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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, ReSharper 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 Code Inspection | Settings page of ReSharper options Alt+R, O.

  • Solution-wide analysis: select Enable solution-wide analysis on the Code Inspection | Settings page of ReSharper options Alt+R, O.

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: