class A
{
public override int GetHashCode()
{
return 1;
}
}
class B : A
{
public override int GetHashCode()
{
return ((object)this).GetHashCode();
}
}
new B().GetHashCode()
this overflows the stack. How can I call Object.GetHashCode() from B.GetHashCode()?
edit: B now inherits from A.
(edit - misread question)
If you want to get the original object.GetHashCode() version; you can't - at least, not unless A makes it available via something like:
protected int GetBaseHashCode() { return base.GetHashCode();}
(and have B call GetBaseHashCode()).
The reason it overflows is that GetHashCode is (obviously) virtual - it doesn't matter if you cast it to object; it still starts at the most-derived implementation in the actual object, i.e. B.GetHashCode() (hence the explosion).
DynamicMethod. Something like Dogett's answer to a similar question
You can use RuntimeHelpers.GetHashCode(object) to get the original hash code of the object:
class A
{
public override int GetHashCode()
{
Console.WriteLine("base hashcode is: " + base.GetHashCode());
return 1;
}
}
class Program
{
public static void Main(string[] args)
{
A a = new A();
Console.WriteLine("A's hashcode: " + a.GetHashCode());
Console.WriteLine("A's original hashcode: " + RuntimeHelpers.GetHashCode(a));
}
}
This produces the following result:
base hashcode is: 54267293
A's hashcode: 1
A's original hashcode: 54267293
If you take a look at RuntimeHelpers.GetHashCode(object) in Reflector, you'll see that it calls the internal static method object.InternalGetHashCode(object). If you'd like to know more, have a look at this question regarding the default implementation of GetHashCode.
I'm using an external library and I wanted to call the base.base also (because of a bug in certain case). After some research I came across this page http://www.rsdn.ru/forum/dotnet/475911.aspx
It's quite simple: You define a delegate using the base class you want to call your method and set the object pointer to *this (or the object you want)
So, the important code is:
public delegate void MD();
public void Test() {
// A is the base class you want to call the method.
A a = new A();
// Create your delegate using the method name "M" with the instance 'a' of the base class
MD am = (MD)Delegate.CreateDelegate(typeof(MD), a, "M");
// Get the target of the delegate and set it to your object (this in most case)
am.GetType().BaseType.BaseType.GetField("_target", BindingFlags.Instance BindingFlags.NonPublic).SetValue(am, this);
// call the method using the delegate.
am();
}
If you can modify the code of the sub-sub class then you can implement the functionality of the sub-sub-method with a static method. This static (public) method has as first parameter an object of the class. That way you can call it from everywhere.
class A
{
public static int CalcHashCode(A obj)
{
return 1;
}
public override int GetHashCode()
{
return CalcHashCode(this);
}
}
class B : A
{
public override int GetHashCode()
{
return A.CalcHashCode(this);
}
}
