linq到实体的内部联接

本文关键字：内部 实体 linq | 更新日期: 2023-09-27 17:57:54

我有一个名为Customer的实体，它有三个属性：

public class Customer {
    public virtual Guid CompanyId;
    public virtual long Id;
    public virtual string Name;
}

我还有一个名为拆分的实体，它有三个属性：

public class Splitting {
    public virtual long CustomerId;
    public virtual long Id;
    public virtual string Name;
}

现在我需要编写一个获取companyId和customerId的方法。该方法应返回与companyId中的特定customerId相关的拆分列表。类似这样的东西：

public IList<Splitting> get(Guid companyId, long customrId) {    
    var res=from s in Splitting 
            from c in Customer 
            ...... how to continue?
    return res.ToList();
}

linq到实体的内部联接

var res = from s in Splitting 
          join c in Customer on s.CustomerId equals c.Id
         where c.Id == customrId
            && c.CompanyId == companyId
        select s;

使用Extension methods:

var res = Splitting.Join(Customer,
                 s => s.CustomerId,
                 c => c.Id,
                 (s, c) => new { s, c })
           .Where(sc => sc.c.Id == userId && sc.c.CompanyId == companId)
           .Select(sc => sc.s);

您可以在visualstudio中找到一大堆Linq示例。只需选择Help -> Samples，然后解压缩Linq示例。

打开linq samples解决方案并打开SampleQueries项目的LinqSamples.cs。

你正在寻找的答案是在方法Linq14:

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var pairs =
   from a in numbersA
   from b in numbersB
   where a < b
   select new {a, b};

不能100%确定这两个实体之间的关系，但以下是：

IList<Splitting> res = (from s in [data source]
                        where s.Customer.CompanyID == [companyID] &&
                              s.CustomerID == [customerID]
                        select s).ToList();
IList<Splitting> res = [data source].Splittings.Where(
                           x => x.Customer.CompanyID == [companyID] &&
                                x.CustomerID == [customerID]).ToList();

public IList<Splitting> get(Guid companyId, long customrId) {    
    var res=from c in Customers_data_source
            where c.CustomerId = customrId && c.CompanyID == companyId
            from s in Splittings_data_srouce
            where s.CustomerID = c.CustomerID
            select s;
    return res.ToList();
}
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