Ehsan Ghanbari

Experience, DotNet, Solutions

Extract method refactoring in C#

One of the best ways refactor a long method is to break it up into several methods. The extract method refactoring enable you to do this by selecting a block of code and select the Extract method and create a refactored extract method. Extract Method is just a refactoring operation that provides an easy way to create a new method from a code fragment in an existing member. You can create a new method by extracting a selection of code from inside the code block of an existing member. Take a look at this example (don’t mention about the functionality of this method, I'm just going to refactor this method)

  1.        public override string[] GetRolesForUser(string username)
  2.         {
  3.             using (var statosContext = new StatosContext())
  4.             {
  5.                 var user = statosContext.Account.SingleOrDefault(u => u.UserName == username);
  6.                 if (user == null)
  7.                     return new string[] { };
  8.                 return user.UserRoles == null ? new string[] { } :
  9.                   user.UserRoles.Select(u => u.Role).Select(u => u.RoleName).ToArray();
  10.             }
  11.         }

If you are want to refactor the this , select the block of the code just like the picture




After selecting the Extract method, select a name for the extracted method (I selected RolesForUser)

  1.      public override string[] GetRolesForUser(string username)
  2.         {
  3.             using (var statosContext = new StatosContext())
  4.             {
  5.                 return RolesForUser(username, statosContext);
  6.             }
  7.         }
  9.         private static string[] RolesForUser(string username, StatosContext statosContext)
  10.         {
  11.             var user = statosContext.Account.SingleOrDefault(u => u.UserName == username);
  12.             if (user == null)
  13.                 return new string[] {};
  14.             return user.UserRoles == null
  15.                        ? new string[] {}
  16.                        : user.UserRoles.Select(u => u.Role).Select(u => u.RoleName).ToArray();
  17.         }


Now, this is a refactored code on extract method. I know there was no need in this method to refactor it, but in real world programming you definitely will have this kinds of method which should be extracted to separated methods. 

About Me

Ehsan Ghanbari

Hi! my name is Ehsan. I'm a developer, passionate technologist, and fan of clean code. I'm interested in enterprise and large-scale applications architecture and design patterns. I spend a lot of time on software architecture. Since 2008, I've been as a developer for different companies and organizations and I've been focusing on Microsoft ecosystem all the time. During the past years, Read More

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