重構指南 - 移除重覆內容（Remove Duplication）

在項目中或多或少的都存在著重覆的或者功能相似的代碼，如果要對代碼做改動，就要修改多個地方，所以我們需要將多處重覆的代碼提取到一個公共的地方供統一調用，以減少代碼量，提高代碼可維護性。

重構前代碼

public class MedicalRecord
{
    public DateTime DateArchived { get; private set; }
    public bool Archived { get; private set; }

    public void ArchiveRecord()
    {
        Archived = true;
        DateArchived = DateTime.Now;
    }

    public void CloseRecord()
    {
        Archived = true;
        DateArchived = DateTime.Now;
    }
}

重構後代碼

public class MedicalRecord
{
    public DateTime DateArchived { get; private set; }
    public bool Archived { get; private set; }

    public void ArchiveRecord()
    {
        SwitchToArchived();
    }

    public void CloseRecord()
    {
        SwitchToArchived();
    }

    private void SwitchToArchived()
    {
        Archived = true;
        DateArchived = DateTime.Now;
    }
}