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POAdding dynamic columns to an ASP.NET Gridview
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  1. POAdding dynamic columns to an ASP.NET Gridview
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    copied!<p>I'm having a problem dynamically adding columns to a GridView. I need to change the layout -- i.e. the included columns -- based on the value in a DropDownList. When the user changes the selection in this list, I need to remove all but the first column and dynamically add additional columns based on the selection.</p> <p>I have only one column defined in my markup -- column 0, a template column, in which I declare a Select link and another application specific LinkButton. That column needs to always be there. When the ListBoxSelection is made, I remove all but the first column and then re-add the desired columns (in this sample, I've simplified it to always add a "Title" column). Here is a portion of the code:</p> <pre><code>RemoveVariableColumnsFromGrid(); BoundField b = new BoundField(); b.DataField = "Title"; this.gvPrimaryListView.Columns.Add(b); this.gvPrimaryListView.DataBind(); private void RemoveVariableColumnsFromGrid() { int ColCount = this.gvPrimaryListView.Columns.Count; //Leave column 0 -- our select and view template column while (ColCount &gt; 1) { this.gvPrimaryListView.Columns.RemoveAt(ColCount - 1); --ColCount; } } </code></pre> <p>The first time this code runs through, I see both the static column and the dynamically added "Title" column. However, the next time a selection is made, the first column is generated empty (nothing in it). I see the title column, and I see the first column to its left -- but there's nothing generated within it. In the debugger, I can see that gvPrimaryListView does indeed still have two columns and the first one (index 0) is indeed a template column. In fact, the column even retains it's width which is set as 165px in the markup below (for debugging purposes).</p> <p>Any ideas?</p> <pre><code>&lt;asp:GridView ID="gvPrimaryListView" runat="server" Width="100%" AutoGenerateColumns="false" DataKeyNames="Document_ID" EnableViewState="true" DataSourceID="odsPrimaryDataSource" AllowPaging="true" AllowSorting="true" PageSize="10" OnPageIndexChanging="activeListView_PageIndexChanging" AutoGenerateSelectButton="False" OnSelectedIndexChanged="activeListView_SelectedIndexChanged" Visible="true" OnRowDataBound="CtlDocList_RowDataBound" Font-Size="8pt" Font-Names="Helvetica"&gt; &lt;Columns&gt; &lt;asp:TemplateField ShowHeader="false"&gt; &lt;ItemTemplate&gt; &lt;asp:LinkButton EnableTheming="false" ID="CtlSelectDocRowBtn" runat="server" Text="Select" CommandName="Select" CssClass="gridbutton" OnClick="RowSelectBtn_Click" /&gt; &lt;asp:ImageButton EnableTheming="false" ID="DocViewBtn" runat="server" ImageUrl="../../images/ViewDoc3.png" CssClass="gridbutton" CommandName="Select" OnClick="DocViewBtn_Click" /&gt; &lt;/ItemTemplate&gt; &lt;ItemStyle Width="165px" /&gt; &lt;/asp:TemplateField&gt; &lt;/Columns&gt; &lt;EmptyDataTemplate&gt; &lt;asp:Label ID="Label6" runat="server" Text="No rows found." SkinID="LabelHeader"&gt;&lt;/asp:Label&gt; &lt;/EmptyDataTemplate&gt; &lt;/asp:GridView&gt; </code></pre> <hr> <p>Just some additional information.</p> <p>It has nothing to do with the fact that it is the first column but everything to do with the fact that it is a TemplateField. If I put a normal column to the left (in the markup) and shift the TemplateField column to the right, the first column renders fine, and the (now second) TemplateField column disappears.</p> <p>Another strange thing -- the problem doesn't happen the first postback -- OR THE SECOND -- but it starts on the third postback and then continues for subsequent postbacks. I'm stumped.</p>
 

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