Solved: “Unknown server tag telerik:RadScriptManager”

If you are using third-party .NET component libraries such as Telerik or DevExpress, you may come across the error message below while trying to include controls in your page.

Server Error in ‘/TestASPNET’ Application.

Parser Error
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: Unknown server tag ‘telerik:RadScriptManager’.


Make sure to include 2 DLL files below in your project references of Visual Studio:

  • Telerik.Web.UI
  • Telerik.Web.UI.Skins

If you are still receiving the error above, add a reference to your Telerik assembly in your web.config file. You can use the following lines to make this reference.

  <pages viewStateEncryptionMode="Always" controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID">
      <add tagPrefix="telerik" namespace="Telerik.Web.UI" assembly="Telerik.Web.UI"/>

Solved: “Unrecognized tag prefix or device filter ‘telerik'”

I came across “unrecognized tag prefix” error while trying to use Telerik’s ASP.NET AJAX controls. Here is how the error message looks like:

Warning – Unrecognized tag prefix or device filter ‘telerik’


  1. Make sure to add Telerik DLLs into the bin folder of your project
  2. Add the following handlers into your web.config file (in section):

            <add tagPrefix="telerik" namespace="Telerik.Web.UI" assembly="Telerik.Web.UI"/>
          <add path="ChartImage.axd" type="Telerik.Web.UI.ChartHttpHandler" verb="*" validate="false"/>
          <add path="Telerik.Web.UI.SpellCheckHandler.axd" type="Telerik.Web.UI.SpellCheckHandler" verb="*" validate="false"/>
          <add path="Telerik.Web.UI.DialogHandler.aspx" type="Telerik.Web.UI.DialogHandler" verb="*" validate="false"/>
          <add path="Telerik.RadUploadProgressHandler.ashx" type="Telerik.Web.UI.RadUploadProgressHandler" verb="*" validate="false"/>
          <add path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" verb="*" validate="false"/>

Similar solutions apply to the same type of message for other components.

How to use Oracle “OPatch Utility” to find out information about Oracle Home

Oracle has a useful tool to list information about its products: OPatch Utility. You can apply patches or get information about the installed updates by using this command line tool.

One of the commands that come with this tool is lsinventory. It lists the patches applied to Oracle Home.


  1. Search for “OPatch” in Windows
    There might be several folders with this name if you have installed Oracle Data Access Components (ODAC) more than once
  2. Open command prompt in the actively used “OPatch” fodler
  3. Run the command below
opatch lsinventory