1. Single Value Objects as C# structs
Domain-Driven Design bottom-up
Corniel Nobel, , A’dam

2. About me
Corniel Nobel Energetic, optimistic, creative, out of the box thinking, experienced software engineer
Exact (2014-current)
Senior software engineer
Qowaiv community (2013-current)
Founding member
TJIP ( )
OGD ICT-diensten ( )
IT-Professional
2B Insite ( )
Software engineer

3. Program Structs in C# DDD in short Single Value Objects Design choices
Qowaiv
Demo
Questions
Program 3
- Single Value Objects as C# structs

4. Structs in C# 4
- Single Value Objects as C# structs

5. Reference Types & Value Types
Pointer to data elsewhere in memory
Mutable by default
Inheritable by default
Examples
Object
String*
Type[]
Value Type
Stores own data (or point to data)
Immutable by design*
Sealed by design
Examples
Single, Double, Decimal
Byte, SByte
Int16, Int32, Int64
UInt16, UInt32, UInt64
Boolean, Char, DateTime, Guid 5
- Single Value Objects as C# structs

6. DDD in short 6
- Single Value Objects as C# structs

7. DDD in short Domain Subject area of the software Model Repositories
Aggregate roots
Entities
(Single) Value Objects
Ubiquitous Language
Language structured around the domain
(Bounded) Context 7
- Single Value Objects as C# structs

8. Single Value Objects 8
- Single Value Objects as C# structs

9. Single Value Objects in DDD
Subset underlying primitive type
Self-descriptive
Immutable
Equal by value 9
- Single Value Objects as C# structs

10. Example SVO’s Percentage Date Week date Year Month Country Currency
Stream size
UUID
Seed
SQL Timestamp
Initials
Gender
House number
address
Postal Code
BMI
IBAN
BIC
BSN
License plate
Elo 10
- Single Value Objects as C# structs

11. Example Stream Size
var size = StreamSize.FromMegaBytes(12.4); var size = StreamSize.Parse("13 kb"); StreamSize size = 1400; Console.WriteLine("The file was {0:0.0 F}.", size); // The file was 13.0 Kilobyte 11
- Single Value Objects as C# structs

12. Example Postal Code
var code = PostalCode.Parse("1234ab"); if (code.IsValid(Country.BE)){ /* ... */ } Console.WriteLine(“Your postal code: {0:NL}", code); // Your postal code: 1234 AB 12
- Single Value Objects as C# structs

13. Example IBAN
var iban = IBAN.Parse("nl20ingb "); Console.WriteLine(“Your IBAN: {0:F}", iban); // Your IBAN: NL20 INGB 13
- Single Value Objects as C# structs

14. Design Choises 14
- Single Value Objects as C# structs

15. Creation & conversion No (public) constructor
Parse(string) & TryParse(string)
Create(underlying) & TryCreate(underlying)
TypeConverter
Casting
String (explicit)
Underlying type (implicit and/or explicit) 15
- Single Value Objects as C# structs

16. Validation Potential valid False positive/negative IsValid()
Context independent
IsValid(context) 16
- Single Value Objects as C# structs

17. Serialization RunTime Serializable Attribute System.Iserializable
Ctor(SerializationInfo, StreamingContext)
XML
System.Xml.IXmlSerializable
JSON
void FromJson()
void FromJson(String;Int64;Double;DateTime)
Object ToJson() 17
- Single Value Objects as C# structs

18. Formatting & debugging
IFormattable
ToString()
ToString(string)
ToString(IFormatProvider)
ToString(string, IFormatProvider)
[DebuggerDisplay("{DebuggerDisplay }")]
private string DebuggerDisplay { get; }
Unified internal string representation* 18
- Single Value Objects as C# structs

19. Qowaiv 19
- Single Value Objects as C# structs

20. Qowaiv community Open Source .NET library MIT licence Code generator
GitHub
github.com/Corniel/qowaiv
NuGet packages
Qowaiv
Qowaiv.Web
Qowaiv.Json.Newtonsoft 20
- Single Value Objects as C# structs

21. 21
- Single Value Objects as C# structs

22. Questions? 22
- Single Value Objects as C# structs

23. Disclaimer
This document contains certain statements and expectations that are forward looking, and which are based on information and plans that are currently available. By their nature, such forward-looking statements and expectations generate risk and uncertainty because they concern factors and events in the future and depend on circumstances that may not occur.
Unforeseen factors that could influence the statements and expectations may, for instance, be changes in expenditures by companies in the markets we operate in; economic, political and foreign exchange fluctuations; possible statutory changes; changes in salary levels of employees; or future takeovers and divestitures.
Exact can therefore not guarantee the accuracy and completeness of such statements and expectations, nor that such statements and expectations will be realized. Actual results may differ materially. Exact refuses to accept any obligation to update statements made in this document.

24. Exact. Cloud business software.