check for duplicates

[Peter Kirk]

Hi

if I have a List<MyObject> of MyObject objects, what is the best way to
check for duplicates? (By "duplicate" I mean that MyObject has a property
called "name" for example, which I want to check if this value appears more
than once in the list of MyObjects).

Thanks,
Peter

 

[Peter Kirk]

if I have a List<MyObject> of MyObject objects, what is the best way to
check for duplicates? (By "duplicate" I mean that MyObject has a property
called "name" for example, which I want to check if this value appears
more than once in the list of MyObjects).

Hi again - anyone know of some good web-resources which describe best
practices for overriding Equals and GetHashCode?

Thanks,
Peter

 

[Marc Gravell]

What I would do is create a Dictionary<string, MyObject>, and then something
like (not tested)
Dictionary<string, MyObject> uniqueSet = new Dictionary<string, MyObject>();
foreach(MyObject obj in originalList> {
string name = obj.Name;
if(uniqueSet.ContainsKey(name)) {
// whoops! we have a duplicate (against uniqueSet[name])
} else {
uniqueSet.Add(name, obj);
}
}

Note that if you want to see what it conflicts with, then the following is
more efficient:
MyObject conflict;
if(uniqueSet.TryGetValue(name, out conflict)) {
// conflicts against conflict
} else {
uniqueSet.Add(name, obj);
}

Marc