YAML is a data serialization standard that is intended to be human friendly. For example, it reduces the use of delimiters quite drastically compared to other formats like JSON. Some YAML file authors might push the boundary for readability even further by having a property where the value can be a sequence with zero or more values, or just a scalar if there is only a single value. Reducing the number of delimiters someone has to read or write even further. How can this work with C#, a strongly typed language?

Recently, I was using a YAML file for storing some data for a pet project. To work with this YAML in a .NET application, I use the excellent YamlDotNet library by Antoine Aubry. One of my properties was a URL. Deserializing went fine, but when serializing back to a YAML file, things were not going as intended. In this short article, I will explain how I did fix this.