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 1 cout++ is 4 cont += 2 is 5 cout++ is 5 cout++ is 8 cont += 2 is 9 cout++ is 11 cont += 2 is 11 cont += 2 is 13 cont += 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 1 cout++ is 2 cont += 2 is 4 cout++ is 5 cout++ is 6 cout++ is 7 cont += 2 is 9 cont += 2 is 11 cont += 2 is 13 cont += 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 1 cout++ is 2 cont += 2 is 4 cout++ is 5 cout++ is 6 cout++ is 7 cont += 2 is 9 cont += 2 is 11 cont += 2 is 13 cont += 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）！
