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2024.3
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Code inspection: Field can be made readonly (non-private accessibility)

Last modified: 11 February 2024

Say you have decided to make a Person class, initialized only via the constructor, but with publicly available fields. You go ahead and implement the following:

public class Person
{
  public string Name;
  public int Age;
  public Person(string name, int age)
  {
    Name = name;
    Age = age;
  }
  public override string ToString() =>
    $"Name: {Name}, Age: {Age}";
}

If solution-wide inspection is enabled, JetBrains Rider can detect that the fields are only being assigned in the constructor and offers to create an additional safeguard: by marking them readonly, we get to ensure that neither this class nor its users will inadvertently assign new values to these fields.

For the solution-wide inspection to work, you need to enable at least one of the following:

  • Simplified global usage checking: select Show unused non-private type members when solution-wide analysis is off on the Editor | Inspection Settings page of JetBrains Rider settings CtrlAlt0S.

  • Solution-wide analysis: select Enable solution-wide analysis on the Editor | Inspection Settings page of JetBrains Rider settings CtrlAlt0S.

Note that even if the reported field has no direct usages in your solution, there could be cases where it is used indirectly — for example, via reflection — or it could just be designed as public API. In all those cases, you would want to suppress the usage-checking inspection for the field in one of the following ways: