CODEWITHSUNDEEP
c#
Patrik
Patrik

Reputation: 1129

Compare two lists with Except method

I'm trying to compare two lists with the Except method but it doesn't work correct:

List<Customer> PotentialSharedCustomer = new List<Customer>();
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "01234", Name = "Hans Jürgen" });
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "05465", Name = "Beate Müller" });
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "15645", Name = "Sabine Meyer" });
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "54654", Name = "Moritz Kummerfeld" });
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "15647", Name = "Hanna Testname" });

List<Customer> ActualSharedCustomer = new List<Customer>();
ActualSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "01234", Name = "Hans Jürgen" });
ActualSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "05465", Name = "Beate Müller" });
ActualSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "15645", Name = "Sabine Meyer" });

PrepareCreateSharedCustomer(PotentialSharedCustomer, ActualSharedCustomer);

public void PrepareCreateSharedCustomer(List<Customer> potentialSharedCustomer, List<Customer> actualSharedCustomer)
{
    List<Customer> result = potentialSharedCustomer.Except(actualSharedCustomer).ToList<Customer>();
}

The result of the variable "result" should be all records of "PotentialSharedCustomers", there are not in the list "ActialSharedCustomer":

PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "54654", Name = "Moritz Kummerfeld" });
PotentialSharedCustomer.Add(new Customer { AccountId = Guid.Empty, AccountNumber = "15647", Name = "Hanna Testname" });

I thougt "Except" is the correct way to solve this, but I get the return of all items of "PotentialSharedCustomer"

Thx for help

Upvotes: 7

Views: 12906

Answers (3)

Manjur Gani
Manjur Gani

Reputation: 21

var distinctCustomer = PotentialSharedCustomer
    .Select(p => p.AccountNumber)
    .Except(actualSharedCustomer.Select(q => q.AccountNumber))
    .ToList();

Upvotes: 1

tmadsen
tmadsen

Reputation: 951

Customer should implement IEquatable<Customer>, which means you must implement public bool Equals(Customer other) (that return true, if other is equal to this), and public int GetHashCode().

Check out the documentation for examples: http://msdn.microsoft.com/en-us/library/bb300779.aspx

There's also this other StackOverflow answer that exemplifies how to make a GetHashCode() implementation: https://stackoverflow.com/a/263416/62802.

Upvotes: 2

D Stanley
D Stanley

Reputation: 152566

One way without overriding Equals or writing a custom IEqualityComparer is to get a list of identifiers and then filter your list:

List<string> accountNumbers = 
    potentialSharedCustomer.Select(c => c.AccountNumber)
                           .Except(actualSharedCustomer.Select(c => c.AccountNumber));

List<Customer> result = potentialSharedCustomer.Where(c => accountNumbers.Contains(c.AccountNumber));

You could look at other data structures like HashSet to improve the lookup performance but if the size is small this may be sufficient.

Upvotes: 10

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