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

tip

You can suppress this inspection to ignore specific issues, change its severity level to make the issues less or more noticeable, or disable it altogether.

This is a solution-wide code inspection. It only works when the Solution-wide analysis is enabled.

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 will detect that Name and Age 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 either or both of the following:

• The simplified global usage checking is enabled — Show unused non-private type members when solution-wide analysis is off on the Code Inspection | Settings page of ReSharper options (Alt+R, O).

• The solution-wide analysis is enabled — Enable solution-wide analysis on the Code Inspection | Settings page of ReSharper options (Alt+R, O).

Note that even if a symbol has no direct usages in your solution and ReSharper warns you about it, there could be cases where symbols are used indirectly — for example, via reflection — or they could just be designed as public API. In all those cases you would want to suppress the usage-checking inspection for the symbol, and there are several ways to do so:

• The recommended way is to decorate the implicitly used symbols with code annotation attributes. There are two attributes for this purpose: [UsedImplicitly] and [PublicAPI], which are functionally similar, but let you and your teammates understand how the symbol is actually used.

• You can also suppress usage-checking inspections with any custom attribute. To do so, mark the definition of that attribute with the [MeansImplicitUse] attribute.

• And finally, you can suppress a specific usage-checking inspection as any other code inspection with a suppression comment or a suppression attribute.