Promote to Generic Parameter

• Aug 19, 2021
• 3 minutes to read

Purpose

Takes a class reference or struct reference inside a method block and turns that into a type parameter of the generic method. The Promote to Generic Parameter refactoring also updates all calling code.

This refactoring reduces the time it takes to make a method applicable to more classes in your code.

Availability

Available when the cursor is in a class reference or struct reference in a method.

How to Use

1. Place the caret in a class reference or struct reference in a method.

   C#

   using System;
   
   namespace ConsoleApp15
   {
       public class Verifier
       {
           public string CheckText(string text)
           {
               var validatedText = text ?? "";
               if (TrimSpaces)
                   validatedText = validatedText.Trim();
               return validatedText;
           }
           public bool TrimSpaces { get; set; }
       }
   
       interface SpellChecker
       {
           string Check(Verifier verifier, string text);
       }
   
       class Control : SpellChecker
       {
           void SetRules<V>(V verifier)
               where V : Verifier
           {
               verifier.TrimSpaces = true;
           }
           public string Check(Verifier verifier, string text)
           {
               SetRules<Verifier>(verifier);
               return verifier.CheckText(text);
           }
           public void LogText(string text)
           {
               string verifiedText = Check(new Verifier(), text);
               Console.WriteLine(verifiedText);
           }
       }
   }
   

   VB.NET

   Namespace ConsoleApp15
       Public Class Verifier
           Public Function CheckText(ByVal text As String) As String
               Dim validatedText = If(text, "")
               If TrimSpaces Then validatedText = validatedText.Trim()
               Return validatedText
           End Function
   
           Public Property TrimSpaces As Boolean
       End Class
   
       Interface SpellChecker
           Function Check(ByVal verifier As Verifier, ByVal text As String) As String
       End Interface
   
       Class Control
           Implements SpellChecker
   
           Private Sub SetRules(Of V As Verifier)(ByVal verifier As V)
            verifier.TrimSpaces = True
           End Sub
   
           Private Function Check(verifier As Verifier, text As String) As String Implements SpellChecker.Check
               SetRules(Of Verifier)(verifier)
               Return verifier.CheckText(text)
           End Function
   
           Public Sub LogText(ByVal text As String)
               Dim verifiedText As String = Check(New Verifier(), text)
               Console.WriteLine(verifiedText)
           End Sub
       End Class
   End Namespace
   

2. Press Ctrl+. or Ctrl+~ to invoke the Code Actions Menu.

3. Select Promote to Generic Parameter from the menu and press Enter.

   

After execution, this refactoring turns a regular method into a generic method.

C#

using System;

namespace ConsoleApp15
{
    public class Verifier
    {
        public string CheckText(string text)
        {
            var validatedText = text ?? "";
            if (TrimSpaces)
                validatedText = validatedText.Trim();
            return validatedText;
        }
        public bool TrimSpaces { get; set; }
    }

    interface SpellChecker
    {
        string Check<T>(T verifier, string text) where T : Verifier;
    }

    class Control : SpellChecker
    {
        void SetRules<V>(V verifier)
            where V : Verifier
        {
            verifier.TrimSpaces = true;
        }
        public string Check<T>(T verifier, string text) where T : Verifier
        {
            SetRules<T>(verifier);
            return verifier.CheckText(text);
        }
        public void LogText(string text)
        {
            string verifiedText = Check<Verifier>(new Verifier(), text);
            Console.WriteLine(verifiedText);
        }
    }
}

VB.NET

Namespace ConsoleApp15
    Public Class Verifier
        Public Function CheckText(ByVal text As String) As String
            Dim validatedText = If(text, "")
            If TrimSpaces Then validatedText = validatedText.Trim()
            Return validatedText
        End Function

        Public Property TrimSpaces As Boolean
    End Class

    Interface SpellChecker
        Function Check(Of T As Verifier)(ByVal verifier As T, ByVal text As String) As String
    End Interface

    Class Control
        Implements SpellChecker

        Private Sub SetRules(Of V As Verifier)(ByVal verifier As V)
            verifier.TrimSpaces = True
        End Sub

        Private Function Check(Of T As Verifier)(verifier As T, text As String) As String Implements SpellChecker.Check
            SetRules(Of T)(verifier)
            Return verifier.CheckText(text)
        End Function

        Public Sub LogText(ByVal text As String)
            Dim verifiedText As String = Check(Of Verifier)(New Verifier(), text)
            Console.WriteLine(verifiedText)
        End Sub
    End Class
End Namespace