Writing and calling operator ==

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• A

  abdullah22y agoPosted Nov 14, 2004, 8:51 AM

  Ok......... you know I havn't test this before but I ensist on it.....since I know it in JAVA....not C#........however C# is almost like JAVA...so I asume it's corectness.... Good luck.....
• B

  bilnaad22y agoPosted Nov 14, 2004, 7:53 AM

  Ow sorry, your right. I tested using: Person a = new Person("Rob" ,21); Person b = new Person("Don" ,34); Person c = new Person(a); Person aa = a; Person bb = b; Person cc = c; Console.WriteLine("a is {0}b" ,a == b?"":"not " );//false Console.WriteLine("a is {0}c" ,a == c?"":"not " );//false Console.WriteLine("aa is {0}a" ,aa == a?"":"not " );//false Console.WriteLine("bb is {0}b" ,bb == b?"":"not " );//false Console.WriteLine("cc is {0}c" ,cc == c?"":"not " );//false While a and c have the same values they are different objects thus False ^_^ Whoops, my bad ^_^
• B

  bilnaad22y agoPosted Nov 14, 2004, 7:30 AM

  Both ways had the same results. Both the original == and the overloaded.
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  abdullah22y agoPosted Nov 14, 2004, 5:52 AM

  Hi again... And the results are commented after the Console.WriteLine(). So don't go and say the addresses are compared because both a and b have different addresses and are compared nicely. thats when you use the == operator without overriding it ....... but you chaning its implementation.... public static bool operator==(Person a, object b) { return a.Equals(b); } so......before overriding it....it will behaive as i said....... Good luck.....
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  bilnaad22y agoPosted Nov 13, 2004, 7:55 PM

  Urhmm, maybe I'm missing something^_^ But when I tested the situation the results were just fine for me. I had a Console app with this code. using System; namespace csConsole { class Person { string name; int age; public Person(string name ,int age) { this.name = name; this.age = age; } public string Name { get{return name;} } public int Age { get{return age;} } /* public override int GetHashCode() { return base.GetHashCode (); } public override bool Equals(object obj) { if(obj is Person) { Person pers = (Person)obj; if( (pers.Name == this.name) && (pers.Age == this.age) ) { return true; } } return false; } public static bool operator==(Person a, object b) { return a.Equals(b); } public static bool operator!=(Person a, object b) { return !a.Equals(b); } */ } class Operators { public static void Main() { Person a = new Person("Rob" ,21); Person b = new Person("Don" ,34); Console.WriteLine( a == b );//false Console.WriteLine( a != b );//true a = b; b = null; Console.WriteLine( a == b );//false Console.WriteLine( a != b );//true Console.Read(); } } } And the results are commented after the Console.WriteLine(). So don't go and say the addresses are compared because both a and b have different addresses and are compared nicely.
• A

  abdullah22y agoPosted Nov 13, 2004, 7:26 AM

  Hi...... ofcourse the operator == will return false..... if you have i.e. : Person person1 = new Person("A"); Person person2 = new Person("A"); if(person1==person2)==> false...... since == checkes the memory address not the actual contents.... but if you have : Person person1 = new Person("A"); Person person2 = person1; then == will return true...... since person2 will point to the same address..... to solve it you can write your own method to test i.e. : public bool check(Person p1 , Person p2 ){ if(p1.getName().Equals(p2.getName())) return true ; else return false ; } or you can override the == operator......... Good luck...... }
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  robin 022y agoPosted Nov 13, 2004, 12:02 AM

  Try this way: public static bool operator ==(tstcls o1, tstcls o2) { if (System.Object.ReferenceEquals(o1, null) == true && System.Object.ReferenceEquals(o2, null) == true) { return true;} if (String.Compare(o1.mainstr, o2.mainstr)==0) return true; else return false; } public static bool operator !=(tstcls o1, tstcls o2) { if (System.Object.ReferenceEquals(o1, null) == false && System.Object.ReferenceEquals(o2, null) == false) { return true;} if (String.Compare(o1.mainstr, o2.mainstr)==0) return false; else return true; }
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  Mykonine22y agoPosted Nov 12, 2004, 11:50 PM

  In C++, you could use (person1 == person2), then (&person1 == &person2) In C#, the default == operator checks whether or not they refer to the same object. Overloading it removes that functionality, so instead of using the == operator I suggest using a .Equals method, inherited from the Object.Equals method.