Question

I have a simple asp.net user control:

<%@ Control Language="C#" AutoEventWireup="true" 
    CodeBehind="QueryDefinitionItem.ascx.cs"
    Inherits="xxx.UserControls.QueryDefinitionItem" %>
    <link href="../Styles/Site.css" rel="stylesheet" type="text/css" />
    <div class="title">
      <h1 id="TextField" runat="server"></h1>
    </div>

Code behind:

 public partial class QueryDefinitionItem : System.Web.UI.UserControl
{
    private string m_text;
    protected void Page_Load(object sender, EventArgs e)
    {
        TextField.InnerText = m_text;
    }

    public void SetText(string text)
    {
        m_text = text;
    }
}

I use LoadControl to load one instance programatically:

protected void Page_Load(object sender, EventArgs e)
    {
        var control = (QueryDefinitionItem)LoadControl(typeof (QueryDefinitionItem),null);
        control.SetText("test2");
        itemsPanel.Controls.Add(control);}

I then use the SetText function to set the text and once the Page Load is fired I get a NullReferenceException that says TextField is null…

I cant figure out why.

Answer 1

You should have to use LoadControl(string) method instead of LoadControl(Type,Param) and store value directly to the HtmlControl. (There is bug take a look at connect).

protected void Page_Load(object sender, EventArgs e)
{
}
public void SetText(string text)
{
  TextField.InnerText = text;
}

Or create a property,

   public string Text
    {
      get { return TextField.InnerText; }
      set { TextField.InnerText=value;  }
    }

Use Page_Init or Page_Load event to create controls dynamically.

protected void Page_Load(object sender, EventArgs e)
  {
  var control = (QueryDefinitionItem)LoadControl("~/QueryDefinitionItem.ascx");
  control.SetText("test2");
  itemsPanel.Controls.Add(control);
  }