Element 'content' is not a known element. this can occur if there is a compilation error in the website, or the web.config file is missing.

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2010-11-03

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_{Wednesday, November 3, 2010 6:09 AM}

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

<asp:Content showed a green wavy line , and on hover displayed the above error.

Now I am having certain problems.

1. Visual Studio 2010 hangs when I try to use ToolBox.

2. Intellisense for asp.net controls is not working.

I have tried replacing web.config file (frm backup) , tried to debug - it doesnt show anything.

All other websites are working alright. Have problem with only one of the websites.

All replies (6)

_{Friday, November 5, 2010 6:25 AM ✅Answered}

OK i commented out this in my config file

Everythin seems to work fine now ....

But i really duno waz "jsonSerialization" for .... and wt will be the effects of it ...???

_{Wednesday, November 3, 2010 9:55 AM}

Please check the Masterpage and see that pages inherit ContentPlaceHolders properly.

_{Wednesday, November 3, 2010 3:10 PM}

Nuthin workin ....

I tried tried replacing web.config and master page with my backup files .. no luck .....

Can it be a problem with Visual Studio 2010?

Why does it hang? It should not hang if their is a compilation error ?

_{Thursday, November 4, 2010 2:12 PM}

hello,

I'm experiencing the same problem with UserControl.

I created two UserControl and put them in a contentpage:

GV_GP.ascx; GV_GC.ascx; Proprietari.aspx.cs .

Controls are properly registered

<%@ Register Src="../Controls/GV_GP.ascx" TagName="GV_GP" TagPrefix="uc1" %>
<%@ Register Src="../Controls/GV_GC.ascx" TagName="GV_GC" TagPrefix="uc2" %>

The problem is that the first one is properly recognized and working.
The second is not, and I have the same Warning telling that the element is not known.

I have to tell that at the beginning they were both fine. Later, without changing anything, this annoying problem came out.

I've compiled again and again and no other errors are found. All Settings seem to be fine (as I havent changed any).

Browsing here and there I found someone saying this solution should work:

As a workaround, you can try the following:

Close VS, delete schema cache, and re-open VS. You can find the schemas under something like:

C:\Documents and Settings\your username]\Application Data\Microsoft\VisualStudio\10.0\ReflectedSchemas

I tried without success.

Can someone help or explain why this happens?

_{Friday, November 5, 2010 4:03 AM}

Not working for me either .....

Now i am having another problem:

Warning 1 D:\MY Folder\mywebsite\Default.aspx: ASP.NET runtime error: Section or group name 'jsonSerialization' is already defined. Updates to this may only occur at the configuration level where it is defined. (D:\MY Folder\mywebsite\web.config line 16) D:\MY Folder\mywebsite\Default.aspx 1 1 D:\MY Folder\mywebsite\

_{Friday, November 5, 2010 2:13 PM}

What actually worked of me is I removed the Default Website from the IIS Manager.

Try it

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Element 'content' is not a known element. this can occur if there is a compilation error in the website, or the web.config file is missing.

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All replies (6)

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