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    Could not load file or assembly 'Microsoft.Windows.Design.Extensibility ...'

    Error Description

    When you use DevExpress ASP.NET products together with the AjaxControlToolkit, the following errors can occur:

    • Could not load file or assembly ‘Microsoft.Windows.Design.Extensibility …’
    • Could not load file or assembly ‘X’

    This problem usually occurs when DevExpress.*.Design.dll assembly files exist in the application Bin folder. These files are intended for development purposes only. Note that DevExpress.*.Design.dll assembly files cannot be distributed according to our EULA terms.

    Solution

    1. Remove all DevExpress.*.Design.dll files from the application Bin folder and exclude them from deployment.
    2. Clear the following directory: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\.
    3. Rebuild the application.
    4. Redeploy the application without DevExpress.*.Design.dll assembly files.