Question

我需要帮助从emailaddresses列表中删除重复项。我需要添加代码以在emailaddresses类中对emailaddresses进行分组。由于电话号码不同，Sql返回重复的电子邮件地址。有什么建议？感谢。

这是我的代码：的 1。类

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    ]),

2。来自sql查询的数据

public class Student
{
    public string StudentId { get; set; }
    public string Gender { get; set; }  
    public List<EmailAddresses> emailAddresses { get; set; }
}

public class EmailAddresses
{
    public string EmailAddress { get; set; }    
}

第3。代码

StudentId   EmailAddresses  IsPreferred Number  TelephoneType                                                                                               
123456789   maryjoe@gmail.com   FALSE   5556565 Present Evening Phone                                                                                               
123456789   maryjoe@gmail.com   FALSE   8885566 Permanent Day Phone                                                                                             
123456789   mary.joe@cuu.edu    TRUE    5556565 Present Evening Phone                                                                                               
123456789   mary.joe@cuu.edu    TRUE    8885566 Permanent Day Phone                                                                                             
456789123   dh@mycollege.edu    TRUE    7513150 Business Day Phone                                                                                              
456789123   donna.hill@cu.edu   TRUE    4123300 Present Day Phone                                                                                               
456789123   donna.hill@cu.edu   FALSE   4123300 Present Day Phone

Answer 1

如果我认为你是正确的，你需要得到不同的值，你可以这样做

 List<Product> list = products
                   .GroupBy(a => a.Code )
                   .Select(g => g.First())
                   .ToList();

或

创建竞争对手，而不是试图找出不同的对象

完整代码的文章：DistinctBy in Linq (Find Distinct object by Property)

    class ProductComparare : IEqualityComparer<product>
    {
        private Func<Product, object> _funcDistinct;
        public ProductComparare(Func<Product, object> funcDistinct)
        {
            this._funcDistinct = funcDistinct;
        }

        public bool Equals(Product x, Product y)
        {
            return _funcDistinct(x).Equals(_funcDistinct(y));
        }

        public int GetHashCode(Product obj)
        {
            return this._funcDistinct(obj).GetHashCode();
        }
    }

var list2 = products.Distinct(new ProductComparare( a => a.Code ));

Answer 2

虽然最好在返回之前过滤掉重复项，但这也会增加代码的复杂性。如果您的结果集很小，那么在您返回数据后进行过滤的内存和CPU开销可能会很容易且清晰地获得您需要的结果。您可以使用自定义IEqualityComparer检查不同的结果，并在包含不同电子邮件地址的每个学生记录上创建新的emailAddresses列表。

public List<Student> GetStudentData()
{
    List<Student> dataStudent;
    using (IDbConnection connection = RepositoryHelper.OpenConnection())
    {
        dataStudent = connection.Query<dynamic>(
            "mystoredprocedure", 
            commandType: CommandType.StoredProcedure)
                .GroupBy(x => x.StudentId)
                .Select(x => new Student 
                    { 
                        StudentId = x.First().StudentId, 
                        Gender = x.First().Gender,
                        emailAddresses = x.Select(ea => new EmailAddresses 
                            { 
                                EmailAddress = ea.emailAddresses 
                            }).ToList()
                    }).ToList();

        dataStudent.ForEach(x => x.emailAddresses = x.emailAddresses
            .Distinct(new StudentEmailEqualityComparer()).ToList());

        return dataStudent;
    }
}

public class StudentEmailEqualityComparer : IEqualityComparer<EmailAddresses>
{

    public bool Equals(EmailAddresses x, EmailAddresses y)
    {
        return x.EmailAddress.Equals(y.EmailAddress);
    }

    public int GetHashCode(EmailAddresses obj)
    {
        return obj.EmailAddress.GetHashCode();
    }
}

Linq - 每个班级

2 个答案: