Question

I’m adding a User Control for each record pulled up in a data reader, here’s the basic loop:

while (dr.Read()) {      ImageSelect imgSel = new ImageSelect(dr['Name'].ToString());      myPanel.Controls.Add(imgSel); } 

The problem is that there are no controls added to the page, I check the html output and there is my panel, with nothing in it.

I even stepped through the code in the debugger, and verified that myPanel.Controls gets a control added on each loop, with the count being 6, no errors, but then they dont show up on the page.

I’ve run the above code in the Page_Init and Page_Load events, both with the same result.

EDIT: Ok so I’ve switched to using LoadControl(‘….ascx’) to get my control instance, which is now working. But originally I was also passing in data via the controls constructor.. Is this still possible or do I just need to set them via get/sets?

EDIT 2: Thanks to Freddy for pointing out that the LoadControl has an overload where you CAN pass in constructor params, see accepted answer.

EDIT 3: After trying this method both with and without the constructor. I have found its better to just use setters for any properties I want the control to have versus trying to use the passed in object array for my constructor.

Answer 1

Update: As Steve pointed out, the overload of LoadControl that uses the type won’t take into account the controls in the ascx. This is also mentioned in this answer: Dynamically Loading a UserControl with LoadControl Method (Type, object[]).

As I mentioned before, the get/set are more in line with the asp.net model, so I recommend using that with the LoadControl variation that receives the user control path. That said, the Steve’s version is an interesting alternative: http://www.grumpydev.com/2009/01/05/passing-parameters-using-loadcontrol/.

My take is the LoadControl with type is meant to be used with web custom controls instead.

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If it is an user control you should use LoadControl(usercontrolpath) to get the instance of the user control.

You can use a constructor by doing:

var name = dr['Name'].ToString(); var imgSel = LoadControl(typeof(ImageSelect), new object[]{ name }); myPanel.Controls.Add(imgSel); 

Notice that depending on the project model you are using, you need to add a Reference to the aspx to use it with the typeof variation:

<%@ Reference Control='~/somepath/myusercontrol.ascx' %> 

Ps. I usually use the set/get for controls as I find them more in line with the asp.net model