Unknown server tag 'asp:ScriptManager'.

Question

I am using Ajax Controls and when I run my site getting following error:

Unknown server tag 'asp:UpdatePanel'.

When I searched on google about this error, most of the article saying to use the code given below:

--------------------------------

<system.web>

<pages>

</controls>

</pages>

:::::::::::::::

</system.web>

-------------------------------

After using above code in config file I am still getting more errors as given below:

------------------------------

The type 'System.Web.UI.IScriptControl' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.

The type or namespace name 'AsyncPostBackTrigger' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)

The type or namespace name 'ScriptManager' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)

The type or namespace name 'UpdatePanel' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)

The type or namespace name 'UpdatePanelTriggerCollection' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)

---------------------------------

Do I have to add some lines in Default.aspx page like given below or some namespaces:

<%@ Register TagPrefix="cc" Namespace="Winthusiasm.HtmlEditor" Assembly="Winthusiasm.HtmlEditor" %>

One more markable thing when I use <compilation debug="true" targetFramework="4.0" /> in cofig file it solves all errors. But my hosting company provides 3.5 extension.

How I fix this issue, please help.
Thanks in advance.

Suthish Nair · Answer

You try these two options. 1. Go to menu Website ==> Start Options ==> Build ==> Change the Target Framework to 3.5 2. Else create the project in 3.5 framework.

Abhimanyu K Vatsa · Answer

thanks for quick reply Suthish Yes I am using AjaxControlToolKit and I my web.config file is clean. in cofig file it solves all errors. But my hosting company provides 3.5 extension. How to manage the .net version that's the issue?

Suthish Nair · Answer

Are you using AjaxControlTool Kit? Remove all Ajax reference from web.config dll's etc. rebuild the project.

Ravikumar G · Answer

Hi Abhi Even I'm facing the same type of Issue. My application is targetting .net 2.0 and works fine. I need to test some of the test cases by setting my system date back to say 01/01/2014. Then getting script errors which are similar to above you mentioned. Since last two weeks I'm searching for this solution hope you many know. Did you ever faced this type of issues. Thanks..

Thiru Kumaran · Answer

I add the following code in my web.config file it works

Abhimanyu K Vatsa · Answer

Thanks Suthish for your all effort here.

Abhimanyu K Vatsa · Answer

Issue has been fixed. By using some lines in config file