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.
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.
Simple MySQL connection test from your website with ASP.NET, PHP & classic ASP. Whenever you need a MySQL connectivity test from a website or server, it’s handy to have various test scripts nearby. Whether it is because you are setting up a new website or you have just installed a new server and are running your tests.