
</asp:GridView>
delete method cart.ASPX.CS
protected void RemoveBtn(object sender, GridViewDeleteEventArgs e)
{
ArrayList cartList = (ArrayList)Session["cartList"];
GridViewRow row = (GridViewRow)CartGrid.Rows[e.RowIndex];
String name = row.Cells[0].Text;
//String name = (string)CartGrid.DataKeys[e.RowIndex].Value;
//String name = CartGrid.SelectedRow.Cells[1].Text;
foreach (product p in cartList)
{
if (p.product_name.Equals(name))
{
cartList.Remove(p);
}
}
CartGrid.DataBind();
}

Hi I think the issue is that you are using the cartlist for loop and at the same time you want to delete values from the same which is not possible .
just you need to change your approach like create the empty list and add all the index into it from where you have to delete the value Staring from bottom to top like from end of list so that it can not effect the index of the list by deleted value and after loop you can delete it using the new empty list which contain the list of all the values which should be deleted.

You can't modify the collection you're iterating over with the foreach - please see this question for more information.

Retrieve values from GridView by changing a value in a DropDownList

I'm having problems retrieving the current row by changing the status of a DropDownList in the row. My code for the GridView is:
<asp:GridView ID="grdMappingList" runat="server" OnPageIndexChanging="grdMappingList_PageIndexChanging" AutoGenerateColumns="false" AllowPaging="true" PageSize="10" ShowHeaderWhenEmpty="true" UseAccessibleHeader="true" CssClass="table table-hover table-striped segment_list_tbl" >
<PagerStyle CssClass="grid_pagination" HorizontalAlign="Right" VerticalAlign="Middle" BackColor="#DFDFDF" />
<Columns>
<asp:BoundField HeaderText="Mapping Id" DataField="MAPPING_ID"></asp:BoundField>
<asp:BoundField HeaderText="PDM Name" DataField="PDM_NAME"></asp:BoundField>
<asp:BoundField HeaderText="PDM EntityID" DataField="PDM_ENTITY_ID" Visible="false"></asp:BoundField>
<asp:TemplateField HeaderText="Mapping Status" HeaderStyle-CssClass="width_120 aligned_center" ItemStyle-CssClass="width_120 aligned_center" Visible="true">
<ItemTemplate>
<asp:DropDownList id="ddlMappingStatus" runat="server" SelectedValue='<%# Bind("MappingCompleted") %>' OnSelectedIndexChanged="ddlMappingStatus_SelectedIndexChanged" AutoPostBack="true">
<asp:ListItem Text="Done" Value="DONE"></asp:ListItem>
<asp:ListItem Text="Not Done" Value="NOT DONE"></asp:ListItem>
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
And the code behind is:
protected void ddlMappingStatus_SelectedIndexChanged(object sender, EventArgs e)
{
int MappingID = Convert.ToInt16(grdMappingList.SelectedRow.Cells[0].Text);
DropDownList ddgvOpp = (DropDownList)grdMappingList.SelectedRow.FindControl("ddlMappingStatus");
if (ddgvOpp.Equals("DONE"))
{
}
}
I am getting an error on this line:
DropDownList ddgvOpp (DropDownList)grdMappingList.SelectedRow.FindControl("ddlMappingStatus");
and this line:
int MappingID = Convert.ToInt16(grdMappingList.SelectedRow.Cells[0].Text);
It seems that I can't retrieve the values! I dont know why. When I choose a new status from the DropDownList, I want to get all the values of the row in order to update the record.

Unfortunately, SelectedRow does not mean what you think it means. It doesn't just simply mean the current row you are working on or the current row with the controls that you are using. That property must get set somehow. This is usually done through a "Select" button on the GridView, such as an <asp:ButtonField> with the command name "Select".
You really do not need this however. You just need the row you are working with. Since you are using the SelectedIndexChanged event of your DropDownList, you already have what you need. You just need to go about it a different way.
First, get the DropDownList. Then get the row of the DropDownList. Now do whatever you need with the row.
But, from your code, it looks like you may not even need the row. You just need the value of the DropDownList. So you could skip that all together. But if you do need the row, here is how you would do that too.
protected void ddlMappingStatus_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList ddlMappingStatus = (DropDownList)sender;
if(ddlMappingStatus.SelectedItem.Text.ToUpper() == "DONE")
{
}
GridViewRow row = (GridViewRow)ddlMappingStatus.NamingContainer;
}
Now when you use <asp:BoundField> controls in your GridView, getting their values isn't very clean. You are forced to hardcode the column index like you were doing:
GridViewRow row = (GridViewRow)ddlMappingStatus.NamingContainer;
String mappingID = row.Cells[0].Text;
I tend to prefer using <asp:TemplateField> controls so I can use FindControl() to get what I am after. This prevents any reordering of the columns from breaking the code, as you'd have to hardcode different indexes. So for example, to find that DropDownList (since it already is a <asp:TemplateField>), you'd do something like this:
DropDownList ddlMappingStatus = (DropDownList)row.FindControl("ddlMappingStatus");

Gridview column linkbutton change the value according to data

I am trying to complete a simple task;
a gridview column gets an integer data if integer is equals to zero print "active" and set the commandname of the linkbutton to active else set linkbutton text and command value to inactive.
here is what I have so far
<Columns>
<asp:BoundField HeaderText = "User Name" DataField="UserName"
HeaderStyle-Width="16%" ItemStyle-HorizontalAlign="Center" />
<asp:BoundField HeaderText = "Role" DataField="RoleNAME"
HeaderStyle-Width="14%" ItemStyle-HorizontalAlign="Center" />
<asp:BoundField HeaderText = "Group" DataField="GroupName"
HeaderStyle-Width="12%" ItemStyle-HorizontalAlign="Center" />
<asp:ButtonField ButtonType="link" CommandName = "Active"
HeaderText="Status" Text="Active"
HeaderStyle-Width="10%" ItemStyle-HorizontalAlign="Center" />
<asp:ButtonField ButtonType="link" CommandName = "Edit"
HeaderText="" Text="Edit/View"
HeaderStyle-Width="10%" ItemStyle-HorizontalAlign="Center" />
</Columns>
codebehind
protected void grdMyQueue_RowdataBound(object sender, GridViewRowEventArgs e)
{
// In template column,
if (e.Row.RowType == DataControlRowType.DataRow)
{
var obj = (User)e.Row.DataItem;
if (obj.isDisabled == 0)
{
LinkButton linkButton = new LinkButton();
linkButton.Text = "Active";
linkButton.Enabled = true;
linkButton.CommandName = "Active";
//linkButton.CommandArgument = e.Row. //this might be causing the problem
e.Row.Cells[3].Controls.Clear();
e.Row.Cells[3].Controls.Add(linkButton);
}
else
{
LinkButton linkButton = new LinkButton();
linkButton.Text = "InActive";
linkButton.Enabled = true;
linkButton.CommandName = "InActive";
e.Row.Cells[3].Controls.Add(linkButton);
}
}
}
However when I Click the active linkbutton on the cell I get an error at onrowcommand function
protected void OnRowCommand(object sender, GridViewCommandEventArgs e)
{
int index = Convert.ToInt32(e.CommandArgument); // this is the error line
GridViewRow gvRow = userManager.Rows[index];
TableCell usrName = gvRow.Cells[0];
string userName = usrName.Text;
....
How can I manage to change LinkButton text and CommandName depending on that integer data?
P.S I tried Eval but I couldnt figure out whats going on....

I would simply return the data from your data source, as intended. Then I would use an Update Panel to avoid the Postback that will occur from your Link Button. As for the text modifying I would use Javascript, so Javascript will read the page on the client. So when your data source returns:
One
One
Two
One
The Javascript can analyze those rows, then modify the internal cell within the Grid quite painless.
An example of Javascript:
$(".Activator").each(function () {
if ($(this).prev().find(':checkbox').prop('checked')) {
$(this).text("Deactivate");
}
});
This example will validate if a checkbox is checked, if it is modify the internal text to the class .Activator.
Then the internal item in the Grid for code on front-end would look like:
<asp:TemplateField HeaderText="Active">
<ItemTemplate>
<asp:CheckBox
ID="CustomerCheck" runat="server"
Checked='<%# Eval("Active") %>'
Enabled="false" />
<asp:LinkButton
ID="lbCustomerActive" runat="server"
Text="Activate"
CommandName="OnActivate"
ToolTip='<%# "Activate or Deactivate Course: " + Eval("CourseID") %>'
OnClick="CustomerCheck_Click"
CssClass="Activator">
</asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
As you can see, as the internal data is changed the Javascript will automatically adjust the value for me every time the Data Source is binded again. Which the CustomerCheck_Click would execute the code on the server, which will read the Command Argument which contains the Row Id. Which will Update that particular record without a problem and rebind the Grid. (Partially lied, I'm parsing the Tooltip).
You would instantiate on server side like:
((LinkButton)sender).ToolTip;

Retriving cell value from gridview rowcommand

hey I'm using to buttons in a gridview each which I want to assign to specific action involves retrieving certain cell values from the gridview columns
I tried using
GridViewRow row = (GridViewRow (((Button)e.CommandSource).NamingContainer);
but it gives me Unable to cast object of type 'System.Web.UI.WebControls.GridView' to type 'System.Web.UI.WebControls.Button'.
I also tried
int index = Convert.ToInt32(e.CommandArgument);
GridViewRow row = GridView1.Rows[index];
it gives me the following error
Specified argument was out of the range of valid values.
Parameter name: index
note that when I tried to specify the commandParameters property of the ButtonField the compiler said that it's not a valid parameter for the ButtomField
and I have 8 columns in the gridview so its not out of range
or alternatively could I use more than one select command button
if so how to say which one is clicked??
please help me im desperate
ASP code:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="AcitivityId" DataSourceID="SqlDataSource1" Height="304px" Width="912px" OnRowCommand="GridView1_RowCommand">
<Columns>
<asp:BoundField DataField="AcitivityId" HeaderText="AcitivityId" InsertVisible="False" ReadOnly="True" SortExpression="AcitivityId" />
<asp:BoundField DataField="ActiviityName" HeaderText="ActiviityName" SortExpression="ActiviityName" />
<asp:BoundField DataField="ActivityLocation" HeaderText="ActivityLocation" SortExpression="ActivityLocation" />
<asp:BoundField DataField="ActivityStartDate" HeaderText="ActivityStartDate" SortExpression="ActivityStartDate" />
<asp:BoundField DataField="ActivityDueDate" HeaderText="ActivityDueDate" SortExpression="ActivityDueDate" />
<asp:BoundField DataField="ActivityDescription" HeaderText="ActivityDescription" SortExpression="ActivityDescription" />
<asp:ButtonField ButtonType="Button" CommandName="Avaliable" Text="Show avaliable buses" />
<asp:ButtonField ButtonType="Button" CommandName="Assigned" Text="Show assigned buses "/>
</Columns>
</asp:GridView>

I use this code in a number of places on my site to get the row from an object triggering a GridViewRowCommand
protected void btnUpdate_Command(object sender, CommandEventArgs e)
{
GridViewRow g = (GridViewRow)((Button)sender).NamingContainer;
// other stuff
}
Hope this helps.

How do I edit data being bound to a datagrid?

In reference to Link loaded into my gridview try to navigate to my local server. The columns I have in the datagrid are Customer #, Description, Link.
I've got a function set up that's called on rowDataBound, but how do I retrieve what link is in the row so that I can edit it, and then rebind it to the datagrid?
protected void grdLinks_RowDataBound( object sender, GridViewRowEventArgs e )
{
if ( e.Row.RowIndex == 2 )
{
}
}
And here is my gridview code
<asp:GridView ID="grdLinks" runat="server" AutoGenerateColumns="False" DataSourceID="ldsCustomerLinks"
OnRowDataBound="grdLinks_RowDataBound" EmptyDataText="No data was returned."
DataKeyNames="ID" OnRowDeleted="grdLinks_RowDeleted" Width="80%" BackColor="White"
HorizontalAlign="Center" BorderColor="#999999" BorderStyle="None" BorderWidth="1px"
CellPadding="3" GridLines="Vertical">
<RowStyle BackColor="#EEEEEE" ForeColor="Black" />
<Columns>
<asp:BoundField DataField="CustomerNumber" HeaderText="Customer Number" SortExpression="CustomerNumber" />
<asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" />
<asp:HyperLinkField DataTextField="Link" HeaderText="Link" SortExpression="Link" DataNavigateUrlFields="Link" Target="_blank" />
</Columns>
</asp:GridView>
<asp:LinqDataSource ID="ldsCustomerLinks" runat="server" ContextTypeName="ComplianceDataContext"
TableName="CustomerLinks" EnableDelete="true">
</asp:LinqDataSource>

If I'm understanding you correctly, you want to get the value of a data item called Link. If so, then something like this should work:
EDIT: I think what you're saying is that you want to grab the value Link from the database, manipulate it and then set the Url of the HyperLink to the new, manipulated value, if so then it would look like this:
ASPX Page (Updated to reflect posted code)
<Columns>
<asp:BoundField DataField="CustomerNumber" HeaderText="Customer Number" SortExpression="CustomerNumber" />
<asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" />
<asp:TemplateField HeaderText="Link">
<ItemTemplate>
<asp:HyperLink ID="hlParent" runat="server" Text='<% #(Eval("Link")) %>' />
</ItemTemplate>
</asp:TemplateField>
</Columns>
I modified the ASP from your original question by adding an ID and removing the reference to the NavigateUrl attribute from the HyperLink control.
Code
protected void grdLinks_RowDataBound( object sender, GridViewRowEventArgs e )
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
string link = DataBinder.Eval(e.Row.DataItem, "Link") as string;
if (link != null && link.Length > 0)
{
// "FindControl" borrowed directly from DOK
HyperLink hlParent = (HyperLink)e.Row.FindControl("hlParent");
if (hlParent != null)
{
// Do some manipulation of the link value
string newLink = "https://" + link
// Set the Url of the HyperLink
hlParent.NavigateUrl = newLink;
}
}
}
}

RowDataBound is called for every row in the GridView, including headers, footers, etc. Therefore, you should start by examining only the rows containing data.
Once you're on a row, there are several ways to examine the cells. One is just to use the cell index (2 here). That seems simple in your situation, but will lead to frustration if you ever rearrange the columns.
Here's an example of that from MSDN:
void CustomersGridView_RowDataBound(Object sender, GridViewRowEventArgs e)
{
if(e.Row.RowType == DataControlRowType.DataRow)
{
// Display the company name in italics.
e.Row.Cells[1].Text = "<i>" + e.Row.Cells[1].Text + "</i>";
}
A better way is to use FindControl with the item's ID.
protected void gvBarcode_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
HyperLink hlParent = (HyperLink)e.Row.FindControl("hlParent");
}
}

You may also want to look into letting the gridview do it for you.
You can use the datanavigateurlformatstring property to insert querystring parameters if that's what you are trying to do.
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.hyperlinkfield.datanavigateurlformatstring.aspx