ASP.NET Change Dropdown Control ID Inside Repeater Item Dynamically

StackOverflow https://stackoverflow.com/questions/9153248

  •  23-04-2021
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Pregunta

Can someone tell me how I can get this to work. I want to distinguish dropdown controls inside a repeater control. I understand now about the lifecyle and how the buffer is already writen, but what are my alternatives? Here is what happens

Code File

    Dim repeatTimes((TotalAdInsured - 1)) As Integer

    myRepeater.DataSource = repeatTimes
    myRepeater.DataBind()

Aspfile

<asp:Repeater ID="myRepeater" runat="server">
    <ItemTemplate>
         <asp:DropDownList ID="AdTitle<%# Container.ItemIndex %>" runat="server">
             <asp:ListItem Selected="True" Value="" Text=""/>
             <asp:ListItem Selected="False" Value="Miss" Text="Miss"/>
             <asp:ListItem Selected="False" Value="Ms" Text="Ms"/>
             <asp:ListItem Selected="False" Value="Mrs" Text="Mrs"/>
             <asp:ListItem Selected="False" Value="Mr" Text="Mr"/>
             <asp:ListItem Selected="False" Value="Other" Text="Other"/>
         </asp:DropDownList>
    </ItemTemplate>
</asp:Repeater>

Returns this error

Parser Error Message: 'AdTitle<%# Container.ItemIndex %>' is not a valid identifier.

¿Fue útil?

Solución

I want to distinguish dropdown controls inside a repeater control.

You don't need to. Here's some sample code that might help you out:

Markup:

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label runat="server" ID="lblMsg" Text="Click a button" />
        <hr />
        <asp:Repeater runat="server" ID="rptAwesome" onitemcommand="rptAwesome_ItemCommand"
            >
            <ItemTemplate>
                <asp:Button runat="server" ID="btnAwesome"
                    Text='<%# "Button #" + Container.ItemIndex %>'
                    CommandArgument='<%# Container.DataItem %>'/><br />
            </ItemTemplate>
        </asp:Repeater>
    </div>
    </form>
</body>
</html>

Codebehind:

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            var x = new int[] { 1, 2, 3, 4, 5 };
            rptAwesome.DataSource = x;
            rptAwesome.DataBind();
        }
    }
    protected void rptAwesome_ItemCommand(object source, RepeaterCommandEventArgs e)
    {
        Button btnAwesome = (Button)e.CommandSource;
        lblMsg.Text = string.Format("btnAwesome.ID = {0}, e.CommandArgument = {1}", btnAwesome.ID, e.CommandArgument);
    }
}

Otros consejos

You cannot create a Unique ID inside a repeater through the markup like that. You can however retrieve the dropdown in the codebehind by using FindControl on the Repeater.

Dim adTitle As DropDownList = MyRepeater.FindControl("AdTitle")
If (Not adTitle Is Nothing) Then
  ''Do something here
End If

Ok... in a nutshell you can't do what you're trying to do in the manner you are currently doing it.

The ID property of a control can only be set using the ID attribute in the tag and a simple value. Example: <asp:Button runat="server" id="Button1" />

I can see what your trying to do, but I don't really understand Why...

A repeater control will contain 1 item, per item in your datasource, so it's perfectly fine to just call your DropDownList ID="AdTitle" as that will be a different 'AdTitle' from the one in the next row.

To get them back server side, you would just iterate through the Items in your Repeater & FindControl("AdTitle") to get the specific DropDownList for that item.

If it's absolutely necessary to have the IDs incrementing, you'll need to do this programmatically (probably on the ItemDataBound event to create a DropDownList and add it to your ItemTemplate.

Expanding on BC's answer: I recently had the same issue, albeit with a checkbox, I needed to set the ID as I used that when persisting choices. A bit clunky but I did it when on Item Data Bound.

Here's the markup:

<asp:Repeater ID="Repeater1" runat="server" >
<HeaderTemplate>Header<br /><br /></HeaderTemplate>
<ItemTemplate>
    <asp:CheckBox ID="cb" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Name") %>' />
     ...other controls removed for brevity
</ItemTemplate>
<FooterTemplate>
    <asp:Button ID="Button1" runat="server" OnClick="Submit" Text="Submit" />
</FooterTemplate>
</asp:Repeater>

I set up and bound a collection of this class

public class mst
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Number { get; set; }
    public bool NumberRequired { get; set; }
}

Do the necessary in Page_Load

        Repeater1.ItemDataBound += new RepeaterItemEventHandler(Repeater1_ItemDataBound);
        Repeater1.DataSource = listOfMsts;
        Repeater1.DataBind();

Followed by, this where I set ID:

    void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
        {
            var mst = (mst)e.Item.DataItem;
            ((CheckBox)e.Item.FindControl("cb")).ID = mst.Id.ToString();
        }
    }

So when the submit button is hit I can loop thru and grab the Id of those checked and save:

  protected void Submit(object sender, EventArgs e)
    {
    foreach (var item in Repeater1.Items)
        {
            var checkboxes = ((RepeaterItem)item).Controls.OfType<CheckBox>().ToList();
            if (checkboxes[0].Checked)
            {
                Save(checkboxes[0].ID);
                ....other stuff
            }
        }
    }

You could add an event handler to Repeater.ItemDataBound and create the control within the handler using the reference to the item container.

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