从文件后面的代码向ASP.NET C＃中的Listview控件动态添加子控件

Question

This is my code behind the file:

ImageButton img = new ImageButton();
img.AlternateText = "<%# Eval(\"colA\") %>";
img.ImageUrl = "~/img.png";
img.ID = "img";
ListView3.Controls.Add(img);
ListView3.DataSource = ds; //DataSet containing column - colA with 20 rows
ListView3.DataBind();

I am basically trying to add control, which will be generated after some processing, to listview control; but it keeps giving me error at

ListView3.DataBind();

An exception of type 'System.InvalidOperationException' occurred in System.Web.Extensions.dll but was not handled in user code Additional information: An item placeholder must be specified on ListView 'ListView3'. Specify an item placeholder by setting a control's ID property to "itemPlaceholder". The item placeholder control must also specify runat="server".

And this is my ListView3 code:

<asp:ListView ID="ListView3" runat="server">
    <LayoutTemplate>
        <table id="itemPlaceholderContainer" runat="server">
            <tr id="itemPlaceholder" runat="server"></tr>
        </table>
    </LayoutTemplate>
    <ItemTemplate>

    </ItemTemplate>
</asp:ListView>

I have tried group template and placeholder control. But I think I might have made a mistake in placeholder. Please figure this error for me! Thanks in advance.

Answer 1

You could place the image directly inside the ItemTemplate

<ItemTemplate>
    <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="~/img.png" AlternateText='<%# Eval("colA") %>' />
</ItemTemplate>

But to solve your error. A ListView repeats items, you when you want to add Controls to it you have to specify an index.

ListView3.Items[i].Controls.Add(img);