Question

i have used below linq query to join some table to get accurate data..

(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();

i have a small problem in CustomerDetail records i only want to get distinct records from the CustomerDetail based on the CustomerId….

CustomerDetail can have more than one records for the same CustomerId

please suggest how i can filter my query to get only distinct records from the CustomerDetail table

thanks,

Answer 1

LINQ provides the Distinct method. However, it uses the default equality comparer by default, or optionally one you specified.

I would recommend instead of using an anonymous type, define a class with the properties CustomerId and CustomerName, then override 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();
   }
}

and then

(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();