Normalization of Strings With String.ToUpperInvariant()
I am currently storing normalized versions of strings in my SQL Server database in lower case. For example, in my Users table, I have a UserName and a LoweredUserName field. Depending on the context, I either use T-SQL’s LOWER() function or C#’s String.ToLower() method to generate the lower case version of the user name to fill the LoweredUserName field. According to Microsoft’s guidelines and Visual Studio’s code analysis rule CA1308, I should be using C#’s String.ToUpperInvariant() instead of ToLower(). According to Microsoft, this is both a performance and globalization issue: converting to upper case is safe, while converting to lower case can cause a loss of information (for example, the Turkish ‘I’ problem).