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.

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}";
}

Public Class Person
	Public Name As String
	Public Age As Integer
	Public Sub New(name As String, age As Integer)
		Me.Name = name
		Me.Age = age
	End Sub
	Public Overrides Function ToString() As String
		Return String.Format("Name: {0}, Age: {1}", Name, Age)
	End Function
End Class

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 .

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

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:

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