virtual ,abstract,override 用法

abstract:

抽像一个方法或一个类,抽像一个类时如下:

public abstract class MigrateBase
{

protected abstract List<string> NeedReplaceColumn { get; }

}

MigrateBase 就可以做为其它类的基类,NeedReplaceColumn 属性在其的子类中则必须重写,就是说的override,而且abstract 在声名方法或属性时,实现不要写;

virtual:

虚拟一个方法,如下

public abstract class MigrateBase
{

        protected virtual List<string> NeedReplaceColumn
        {

            get
            {

                List<string> numlist = new List<string>(){

                {"one"},

                {"two"}

                };

                return numlist;
            }
        }

}

virtual 在子类继承MigrateBase时可以override,也可以不override,不override的话,NeedReplaceColumn的值就是List<string>(){{"one"},{"two"}};

如果override 后,如下:

   public  class MigratePatientsDocuments : MigrateBase
    {

       protected override List<string> NeedReplaceColumn
        {

            get
            {

                List<string> numlist = new List<string>(){

                {"three"},

                {"four"}

                };

                return numlist;
            }
        }

      那么在运行MigratePatientsDocuments类时,NeedReplaceColumn的值就是:

List<string>(){

                {"three"},

                {"four"}

                };

override:

  重载方法,父类有abstract的方法里,子类一定要对该方法override,而virtual的方法,可以不用.