这是最常用的重构之一，我们经常要用到它，因为我们的代码中经常因为这或那的原因产生重复代码，让我们来看下面的例子：
1: public class MedicalRecord
2: {
3: public DateTime DateArchived { get; private set; }
4: public bool Archived { get; private set; }
5:
6: public void ArchiveRecord()
7: {
8: Archived = true;
9: DateArchived = DateTime.Now;
10: }
11:
12: public void CloseRecord()
13: {
14: Archived = true;
15: DateArchived = DateTime.Now;
16: }
17: }
下面是我们重构后的代码，请记住只要有可能就请应用该重构，因为这可以帮你减少代码中的bug数量，另外请牢记DRY(don’t repeat yourself)原则，尽量不要复制/粘贴代码。
1: public class MedicalRecord
2: {
3: public DateTime DateArchived { get; private set; }
4: public bool Archived { get; private set; }
5:
6: public void ArchiveRecord()
7: {
8: SwitchToArchived();
9: }
10:
11: public void CloseRecord()
12: {
13: SwitchToArchived();
14: }
15:
16: private void SwitchToArchived()
17: {
18: Archived = true;
19: DateArchived = DateTime.Now;
20: }
21: }
原文链接：http://www.lostechies.com/blogs/sean_chambers/archive/2009/08/15/refactoring-day-15-remove-duplication.aspx