Remove duplicates from a List(Of T) in VB.NET
.net, generics, vb.net
Solution
You need to implement `GetHashCode1` so that any two equal objects have the same hashcode.
If many unequal objects have the same hashcode, it will perform much more slowly, especially for large lists. In other words, don't change it to `Return 0`.
In your case, the simplest implementation would be like this:
Return StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.EmailAddress) _
Xor StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.GivenName) _
Xor StringComparer.CurrentCultureIgnoreCase.GetHashCode(obj.Surname)
If you want a more robust implementation, see this answer.
Problem
I fail to remove duplicates from my List. What am I doing wrong? ``` Dim Contacts As New List(Of Person) ... ' remove duplicates ' Contacts = Contacts.Distinct(New PersonEqualityComparer).ToList ``` my equality comparer: ``` Public Class PersonEqualityComparer Implements IEqualityComparer(Of Person) Public Function Equals1(ByVal x As Person, ByVal y As Person) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of Person).Equals Return String.Equals(x.EmailAddress, y.EmailAddress, StringComparison.CurrentCultureIgnoreCase) AndAlso _ String.Equals(x.GivenName, y.GivenName, StringComparison.CurrentCultureIgnoreCase) AndAlso _ String.Equals(x.Surname, y.Surname, StringComparison.CurrentCultureIgnoreCase) End Function Public Function GetHashCode1(ByVal obj As Person) As Integer Implements System.Collections.Generic.IEqualityComparer(Of Person).GetHashCode Return obj.GetHashCode End Function End Class ```