S3 Tech Blog: ASP.NET Tip: Creating a Form Using PlaceHolder Controls

This example has a table called Parameters that has the following fields to help you determine how to build the table:

Field
Description

pkParameterID
Primary key

Prompt
Text to display next to control

DataType
Text field with the value 'String' or 'TF' in it (This will let you determine which control to show.)

You also could add extra fields indicating whether the field was required, a minimum/maximum length, and so forth, but this example is designed to show just the use of the PlaceHolder control.

You then can create a simple form like this one:

<%@ Page Language="C#" AutoEventWireup="true"
                       CodeFile="test.aspx.cs" Inherits="test" %>
<!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:Repeater ID="rptFields" runat="server">
         <HeaderTemplate>
         <table>
         </HeaderTemplate>
         <ItemTemplate>
            <tr>
               <td><%# Eval("Prompt") %>:</td>
               <td><asp:PlaceHolder ID="plControl" runat="server" />
               <input type="hidden" id="hdnFieldID"
                  runat="server"
                  value='<%# Eval("pkParameterID") %>' /></td>
            </tr>
         </ItemTemplate>
         <FooterTemplate>
         </table>
         </FooterTemplate>
      </asp:Repeater>
      <p align="center"><asp:LinkButton ID="btnSubmit"
         runat="server">Submit Data</asp:LinkButton></p>
   </div>
   </form>
</body>
</html>

The code behind for this page looks like this:

public partial class test : System.Web.UI.Page
{
   protected override void OnInit(EventArgs e)
   {
      base.OnInit(e);
      rptFields.ItemDataBound +=
         new RepeaterItemEventHandler(rptFields_ItemDataBound);
   }

   protected void Page_Load(object sender, EventArgs e)
   {
      Database db = new Database("(local)", "test", "sa", "dev1227");
      AddControls(db);
      db.Close();
   }

   private void AddControls(Database db)
   {
      DataTable dt = db.GetDataTableAdhoc("SELECT * FROM Parameters
                                           ORDER BY pkParameterID");
      rptFields.DataSource = dt;
      rptFields.DataBind();
   }

   void rptFields_ItemDataBound(object sender, RepeaterItemEventArgs e)
   {
      if (e.Item.ItemType != ListItemType.Item && e.Item.ItemType
          != ListItemType.AlternatingItem)
         return;

      DataRow dr = ((DataRowView)e.Item.DataItem).Row;
      PlaceHolder pl = (PlaceHolder)e.Item.FindControl("plControl");
      switch (dr["DataType"].ToString().ToLower())
      {
         case "string":
            TextBox txt = new TextBox();
            txt.ID = "txtField" + dr["pkParameterID"].ToString();
            pl.Controls.Add(txt);
            break;

         case "tf":
            CheckBox chk = new CheckBox();
            chk.ID = "chkField" + dr["pkParameterID"].ToString();
            pl.Controls.Add(chk);
            break;
      }
   }
}