C#重载操作符“==”执行时引发“Process is terminated due to StackOverflowException.”的解决办法

昨天编程重载“==”时，例程如下：

public class DeviceInfo
{
public override bool Equals(object obj)
{
return this.Device == ((DeviceInfo)obj).Device;
}

public static bool operator ==(DeviceInfo obj1, DeviceInfo obj2)
{
if (obj1 == null) return obj2 == null;

return obj1.Device == obj2.Device;
}

public static bool operator !=(DeviceInfo obj1, DeviceInfo obj2)
{
return !(obj1==obj2);
}

public string Device;//设备名称，关键字
public string IP;//IP地址
//...
}

编译无任何问题，但执行时却抛出“Process is terminated due to StackOverflowException.”，经分析，是由于对象为空时，“==”就形成了无结束的递归调用，直至最终堆栈溢出。要解决此问题，必须打破无休止的递归调用，通过调用基类的操作符来解决该问题。

public class DeviceInfo
{
public override bool Equals(object obj)
{
if(! (obj is DeviceInfo)) return false;

DeviceInfo di2 = (DeviceInfo)obj;
return (this.Device.CompareTo(di2.Device)==0);
}

public static bool operator ==(DeviceInfo obj1, DeviceInfo obj2)
{
if ((obj1  as object) == null) return (obj2 as object) == null;//引用基类object的比较操作符

return obj1.Equals(obj2);
}

public static bool operator !=(DeviceInfo obj1, DeviceInfo obj2)
{
return !(obj1==obj2);
}

public string Device;//设备名称，关键字
public string IP;//IP地址
//...
}

编译环境：VS2010（C#）