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JSON: Javascript Object Notation

  • a very popular method of exchanging data across the web
  • commonly corresponds with AJAX
  • used by many other languages and programs
    • human-readable
    • hierarchical
    • lightweight way to exchange data -- it's just a string
    • similar to XML but more better
  • using an extension like json view or other tools can make it look cleaner
  • formatting JSON: you can use array notation or object notation, and you can combine the two
  • array notation: just a 'grocery list' of values
    • it's easy, efficient
    • however it takes a lot of overhead to keep track of what each value means
    • example: ['string', 423, true, [1,2,3]]
  • object notation: uses property-value pairs
    • the name of a property and the value of that property. example: "name": "Smith"
    • good for more complex objects
  • example of a simple JSON file that combined object and array notation: 
     [
 	{
 		"name": "Jim",
 		"age": 20,
 		"phone": "502-214-4243",
 		"cars":["Peugeot"]
 	},
 	{
 		"name": "Felicia",
 		"age": 32,
 		"phone": "502-214-4243",
 		"cars":["Audi", "BMW", "Fiat"]
 	},
 	{
 		"name": "Maude",
 		"age": 56,
 		"phone": "502-214-4243",
 		"cars":["Chevy", "Jeep"]
 	}
 ]
    • note that in properly formatted JSON object notation, both the property and its value must be surrounded in double quotes
    • if a JSON file isn't properly formatted, you'll usually end up with a JS error
    • to find out if it's properly formatted or not, use an online validator like JSONlint.com

Serialization and Deserialization in C#

  • microsoft doc
  • serialization is sometimes referred to as encoding and means to turn an object into a string
  • deserialization is sometimes referred to as decoding and means to turn a string into an object

Deserialization to .NET Objects

  • JsonSerializer.Serialize
  • can be synchronous or async

Default Behavior

  • all public properties are serialized. you can specify which properties to ignore with [JsonIgnore]
  • the default encoder escapes non-ASCII characters, HTML-sensitive characters within the ASCII-range, and characters that must be escaped according to the RFC 8259 JSON spec
  • json is minified but can be prettified with the WriteIndented option
  • casing will match the .NET names but can be customized
  • circular references are detected and throw exceptions. configuration can be added to preserve and handle circular references
  • fields are ignored but can be included with the IncludeFields option
  • order of serialized properties can be customized (why is this useful again?)
  • supported types:
    • .NET primatives that map to js primatives such as numeric types, strings, and Boolean
    • user-defined CLR objects (POCOs)
    • one-dimensional and jagged arrays
    • collections and dictionaries from select namespaces
    • custom converters can be added to handle additional type conversions

Deserialization to .NET Objects

  • to read json, create a class with properties and fields that match the json structure
  • JsonSerializer.Deserialize
  • can be synchronous or async
  • any json properties that are not represented in the class are ignored
  • if any properties on the type are required but not present in the json payload, deserialization will fail (?????)
  • COOL TRICKS!
    • if you only need a subsection of the json and don't have a full class to represent the whole payload, you can deserialize into a JSON DOM and then extract what you need from the DOM
    • VS2022 can automatically generate a class from json! create a new class file and delete the template code, then Edit > Paste Special > Paste JSON as Classes

Default Behavior

  • property name matching is case-sensitive but can be configured
  • if json contains data for a read-only property, the value is ignored and no exception is thrown
  • non-public constructors are ignored
  • immutable types with no public set can be deserialized to with [JsonConstructor] attribute
  • enums are supported as numbers but they can be serialized as strings (and then deserialized to strings)
  • fields are ignored but can be included with the IncludeFields option or [JsonInclude] attribute
  • comments and trailing commas in the json throw exceptions but can be handled
  • default max depth for deeply nested json is 64

Summary of .NET Serialization Gotchas

  • fields and private properties won't be handled unless you handle them
  • when deserializing, values for read-only properties will be ignored and no exception will be thrown (sneaky!)
  • casing must match unless otherwise specified
  • circular references, comments and trailing commas will bork your process unless you handle them
  • deep json may not completely transfer (default max depth 64)