c# - 使用 linq lambda 从具有多个链接表的数据集中填充 C# 类

Question

我正在尝试从 DataSet 填充 C# 类 (contractor) 的列表 (lstContractor)，其中包含字段和列表> 从 SQL 返回。 DataSet 返回多个表，由一个 id 链接。

除 1 个字段外，我已经设法使它全部正常工作，这是我需要从它所在的表中获取的唯一字段。当我尝试使用 LINQ 选择它时，我得到 System. Data.EnumerableRowCollection1[System.String]` 而不是字段的内容。

我的代码如下所示:

    lstContractor = dsContractor.Tables[0].AsEnumerable().Select(contractor => new Contractor
    {
        intContractorId = contractor.Field<int>("ID"),
        strFirstName = contractor.Field<string>("FirstName"),
        strLastName = contractor.Field<string>("LastName"),
        strProfile = dsContractor.Tables[7].AsEnumerable().Where(profile => profile.Field<int>("ContractorId") == contractor.Field<int>("Id")).
            Select(profile => profile.Field<string>("ContractorProfile")).ToString(),
        // populate addresses
        Address = dsContractor.Tables[6].AsEnumerable().Where(address => address.Field<int>("ContractorId") == contractor.Field<int>("Id")).
                Select(address => new Address
                {
                    intId = address.Field<int>("ContractorId"),
                    strAddressLine1 = address.Field<string>("AddressLine1"),
                    strAddressLine2 = address.Field<string>("AddressLine2"),
                    strAddressLine3 = address.Field<string>("AddressLine3"),
                    strAddressLine4 = address.Field<string>("AddressLine4"),
                    strAddressLine5 = address.Field<string>("AddressLine5"),
                    strPostCode = address.Field<string>("PostCode")
                }).ToList<Address>(),

        // populate industries
        Industry = dsContractor.Tables[1].AsEnumerable().Where(Industry => Industry.Field<int>("ContractorId") == contractor.Field<int>("Id")).
            Select(target => new Industry
            {
                intId = target.Field<int>("ContractorId"),
                strIndustryName = target.Field<string>("IndustryName")
            }).ToList<Industry>(),

        // populate key skills
        KeySkill = dsContractor.Tables[2].AsEnumerable().Where(KeySkill => KeySkill.Field<int>("ContractorId") == contractor.Field<int>("Id")).
            Select(target => new KeySkill
            {
                intId = target.Field<int>("ContractorId"),
                strKeySkillName = target.Field<string>("KeySkillName")
            }).ToList<KeySkill>(),

        // populate email addresses
        EmailAddress = dsContractor.Tables[3].AsEnumerable().Where(EmailAddress => EmailAddress.Field<int>("ContractorId") == contractor.Field<int>("Id")).
            Select(target => new EmailAddress
            {
                intId = target.Field<int>("ContractorId"),
                strEmailAddress = target.Field<string>("EmailAddress"),
                strEmailType = target.Field<string>("EmailType")
            }).ToList<EmailAddress>(),

        // populate phone numbers
        PhoneNumber = dsContractor.Tables[4].AsEnumerable().Where(PhoneNumber => PhoneNumber.Field<int>("ContractorId") == contractor.Field<int>("Id")).
            Select(target => new PhoneNumber
            {
                intId = target.Field<int>("ContractorId"),
                strPhoneNumberType = target.Field<string>("PhoneType"),
                strPhoneNumber = target.Field<string>("PhoneNumber")
            }).ToList<PhoneNumber>(),

        Geography = dsContractor.Tables[5].AsEnumerable().Where(PhoneNumber => PhoneNumber.Field<int>("ContractorId") == contractor.Field<int>("Id")).
                Select(target => new Geography
                {
                    intId = target.Field<int>("ContractorId"),
                    strGeography = target.Field<string>("GeographyName")
                }).ToList<Geography>(),


    }).ToList<Contractor>();

这个类看起来像这样:

    public int intContractorId;
public string strFirstName;
public string strMiddleName;
public string strLastName;
public string strDescription; 
public DateTime dtDOB;
public string strGender;
public string strProfile;
public int intIsFullTime;
public int intWorkMonday;
public int intWorkTuesday;
public int intWorkWednesday;
public int intWorkThursday;
public int intWorkFriday;
public int intWorkSaturday;
public int intWorkSunday;
public DateTime dtAvailableFrom;
public int intActive;
public decimal dcSubscrptionCost;
public DateTime dtRenewalDate;
public List<Address> Address;
public List<EmailAddress> EmailAddress;
public List<PhoneNumber> PhoneNumber;
public List<KeySkill> KeySkill;
public List<Geography> Geography;
public List<Industry> Industry;
public List<SubIndustry> SubIndustry;

有问题的字段是 strProfile，但我终究无法弄清楚为什么我得到的是我现在的内容，而不是该字段包含的字符串。

我已经在 Debug模式下检查过，正确的数据在 DataSet 中。

如果我遗漏了什么，请告诉我。

谢谢

Answer 1

这部分:

...Select(profile => profile.Field<string>("ContractorProfile")).ToString()

Linq 的 Select() 返回一个 IEnumerable，因此 ToString() 只是试图告诉您它是一个 IEnumerable。如果您想要返回集合中的第一项，请使用 First() 或 FirstOrDefault():

...Select(profile => profile.Field<string>("ContractorProfile")).First().ToString()