Dynamically Loading Multiple ASCX Pages in an ASPX Page using Switch-Case

In ASP.NET Web Forms, you often have pages that need to display different user controls ( .ascx ) dynamically based on some condition (like a menu selection or query string parameter). Instead of creating separate pages for each control, you can load them dynamically at runtime using LoadControl and a switch-case structure.

Scenario

Suppose you have multiple user controls:

Dashboard.ascx
NewClient.ascx
AddNewClient.ascx
masterList.ascx
…and many others

You want to load these controls into a placeholder ( ControlHolder ) in your Default.aspx page based on a numeric or string parameter.

Implementation Steps

1. Add a Placeholder in ASPX Page

In your ASPX page ( Default.aspx ), add a PlaceHolder control where dynamic controls will be loaded:

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

This placeholder acts as a container for your user controls.

2. Load Controls Dynamically in Code-Behind

In your code-behind ( Default.aspx.cs ), you can use a switch-case statement to determine which .ascx control to load:

  
    protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        string pageID = Request.QueryString["PageID"] != null ? Request.QueryString["PageID"].ToString() : ""; // Example: get value from URL ?PageID=1
        LoadUserControl(pageID);
    }
}

private void LoadUserControl(string pageID)
{
    switch (pageID)
    {
        case "1":
            Dashboard dashboared_ctrl = (Dashboard)LoadControl("Dashboard.ascx");
            ControlHolder.Controls.Add(dashboared_ctrl);
            break;

        case "2":
            NewClientmaster newclient_ctrl = (NewClientmaster)LoadControl("NewClient.ascx");
            ControlHolder.Controls.Add(newclient_ctrl);
            break;

        case "3":
            AddNewClientList addnewclient = (AddNewClientList)LoadControl("AddNewClient.ascx");
            ControlHolder.Controls.Add(addnewclient);
            break;

        case "4":
            UCCmasterList uccmaster_ctrl = (UCCmasterList)LoadControl("masterList.ascx");
            ControlHolder.Controls.Add(uccmaster_ctrl);
            break;

        case "5":
            AddClientList addclient_ctrl = (AddClientList)LoadControl("AddClientList.ascx");
            ControlHolder.Controls.Add(addclient_ctrl);
            break;

        case "6":
            ViewIPOMaster viewipo_master = (ViewIPOMaster)LoadControl("ViewMaster.ascx");
            ControlHolder.Controls.Add(viewipo_master);
            break;

        case "7":
            AddIPOMaster addipomastr = (AddIPOMaster)LoadControl("AddMaster.ascx");
            ControlHolder.Controls.Add(addipomastr);
            break;

        case "8":
            AddIPO addipo = (AddIPO)LoadControl("AddIPO.ascx");
            ControlHolder.Controls.Add(addipo);
            break;

        case "9":
            UpdateExchangeIPO updateEx = (UpdateExchangeIPO)LoadControl("Update.ascx");
            ControlHolder.Controls.Add(updateEx);
            break;

        case "10":
            OrderList orderlist_ctrl = (OrderList)LoadControl("OrderList.ascx");
            ControlHolder.Controls.Add(orderlist_ctrl);
            break;

        case "11":
            UPIReport upireport_ctrl = (UPIReport)LoadControl("Report.ascx");
            ControlHolder.Controls.Add(upireport_ctrl);
            break;

        case "12":
            IPOSettingsOffline offlinesetting_ctrl = (IPOSettingsOffline)LoadControl("Settings.ascx");
            ControlHolder.Controls.Add(offlinesetting_ctrl);
            break;

        case "13":
            OfflineOrders offlinelist_ctrl = (OfflineOrders)LoadControl("Orders.ascx");
            ControlHolder.Controls.Add(offlinelist_ctrl);
            break;

        case "14":
            IPOAllotment ipoallotment_ctrl = (IPOAllotment)LoadControl("Allotment.ascx");
            ControlHolder.Controls.Add(ipoallotment_ctrl);
            break;

        case "15":
            ExchangePage ExchangePage_ctrl = (ExchangePage)LoadControl("ExchangePage.ascx");
            ControlHolder.Controls.Add(ExchangePage_ctrl);
            break;

        case "16":
            ViewIssue ViewIssue_ctrl = (ViewIssue)LoadControl("ViewIssue.ascx");
            ControlHolder.Controls.Add(ViewIssue_ctrl);
            break;

        case "17":
            ViewIPO ViewIPO_ctrl = (ViewIPO)LoadControl("ViewIPO.ascx");
            ControlHolder.Controls.Add(ViewIPO_ctrl);
            break;

        default:
            // Optionally show a default control or message
            ControlHolder.Controls.Add(new LiteralControl("<p>Select a valid option</p>"));
            break;
    }
}

3. How It Works

Get the Page Identifier: You can use QueryString , a DropDownList , or any parameter to determine which control to load.
Switch-Case Logic: Each case corresponds to a specific .ascx control. The control is loaded dynamically and added to the placeholder.
Type Casting: (Dashboard)LoadControl("Dashboard.ascx") casts the loaded control to the correct class so you can access its public properties or methods.
Adding to Placeholder: ControlHolder.Controls.Add(dashboared_ctrl) adds the control to the page dynamically at runtime.

4. Advantages of this Approach

Single ASPX page for multiple views: Reduces code duplication.
Dynamic content loading: Only loads the control needed based on user interaction.
Maintainability: Adding new controls is simple — just add a new case in the switch.
Encapsulation: Each user control handles its own UI and logic.

5. Optional Enhancements

Use QueryString or Session for persistence.
Default control: Show a welcome dashboard if no PageID is provided.
Error handling: Wrap LoadControl in try-catch to prevent runtime errors.
Refactor using Dictionary : For large numbers of controls, you can use a dictionary mapping instead of long switch-case.

Example URL to Load Controls

  
    Default.aspx?PageID=1   -> Loads Dashboard.ascx
Default.aspx?PageID=2   -> Loads NewClientmaster.ascx
Default.aspx?PageID=10  -> Loads OrderList.ascx

Conclusion

Using switch-case with LoadControl in ASP.NET Web Forms is an efficient way to dynamically load multiple user controls into a single ASPX page, making your application modular and maintainable.