.NET Configuration File Corrupts On Write

.NET configuration files are designed to be customized with custom sections (System.Configuration.ConfigurationSection) and section groups (System.Configuration.ConfigurationSectionGroup). To do so, developers subclass these base classes to implement their custom functionality and incorporate them into the configuration file. .NET configuration files are XML files and follow a defined schema. It is somewhat complex but the relevant schema element in this article is the declaration section at the beginning () which declares the layout and types of sections and section groups used in the configuration file. This allows the .NET configuration mechanisms to properly instantiate your custom classes with configuration information. When modifying the configuration file programmatically, sometimes the addition of new section groups corrupts the configuration file when re-written preventing it from being read in the future. This article is a case study of such a situation.