public override bool Equals(object obj)
{
if (obj is HashCodeExampleWorking)
{
if (obj.GetHashCode() != this.GetHashCode())
{
return(false);
}
// todo
// 1. comparing element by element // hard work, not universal
HashCodeExampleWorking toTest = obj as HashCodeExampleWorking;
if (toTest.val == this.val)
{
if (toTest.buf == this.buf)
{
return(true);
}
}
// or
// 2. comparing with reflection // comparing Database-Connections, slow
// or
// 3. comparing the results of ToString()
// what if not overridden or should this standard practice
// like GetHashCode and Equals
}
return(false);
}
void TestNotConflicting()
{
String s1 = "Hello";
String s2 = "World";
int x1 = 17 * 17 + s1.GetHashCode();
int x2 = 17 * 17 + s2.GetHashCode();
HashCodeExampleWorking h1 = new HashCodeExampleWorking(x2 * 37, s1);
HashCodeExampleWorking h2 = new HashCodeExampleWorking(x1 * 37, s2);
Hashtable ht = new Hashtable();
ht.Add(h1, null);
ht.Add(h2, null);
}
void TestHashcode()
{
String s1 = "Hello";
String s2 = "World";
// calculating hashcode according to HashCodeAutomater
// to find the collison
Console.WriteLine("s1 (" + s1.GetHashCode() + ")");
Console.WriteLine("s2 (" + s2.GetHashCode() + ")");
int x1 = 17 * 17 + s1.GetHashCode();
int x2 = 17 * 17 + s2.GetHashCode();
HashCodeExampleWorking h1 = new HashCodeExampleWorking(0, s1);
HashCodeExampleWorking h2 = new HashCodeExampleWorking(x1 * 37 - x2 * 37, s2);
Console.WriteLine("HashCode " + h1.GetHashCode() + " Object " + h1);
Console.WriteLine("HashCode " + h2.GetHashCode() + " Object " + h2);
Console.WriteLine(h1 + (h1.Equals(h2) ? "==" : "!=") + h2);
// 2nd collison pair
h1 = new HashCodeExampleWorking(x2 * 37, s1);
h2 = new HashCodeExampleWorking(x1 * 37, s2);
Console.WriteLine("HashCode " + h1.GetHashCode() + " Object " + h1);
Console.WriteLine("HashCode " + h2.GetHashCode() + " Object " + h2);
Console.WriteLine(h1 + (h1.Equals(h2) ? "==" : "!=") + h2);
try {
System.Collections.Hashtable ht = new System.Collections.Hashtable();
ht.Add(h1, null);
ht.Add(h2, null);
}
catch (System.Exception ex) {
Console.WriteLine("Ex (" + ex.ToString() + ")");
if (!h1.Equals(h2))
{
throw new Exception("Ouch, same hashcode different state", ex);
}
}
}
