ReSharper 2017.2 Help

Generating Relational Members

ReSharper | Edit | Generate Code | Relational Comparer
Alt+Insert | Relational Comparer
ReSharper_GenerateRelationalComparer

ReSharper helps you helps you automatically overload relational opeartors and implementations of related interfaces using selected fields and properties. By default, ReSharper will create an implementation of IComparable<T>, and optionally, operators >, <, and as well as an implementation of IComparable are generated too.

In the example below, this command is used to generate relational members that takes into account int _birthYear and string _name fields when to compare objects of the Person class.

Before generationAfter generation
class Person { private int _birthYear; private string _name; }
class Person : IComparable<Person>, IComparable { private int _birthYear; private string _name; public int CompareTo(Person other) { if (ReferenceEquals(this, other)) return 0; if (ReferenceEquals(null, other)) return 1; var birthYearComparison = _birthYear.CompareTo(other._birthYear); if (birthYearComparison != 0) return birthYearComparison; return string.Compare(_name, other._name, StringComparison.Ordinal); } // Optionally: Implementation of IComparable and relational operators public int CompareTo(object obj) { if (ReferenceEquals(null, obj)) return 1; if (ReferenceEquals(this, obj)) return 0; if (!(obj is Person)) throw new ArgumentException($"Object must be of type {nameof(Person)}"); return CompareTo((Person) obj); } public static bool operator <(Person left, Person right) { return Comparer<Person>.Default.Compare(left, right) < 0; } public static bool operator >(Person left, Person right) { return Comparer<Person>.Default.Compare(left, right) > 0; } public static bool operator <=(Person left, Person right) { return Comparer<Person>.Default.Compare(left, right) <= 0; } public static bool operator >=(Person left, Person right) { return Comparer<Person>.Default.Compare(left, right) >= 0; } }

To generate relational members

  1. In the editor, set the caret on the type name or within a type at the line where you want to insert relational members. If the caret is on the type name, generated code will be added in the beginning of the type declaration.
  2. Press Alt+Insert or choose ReSharper | Edit | Generate Code… in the main menu.
  3. In the Generate pop-up menu, select Relational Comparer.
  4. In the Generate dialog that appears, you will see a list of properties and fields. Select the members that you want to use for type comparison.
    Generating relational members with ReSharper

    If there are no fields/properties in your type or you do not select any of them, ReSharper, depending on your settings, throws new NotImplementedException(), returns default value, or puts code that will not compile in the body of the generated methods. You can configure the settings on the Code Editing | Members Generation page of ReSharper options.

    Optionally, use the following controls in the dialog:

    • Fields can be null — appears if there are any nullable fields or properties in your type. By default, this check box is selected, meaning that ReSharper will generate null checks for selected fields. You can clear this check box if you do not need null checks.
    • String comparison — appears if there are any string fields in your type. ReSharper will generate string.Compare(string, string, StringComparison) for the selected strings, and the selector lets you choose which value should be generated for the StringComparison argument.
    • CompareTo already exists — appears if an implementation of CompareTo() already exists and lets you choose whether to:
      • Replace the method if it already exists.
      • Put the newly generated method side by side with the existing one.
      • Skip generating a new method altogether.
    • Implement IComparable interface — tick this checkbox to generate an implementation of IComparable interface in addition to IComparable<T>, i.e. generate the CompareTo(object) method in addition to CompareTo(T).
  5. Click Finish to complete the wizard.
    You can also click Options to review or modify common code generation preferences on the Code Editing | Members Generation page of ReSharper options.

This feature is supported in the following languages and technologies:

Language: C#
Language: VB.NET
Language: C++
Language: HTML
Language: ASP.NET
Language: Razor
Language: JavaScript
Language: TypeScript
Language: CSS
Language: XML
Language: XAML
Language: Resx
Language: Build Scripts
Language: Protobuf
Language: JSON
Feature is available Feature is available Feature is available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available Feature is not available

The instructions and examples given here address the use of the feature in C#. For details specific to other languages, see corresponding topics in the ReSharper by Language section.

Last modified: 10 November 2017

See Also