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Answer: The parameters are in scope throughout the type body.

public class OrderService(IOrderRepo repo, ILogger<OrderService> log) {
  public Order Get(int id) {
    log.LogInformation("Get {Id}", id);
    return repo.Find(id);
  }
}

Other constructors must chain

Additional constructors must call the primary one with this(...):

public class Point(int x, int y) {
  public Point() : this(0, 0) {}
  public int X => x;
}

If a class has no explicit constructor, C# supplies a parameterless one; declaring a primary constructor replaces that default.

Claims

• id: C1 claim: C# 12 introduces primary constructors. source: S1 evidence: "C# 12 introduces primary constructors"
• id: C2 claim: Primary constructor parameters aren't members of the class. source: S1 evidence: "Primary constructor parameters aren't members of the class."
• id: C3 claim: Primary constructor parameters don't become properties, except in records. source: S1 evidence: "Primary constructor parameters don't become properties, except in record types."
• id: C4 claim: A constructor can call another using the this keyword. source: S2 evidence: "To do that, use the this keyword."
• id: C5 claim: C# provides a parameterless constructor if none is declared. source: S2 evidence: "C# provides a parameterless constructor that you can use to instantiate an instance"

Sources

• [S1] Declare C# primary constructors – classes, structs. Microsoft Learn (.NET docs). https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/tutorials/primary-constructors . License: CC BY 4.0 (dotnet/docs). Accessed 2026-11-04.
• [S2] Instance constructors - C#. Microsoft Learn (.NET docs). https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/instance-constructors . License: CC BY 4.0 (dotnet/docs). Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_5wv1yt3d,
  author = {{iinventedlight}},
  title = {{C\# primary constructors}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/csharp-primary-constructors/},
  note = {Permanent ID iil:note:5wv1yt3d. License: CC-BY-4.0.},
}

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