调用父类方法时，如何与子类方法，在锁对象不是同一个实例下，能线程安全，请见下面三种情况。
case1：
如下代码，在调用父类的方法时，和子类的方法，发生线程安全问题。原因的锁对象的实例不是同一个。
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Threading;namespace ForTest//check the lock object for thread safety{ class Program { static void Main(string[] args) { son myson = new son(); Parallel.For(0, 5, (int i) => { myson.methodA(); myson.methodC(); }); Console.ReadKey(); } } public class grandfather { //protected static object syncRoot = new object(); } public class father:grandfather { private static object syncRoot = new object(); protected int cont = 0; public virtual bool methodA() { lock (syncRoot) { cont++; Thread.Sleep(1000); Console.WriteLine("cout++ is " + cont); return true; } } public virtual bool methodB() { lock (syncRoot) { return true; } } } public class son:father { private static object syncRoot = new object(); public bool methodC() { lock (syncRoot) { cont += 2; Thread.Sleep(2000); Console.WriteLine("cont += 2 is " + cont); return true; } } }}
输出：
cout++ is 1cout++ is 4cont += 2 is 5cout++ is 5cout++ is 8cont += 2 is 9cout++ is 11cont += 2 is 11cont += 2 is 13cont += 2 is 15
case2：
case1的解决方法是，在父类初始化锁对象，让子类继承。这样就线程安全了。如下。
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Threading;namespace ForTest//check the lock object for thread safety{ class Program { static void Main(string[] args) { son myson = new son(); Parallel.For(0, 5, (int i) => { myson.methodA(); myson.methodC(); }); Console.ReadKey(); } } public class grandfather { protected static object syncRoot = new object(); } public class father:grandfather { protected int cont = 0; public virtual bool methodA() { lock (syncRoot) { cont++; Thread.Sleep(1000); Console.WriteLine("cout++ is " + cont); return true; } } public virtual bool methodB() { lock (syncRoot) { return true; } } } public class son:father { public bool methodC() { lock (syncRoot) { cont += 2; Thread.Sleep(2000); Console.WriteLine("cont += 2 is " + cont); return true; } } }}
输出：
cout++ is 1cout++ is 2cont += 2 is 4cout++ is 5cout++ is 6cout++ is 7cont += 2 is 9cont += 2 is 11cont += 2 is 13cont += 2 is 15
case3：
当然有些特殊情况下，子类硬要重新实例化一个锁对象。如何避免上面第一种线程安全问题发生？需要：
子类加锁重写父类分方法（如果父类methodA是虚方法）
或者
new一下（如果父类methodA是实例方法）。
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Threading;namespace ForTest//check the lock object for thread safety{ class Program { static void Main(string[] args) { son myson = new son(); Parallel.For(0, 5, (int i) => { myson.methodA(); myson.methodC(); }); Console.ReadKey(); } } public class grandfather { protected static object syncRoot = new object(); } public class father:grandfather { protected int cont = 0; public virtual bool methodA() { lock (syncRoot) { cont++; Thread.Sleep(1000); Console.WriteLine("cout++ is " + cont); return true; } } public virtual bool methodB() { lock (syncRoot) { return true; } } } public class son:father { private static object sync = new object(); public override bool methodA()//重写 { lock (sync) { return base.methodA(); } } public bool methodC() { lock (sync) { cont += 2; Thread.Sleep(2000); Console.WriteLine("cont += 2 is " + cont); return true; } } }}
或
public new bool methodA()\new一下 { lock (sync) { return base.methodA(); } }
输出：
cout++ is 1cout++ is 2cont += 2 is 4cout++ is 5cout++ is 6cout++ is 7cont += 2 is 9cont += 2 is 11cont += 2 is 13cont += 2 is 15
以上就是 从0自学C#13–子类和父类方法的锁对象问题的内容，更多相关内容请关注PHP中文网（www.php.cn）！
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