Kentico 9 Sudden Malfunction

Fuad Dahlan asked on June 1, 2018 05:33

Hi, recently I try to run the website and I got this message "CS1660: Cannot convert lambda expression to type 'System.Collections.Generic.IEqualityComparer

Correct Answer

Juraj Ondrus answered on August 7, 2018 15:51

The issue is described in this KB Article

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Recent Answers


Michal Samuhel answered on June 1, 2018 07:47 (last edited on June 1, 2018 07:48)

Hi Fuad,

This happens due to windows and .NET update where microsoft added a method with same signature as the one we had already created within our API. The solution:

Upgrade to v10 or higher

Roll back the Windows update

Use web application project

Change code in \CMS\App_Code\CMS\UpgradeProcedure.cs: From: .ToDictionary(group => group.Key, group => group.Select(u => u.Email).ToHashSet(StringComparer.InvariantCultureIgnoreCase));

To: .ToDictionary(group => group.Key, group => CMS.DataEngine.DataExtensions.ToHashSet(group.Select(u => u.Email), StringComparer.InvariantCultureIgnoreCase));

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