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Jan Reilink

My name is Jan. I am not a hacker, coder, developer or guru. I am merely a systems administrator, doing my daily thing at Vevida.

How to fix System.Collections.Generic.KeyNotFoundException “The given key was not present in the dictionary” Exception with MySQL Connector/NET and utf8mb4 character set

An System.Collections.Generic.KeyNotFoundException “The given key was not present in the dictionary” can be the result of using a too old MySQL Connector/NET version in your ASP.NET web application. A KeyNotFoundException is thrown when an operation attempts to retrieve an element from a collection using a key that does not exist in that collection. An unsupported character set like utf8mb4 can be such a key, if your Connector/NET doesn’t support this character set. Luckily there is an easy workaround for this.

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Reduce Wordfence CPU usage, disable Wordfence “Live Traffic View”

Whenever WordPress is using a lot of CPU and you have Wordfence Security plugin enabled, it is recommended to double check some settings. Unfortunately the Wordfence “Live Traffic Options” (“Traffic logging mode”) feature can cause high CPU usage and load issues for WordPress websites. Therefore, I recommend you disable this feature to improve the performance of your WordPress website.

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Install Windows Server Servicing Stack Updates (SSU) using PowerShell

You can install Servicing Stack Updates (SSU) for Windows Server 2012R2, 2016 and Windows Server 2019 using PowerShell, without downtime. Because they must be installed prior to your normal Windows Server security updates, you can install them anytime you want to during the day. Here’s a small PowerShell example to do so.

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Automatically flush Redis cache after publishing a WordPress post

In a previous post I explained that clearing PHP opcode caches before WordPress Updates helps in streamlining the update process. WordPress updates no longer fail because of cached file locations. Did you know you can automatically flush opcode caches like Redis when you publishing a post or page in WordPress? Doing so ensures you and your visitors see the newly created content immediately.

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How to uninstall and remove Adobe Flash Player in Windows Server

Ever wondered why Windows Server Update Services (WSUS) offers Flash updates for Windows Server? Adobe Flash Player is installed on Windows Server 2016 / 2019 if you have the Remote Desktop Session Host (RDSH) role installed. Yikes! I can imagine you want to delete Adobe Flash Player without deleting the RDSH role, and here is how.

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WordPress .htaccess security best practices in Apache 2.4.6+

Apache Access Control done right in WordPress .htaccess, ‘Allow/Deny from all’ versus ‘Require All Granted/Denied’

Since Apache 2.4.6, a new module is used to configure and set up access control for websites: mod_authz_core. This means you have to use a different syntax for allowing or blocking hosts and IP addresses to your website. But unfortunately, old documentation is never updated and people even still write blog posts using that old syntax, leaving you with an unprotected website. Not what you had in mind, now is it?…

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Manually failover all databases in an SQL Server Database Mirroring configuration

How to manually failover an SQL Server database mirroring session?

How to manual failover mirrored SQL Server databases using Transact-SQL (T-SQL) in SQL Server 2017+. This can only be initiated from the principal server, and the mirrored database must be synchronized (that is, when the database is in the SYNCHRONIZED state). In this article I’ll show you how to force a failover.

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ASP and ASP.NET connection string examples for Microsoft SQL Server and MySQL

A connection string is sometimes a bit obscure. Do I need ODBC or OLE DB? When you need one and Google for it, you often find old ones that either don’t work at all anymore, or are not optimal. This article provides you with a couple of ASP.NET to SQL Server connection string examples, and as a bonus for ASP to MySQL too.

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