Dynamically loaded user control not rendering

Question

I'm trying to make a usercontrol work like a plugin: load it dynamically (using reflection) from a user's selection. After I click the button, I can see that the UI had adjusted to supposedly indicate that the user control has been loaded but I cannot the control itself. I even used viewstate but still I cannot see the control.

Please find my code below:

protected void Page_Load(object sender, EventArgs e)
    {
        //the scenario should be: a user clicking a button and from there, 
        //loads the control just below it, but still in the same page.
        if (Page.IsPostBack)
            LoadUserControl();

        //(a)I also tried to put in a ViewState but still nothing happens.
        //if (ViewState["UserControl"] != null)
        //{
        //    UserControl uc = (UserControl)ViewState["UserControl"];
        //    pnlReportControl.Controls.Add(LoadControl());
        //}

    }

//supposedly done after a button click
private void LoadUserControl()
    {
        enrolmentReports = string.Concat(Server.MapPath("~"), enrolmentDll);

        assembly = Assembly.LoadFrom(enrolmentReports);

        Type type = assembly.GetType("TZEnrollmentReports.EnrollmentUserControl");

        enrolmentMethodInfos = type.GetMethods();

        //also tried this way but also didn't work
        //Page.LoadControl(type, null);

        UserControl uc1 = (UserControl)LoadControl(type, null);

        pnlReportControl.Controls.Add(uc1);

        //(a)
        //ViewState["UserControl"] = uc1;
    }

Please help. This is just the first step of the whole complicated process. I still have to get a dataset from that report. But I think I'm leaving that to another thread.

Thank you!

If you try to debug you code, is `uc1` correctly instantiated? Is it the user control you expect to be shown? — themarcuz, May 16 '12 at 10:17
actually yes. when i try to debug the code, it shows the usercontrol that i expect and all the methods in it. the UI even changes to accommodate the supposed height of the user control. — iceheaven31, May 16 '12 at 10:22
are you sure the problem is not on the usercontrol itself? maybe it can't produce the html properly. Have you tried to load it on the page in the hardcoded way (so not dynimically loaded), to verify that it shows up correctly? — themarcuz, May 16 '12 at 10:29
i just created a new control and verified that it renders correctly when i tested.. but now it still not appearing, not even adjusting the UI like what it previously does.. — iceheaven31, May 18 '12 at 04:51
thank you very much. i should have really verified that the user control renders very well on its own before incorporating it dynamically. — iceheaven31, Jun 08 '12 at 10:08

score 1 · Answer 1 · edited May 23 '17 at 11:56

1

I believe that this is by design with the LoadControl(Type, Object) that it doesn't return what you are expecting.

If you change it to use LoadControl("PathOfControl") then this should work.

See this SO Q&A for more info Dynamically Loading a UserControl with LoadControl Method (Type, object[])

edited May 23 '17 at 11:56

Community

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1

answered May 18 '12 at 09:01

Tim B James

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score 1 · Answer 2 · answered May 18 '12 at 10:14

A suggestion that could help you solve this issue, is to change a little the approach. Usually developing a pluggable system, you base the pluggability to some interfaces. In your case, I would create an interface IPlugin that defines a method like CreateUI and some other to retrieve the data managed by the custom control internally, in some generic form.

This way, you'll delegate to the plugin implementation (your custom control) the responsability to create the UserControl properly and to return it to the caller (your page). Once loaded the plugin implementation via reflection (something like this):

Assembly pluginDLL = Assembly.Load(System.IO.File.ReadAllBytes(fullPath));
Type pluginType = pluginDLL.GetType(step.PluginClass);
IPlugin plugin = (IPlugin)Activator.CreateInstance(pluginType);

then you can load the Control on your page:

pnlReportControl.Controls.Add(plugin.CreateUI());

score -2 · Answer 3 · answered May 16 '12 at 10:10

-2

try replacing following code in your page_load method

if (Page.IsPostBack) LoadUserControl(); with if (!Page.IsPostBack) LoadUserControl();

answered May 16 '12 at 10:10

rt2800

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He talk about showing the control after a click on a button, so it's correct to evaluate `Page.IsPostBack`. Even if I hope it's just an oversimplified example, because I would do it in the click event handler... – themarcuz May 16 '12 at 10:19

Dynamically loaded user control not rendering

3 Answers3