C# Tip: Using JsonConverter for Targeted and Global JSON Data Formatting

A practical C# guide demonstrates how to build a custom JsonConverter that capitalizes the first letter of string values during JSON deserialization. The converter, named UpperCaseFirstCharConverter, is designed for data-import scenarios where incoming JSON fields like names may have inconsistent casing. Developers can apply it globally via JsonSerializerOptions or register it in ASP.NET Core's Program.cs to cover all serialization operations. However, global application affects all string fields, including unintended ones like state codes, which can cause data errors. The recommended fix is to apply the converter selectively using the JsonConverter attribute directly on specific model properties such as FirstName and LastName.