Question

我正在尝试使用Except方法比较两个列表，但它不正确：

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>();
}

变量“result”的结果应该是“PotentialSharedCustomers”的所有记录，列表中没有“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" });

我认为“除了”是解决这个问题的正确方法，但我得到了“PotentialSharedCustomer”所有项目的回报

寻求帮助

Answer 1

不覆盖Equals或撰写自定义IEqualityComparer的一种方法是获取标识符列表，然后过滤您的列表：

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

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

您可以查看其他数据结构（如HashSet）以提高查找性能，但如果大小很小，则可能就足够了。

Answer 2

Customer应该实施IEquatable<Customer>，这意味着您必须实施public bool Equals(Customer other)（如果other等于this则返回true）和{{ 1}}。

查看文档以获取示例：http://msdn.microsoft.com/en-us/library/bb300779.aspx

还有另一个StackOverflow答案，它说明了如何实现public int GetHashCode()：https://stackoverflow.com/a/263416/62802。

Answer 3

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

使用Except方法比较两个列表

3 个答案: