Patrick Desjardins Patrick Desjardins - 1 month ago 13
ASP.NET (C#) Question

ASP.NET Custom user control to add dynamically

I have hard time to modify a page that had a Custom User Control directly to the ASPX page and now require to have it dynamically loaded when needed only. The User Control does have html and other controls via the ASCX file and has code in the code-behind.

I have read multiple page and have found that I cannot instantiate directly the User Control but should use the

Page.LoadControl(...)
. The problem is not the compiling but when the page load the control it happen that all controls inside the ASCX are null and then crash.

How can I use a User Control that has code in the ASCX and in the code-behind dynamically?

Edit:



Example of what I am doing in (PageLoad or PagePreRender or PagePreInit)

Control c = LoadControl(typeof(MyControl), null);
myControl= (MyControl)c;
myControl.ID = "123";
myControl.Visible = false;
Controls.Add(myControl);


MyControl does have for example
<div id="whatever" runat="server">
... and inside the MyControl it set the visibility to True or False... but when it does that, now it crash because the "whatever" div is NULL.

Answer

What I have done is use the Page.LoadControl method in the Page_Init to add the custom user control to a place holder on the page.

 protected void Page_Init(object sender, EventArgs e)
{

      //MyControl is the Custom User Control with a code behind file
      MyControl myControl = (MyControl)Page.LoadControl("~/MyControl.ascx");

      //UserControlHolder is a place holder on the aspx page where I want to load the
      //user control to.
      UserControlHolder.Controls.Add(myControl);

}

This works fine for me.

Here is the code for the dynamically loaded user control:

MyControl.ascx.cs

public partial class MyControl : System.Web.UI.UserControl
    {
        protected void Page_Init(object sender, EventArgs e)
        {
            LiteralControl lit = new LiteralControl("Test Literal Control");
            Page.Controls.Add(lit);
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            whatever.Visible = true;

            if (IsPostBack)
            {
                whatever.Visible = false;
            }

        }
    }
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