Code inspection: Auto-property can be made get-only (non-private accessibility)

Starting from C# 6.0, you can define get-only auto-properties, which (similarly to readonly fields) can be only initialized via a constructor or an initializer. JetBrains Rider detects and helps you remove the redundant set accessor on auto-properties that are initialized from the constructor/initializer and have no write usages.

In the example below, an immutable class is intended, and once the value for the Name property is checked for nullability in the constructor, it can be safely used without further null checks. However, the private setter does not guarantee that the property will not be changed later in private members. Therefore, it is a good idea to make this property get-only to prevent any modifications.

public class Person
{
    public string Name { get; set; } // Auto-property can be made get-only

    public Person(string name)
    {
        Name = name ?? throw new ArgumentNullException(nameof(name));
    }

    public override string ToString()
    {
      return $"NAME: {Name.ToUpper()}";
    }
}
    

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

Note that even if the reported property setter 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 property setter in one of the following ways:

The recommended way is to decorate the implicitly used property setter 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 property setter 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.

Last modified: 11 February 2024