All controls are null within usercontrol

If the user control is in your current project, then you need to include the src in the register statement:

<%@ Register TagPrefix="uc1" TagName="NavTop" Src="controls/NavTop.ascx" %>

However, if you use this user control in more than one page, then you can also register it in web.config:

<system.web>  <pages>    <controls>      <add tagPrefix="uc1" tagName="NavTop" src="~/controls/NavTop.ascx" />    </controls>  </pages></system.web>

One other thing to be aware of: there are times when the visual studio designer does not "see" your changes to controls on the page if you only make the changes in source view. If you change a control name, for example, you could end up with a control with the new name in the ascx but a reference to a control with the old name in the designer file. At runtime, this will result in the designer file property being null.

After having been burnt by this a number of times, if I make any changes in source view, I either check to see that the designer file has been updated correctly or I switch to design view, make a minor change, then save the page/user control.

I had this problem when I was adding a user control in the code behind the wrong way. You have to use the Page.LoadControl method to initialize the control you can't just use new.

        //WRONG        UserControls.BingoCardPage bcp = new UserControls.BingoCardPage();        form1.Controls.Add(bcp);        //RIGHT        UserControls.BingoCardPage bcp = (UserControls.BingoCardPage)Page.LoadControl("~/UserControls/BingoCardPage.ascx");        form1.Controls.Add(bcp);

The issue here is usually due the the load mechanics of user controls, they load after the page typically. So as a result the controls have not yet been initialized on your usercontrol (causing the null ref) during the containing page_load method. One way to work around this is to just create and set a property on the usercontrol and have the usercontrol wire-up/populate its own UI in its Page_Load method.

Something like this:

//Pageprotected void Page_Load(object sender, EventArgs e){    test.Text = "Hello World!";}//User Controlpublic string Text {get; set;}protected void Page_Load(object sender, EventArgs e){    lblTest.Text = Text;}