Telerik doesn't work after moving project to another env


i moved my project from one env, and from then on i have issue running my application.

The error i receive below. 'Could not load file or assembly 'Telerik.Web.UI, Version=2016.2.504.45, Culture=neutral, PublicKeyToken=121fae78165ba3d4' or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)'
asked on Stack Overflow Apr 18, 2018 by Ezell Buoee

1 Answer


The error code 0x80131515 usually tells that the assembly file has been blocked or not referenced properly (because VS thinks referenced assembly still untrusted). Here is an explanation from Telerik's FAQ:

Operation is not supported HRESULT: 0x80131515

The HRESULT: 0x80131515 error usually means that the file was downloaded from the Internet and Windows has blocked it. In such cases you need to simply do the following:

  1. In Windows Explorer, right-click the file.
  2. Select Properties
  3. Click the Unblock button.
  4. Clear the read-only attribute.

Other things you should try to solve this issue:

Using bin folder assembly deployment

  • Copy Telerik assemblies to \bin folder and use reference from that folder.
  • Restart VS IDE.

Using GAC assembly deployment

  • Add Telerik.Web.UI.dll assembly to GAC using this command:

    gacutil /i "[InstallDir]\BinXX\Telerik.Web.UI.dll

    Note: [InstallDir] belongs to Telerik location path and "X" means numeric value which should be adjusted based on folder hierarchy.

  • Remove previously used Telerik.Web.UI.dll from bin folder and add reference to the newer one.

  • Ensure that this line exists in web.config:

    <add assembly="Telerik.Web.UI, Version=2016.2.504.45, Culture=neutral, PublicKeyToken=121FAE78165BA3D4" />
  • Restart VS IDE.

If all possible solutions above are fruitless, create a new project with current Telerik assembly and all required assemblies then move old project files into new project.

Additional references:

Could not load file or assembly 'Telerik.Web.UI'

Upgrade Compile Error

Visual Studio Project Sample Loading Error: Operation is not supported. (Exception from HRESULT: 0x80131515)

answered on Stack Overflow Apr 19, 2018 by Tetsuya Yamamoto

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