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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Iain Waddell answered on August 21, 2018 17:03 (last edited on August 21, 2018 17:05)

Do you have details about the .NET update that causes the problem?

Just hit the problem on my development machine and the code change worked, but would be handy to know which update caused the problem.

Edit: Just seen the KB link on the page, so please ignore.

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