loop of buttons ASP.NET

Question

I've been stuck for the last two hours and need help. I've tried every single example I could find online and none of them work. I'm building a web page in ASP.NET and want to make a list of buttons. Doesn't seem too hard right? It's been causing me issues though.

This is my code:

<ul>
  <form id="tagloop" runat="server">
    <% foreach (string i in data)%>
      <%Response.Write("<li><button runat=\"server\" type=\"submit\" onserverclick=\"ClickTag\">" + i + "</button></li>");%>
  </form>
</ul>

If I remove the Response.Write() it only loops once but the one button it does generate actually works and calls the method on click. Also, the variable i doesn't apply.

<ul>
  <form id="tagloop" runat="server">
    <% foreach (string i in data)%>
      <li><button runat="server" type="submit" onserverclick="ClickTag"> i </button></li>
  </form>
</ul>

Is there anyway I can get it to loop, have the text of i in data, and also call the correct function on click? I haven't been able to find a balance of all three yet and any help will be appreciated.

What's your preferred solution. Do you want server side controls with code behind event handlers? — Marco, Jun 08 '18 at 18:43
It possibly loops once because you have only 1 object in data? — Aman, Jun 08 '18 at 18:46

Marco · Accepted Answer · 2018-06-08T20:05:17.743

If you want to create server side controls, you're better off using an asp:Repeater:

<asp:Repeater runat="server" ID="Repeater1" OnItemCommand="Repeater1_ItemCommand">
    <ItemTemplate>
        <li>
            <asp:Button runat="server"  ID="RepeaterButton" Text="<%# Container.DataItem %>" OnClick="RepeaterButton_Click"/>
        </li>
    </ItemTemplate>
</asp:Repeater>

protected void Page_Load(object sender, EventArgs e)
{    
    if(IsPostBack) return;
    var data = new List<string> { "Test1", "Test2", "Test3", "Test4" };
    Repeater1.DataSource = data;

    Repeater1.DataBind();
}

You have to write a bit more code, but you avoid adding to much logic into your markup and do not have to use Response.Write, which is prone to errors and typos.

You can even do this with strongly typed objects! Let's assume you have a person class:

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

And you have a method in your .cs file that returns a list of Persons:

IEnumerable<Person> Persons()
{
    for (int i = 0; i < 10; i++)
    {
        yield return new Person { FirstName = $"Foo{i}", LastName = $"Bar{i}" };
    }
}

You can then reference your object properties in your repeater control:

<asp:Repeater runat="server" ID="Repeater1" ItemType="WebFormsSandbox.Person">
    <ItemTemplate>
        <li>
            <asp:Button runat="server"  ID="RepeaterButton" Text="<%#: Item.FirstName %>  <%#: Item.LastName %>" OnClick="RepeaterButton_Click"/>

        </li>
    </ItemTemplate>
</asp:Repeater>

Reference: https://msdn.microsoft.com/en-us/library/x8f2zez5(v=vs.100).aspx

I'm getting an invalid postback or callback error. I've tried changing multiple things to nothing different. Any ideas? — Jeff Rohlman, Jun 08 '18 at 19:37
https://stackoverflow.com/questions/293699/invalid-postback-or-callback-argument-with-databound-controls See my updated code for the Page_Load method. You need to add a postback check — Marco, Jun 08 '18 at 20:00

score 0 · Answer 2 · answered Jun 08 '18 at 18:51

Something like this?

    <form id="tagloop" runat="server">
        <%
            List<int> data = new List<int>();
            data.Add(1);
            data.Add(2); %>
        <% foreach (int i in data)%>
           <%Response.Write("<li><button runat=\"server\" 
           type=\"submit\"onclick=\"ClickTag\">" + i + "</button></li>");%>
    </form>

loop of buttons ASP.NET

2 Answers2