c# - 如何在LINQ中获得独特的值(value)

我已经在下面的linq查询中使用了一些表来获取准确的数据。

(from row in
  (from c in DbContext.Customer
   join cd in DbContext.CustomerDetails
   on c.Customer_Id equals cd.CustomerDetail_CustomerId
   join cp in DbContext.ProductPurchases
   on cd.CustomerDetail_OrgID equals cp.ProductPurchase_OrgID
   where cd.CustomerDetail_OrgId == OrganizationID --organization Id is common
   && c.Customer_Org_Id == OrganizationID
   && cp.ProductPurchase_OrgID == OrganizationID
   orderby cd.CustomerDetail_CreatedDate descending
   select new { c, cd, cp })
   select new CustomerDTO
   {
      CustomerId = row.cpd.CustomerDetail_CustomerID,
      CustomerName = row.c.Customer_LastName+", "+row.c.Customer_FirstName,
   }).ToList();

我在CustomerDetail记录中有一个小问题，我只想根据CustomerId从CustomerDetail中获得不同的记录。

CustomerDetail可以为同一CustomerId拥有多个记录

请建议我如何过滤查询以仅从CustomerDetail表中获取不同的记录

谢谢，

最佳答案

LINQ提供了Distinct方法。但是，它默认使用默认的相等比较器，也可以使用您指定的可选比较器。

我建议不要使用匿名类型，而是使用属性CustomerId和CustomerName定义一个类，然后覆盖Equals。

public class DistinctCustomer
{
   public int CustomerId { get; set; }
   public string CustomerName { get; set; }

   public override bool Equals(object obj)
   {
        if (ReferenceEquals(obj, null)) return false;
        if (ReferenceEquals(this, obj)) return true;

        var other = obj as DistinctCustomer;

        if (other == null) return false;

        return CustomerId == other.CustomerId;
   }

   public override int GetHashCode()
   {
        return CustomerId.GetHashCode();
   }
}

然后

(from row in
  (from c in DbContext.Customer
   join cd in DbContext.CustomerDetails
   on c.Customer_Id equals cd.CustomerDetail_CustomerId
   join cp in DbContext.ProductPurchases
   on cd.CustomerDetail_OrgID equals cp.ProductPurchase_OrgID
   where cd.CustomerDetail_OrgId == OrganizationID --organization Id is common
   && c.Customer_Org_Id == OrganizationID
   && cp.ProductPurchase_OrgID == OrganizationID
   orderby cd.CustomerDetail_CreatedDate descending
   select new { c, cd, cp })
   select new DistinctCustomer
   {
      CustomerId = row.cpd.CustomerDetail_CustomerID,
      CustomerName = row.c.Customer_LastName+", "+row.c.Customer_FirstName,
   }).Distinct().ToList();

关于c# - 如何在LINQ中获得独特的值(value)，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/10696316/