How to load c# ascx user control based on condition?

Question

I am converting an aspx website from separate aspx language pages (utilizing the same code behind) to one main aspx with user controls. I have one user control ascx file for each language, all with the same IDs in them so the same code behind can be used for any of them. How can I conditionalize which one gets displayed to the user without running into compile issues?

use session variable Session["lang"] This is what I have:

<%@ Register TagPrefix="section" TagName="account"      Src="account.ascx" %>
<%@ Register TagPrefix="section" TagName="account_span" Src="account_span.ascx" %>

EDIT: Solution This is what I ended up using in the .aspx

<asp:PlaceHolder ID="PlaceHolder_section" runat="server" />

and what I have in the code-behind: section variable hold each section name and suffix is the language

 PlaceHolder_section.Controls.Add(this.LoadControl(section + suffix + ".ascx"));

Can you share some code please? Can't you use localization to make language dependent pages? — Patrick Hofman
There is no need to use the word "this" on this.LoadControl.... — Marvin Zumbado

Markus Markus · Accepted Answer · 2014-01-24T15:08:52

You can use the LoadControl-method to load a UserControl dynamically. See this sample for details.
So in your case, you would have code like this in the CodeBehind (Page Init or Load) of your page:

MyUserControlType ctrl;
if (Session["lang"] == "en-US") 
    ctrl = (MyUserControl) LoadControl("~/PathToUserControl/eng.ascx");
else if (Session["lang"] == "es-ES")
    ctrl = (MyUserControl) LoadControl("~/PathToUserControl/span.ascx");
else 
    ctrl = null;
if (ctrl != null)
{
    // Initialize properties of ctrl
    Controls.Add(ctrl);
}

Instead of having a long list of ifs or a switch statement, you could name your UserControls after a certain pattern and store a suffix in the session:

string userCtrlSuffix = ((string) Session["UserControlSuffix"]) ?? "Eng";
MyUserControlType ctrl = (MyUserControl) LoadControl("~/PathToUserControl/UserControl" + userCtrlSuffix + ".ascx");
// Initialize properties of ctrl
Controls.Add(ctrl);

As @samy mentioned in the comments, loading controls dynamically needs to happen early in the page lifecycle in order to handle ViewState correctly and hook up event handlers properly.

How to load c# ascx user control based on condition?

1 Answers