I'm working on a .NET WebForm app which has a master page. The .NET can not recognize many elements in the aspx file. For example it say Label is not a valid asp element and then says most likely reason is a malformed web.config file.

I double check my web.config and all looks good. The other webpages do not have same issue. The interesting thing is I do not have this issue inside the MasterPage.

I also tried recreate the page from scratch but still having same issue.

I'm using VS2019. Framework 4.6

CodePudding user response：

You have to provide some sample code and markup. Also, if you have a master page, then that is a huge deal also. As a general rule, asp.net controls you drop on the page are able to be used from code behind. However, the code for the standard page(s) that we use as a "child" of a master pages means that code behind for the master page can easy use controls in master page. And code behind for the page being displayed in that master page ALSO can freely use its own controls. But controls between the master page and the working child page is VERY different matter.

And of course controls dropped into a repeater, or say listview (or even gridview) means that the one label or text box control is automatic repeated over and over. As such, you have to pull/get/use the one row out of that data bound repeating control, and then from that one repeating row grab the control in question.

So, saying I can't start my car, or I can't use or get a control?

We need more information as to the context of what control, where it is (in the master or child), and is the control perhaps nested inside of a data bound repeater, listview, gridview etc.

so, edit your question - add some details as to the markup, where it is (master or the child page), and we can help.

So, as a general rule, code behind in master page is free to use controls in the master page.

And in the web page you created, once again code behind is free to use controls in that page.

It can be more difficult to say have code in master page, and have it reference controls in the child page that is being displayed. But, then again, it is VERY rare that code in master page would need to reference or play with controls in the child page, since a master page will (usually) just be your main navigation bar - and it will be the same for many if not all pages you display - hence you master page really can't know what controls will exist in the current child page being displayed.