1

我已经使用下面的 linq 查询来加入一些表以获取准确的数据..

(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 中获取不同的记录......

CustomerDetail 可以有多个相同 CustomerId 的记录

请建议我如何过滤我的查询以仅从 CustomerDetail 表中获取不同的记录

谢谢，

4

4 回答 4

5

您可以为您的 CustomerDetail(s)-Objects 实现一个比较器类，然后使用接受您的比较器的重载版本。

像这样的东西：

class CustomerDetailsComparer: IEqualityComparer<CustomerDetail>
{
    public bool Equals(CustomerDetail x, CustomerDetail y)
    {

        if (Object.ReferenceEquals(x, y)) return true;

        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;

        return x.CustomerId == y.CustomerId;
    }


    public int GetHashCode(CustomerDetail cd)  
    {
         // Do something here
    }  
}


// ...

DbContext.CustomerDetails.Distinct(new CustomerDetailsComparer());
于 2012-05-22T05:56:33.063 回答
2

LINQ 提供了Distinct方法。但是，它默认使用默认的相等比较器，或者您指定的一个可选。

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();
   }
}

接着

(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();
于 2012-05-22T05:48:35.657 回答
1

.ToList() 只需在Ie之前使用 .Distinct()

(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 
   {
      CustomerId = row.cpd.CustomerDetail_CustomerID,
      CustomerName = row.c.Customer_LastName+", "+row.c.Customer_FirstName,
   }).Distinct().ToList();
于 2012-05-22T05:48:49.870 回答
0

尝试：

(--your code--).Distinct().ToList();
于 2012-05-22T05:52:56.983 回答