Get Total Count and Page Rows in same database trip when using Entity Framework

问题

I am currently using the following method to get a page of customers as well as the total count. The only problem is that I am making 2 database trips - one for getting the total count and the other for getting the actual rows for the page.

My question is: Can I combine the totalcount query with the actual rows query so Entity Framework sends both the queries in a single database trip?

public IList GetPageOfCustomers(string name, int skipCount, 
                     int pageSize, out int totalCount) {

using(CustomerEntities e = new CustomerEntities()) {

    //FIRST QUERY
    var query = (from c in e.Customers
    where c.NAME.Contains(name)
    select new {
        c.CustomerID, c.NAME, c.CITY, c.STATE, c.COUNTRY
    })
        .Distinct()
        .OrderBy(s = > s.NAME)
        .ThenBy(s = > s.CITY)
        .ThenBy(s = > s.CustomerID);


    //SECOND QUERY ( executed in a separate database trip)
    int totalCount = (from c in e.Customers
    where c.NAME.Contains(name)
    select new {
        c.CustomerID, c.NAME, c.CITY, c.STATE, c.COUNTRY
    })
        .Distinct()
        .Count();

    return query.Skip(skipCount).Take(pageSize).ToList();
     }//END of  USING
   }//END of  METHOD

回答1:

Depending on the cost of the database roundtrip and number of items coming back, it might be faster/easier to perform the base query once and do the paging/count operations on the c# server. i.e.

var results = (from c in e.Customers
               where m.Name.Contains(name)
               select new { c.CustomerId, c.NAME, c.CITY, c.STATE, c.COUNTRY })
              .Distinct()
              .OrderBy(s => s.NAME)
              .ThenBy(s => s.CITY)
              .ThenBy(s => s.CustomerId)
              .ToList();
totalCount = results.Count;
return results.Skip(skipCount).Take(pageSize).ToList();

This will only perform one database call, but won't perform the paging operations on the sql server.

Edit:
Also take a look at this Better way to query a page of data and get total count in entity framework 4.1?

回答2:

I thought and research a lot on this issue. Right now and with EF 6, there are 2 good practices:

(1) The first solution is to have a Stored Procedure (I know, I Know, you usually want to avoid Stored Procedures when you work with EF, go to solution 2 then!), which returns multiple results. This article explained it:

Entity Framework Sprocs with Multiple Result Sets

(2) The second best practice is to use "Query Future" feature of Entity Framework Plus package. This is a very cool extension to Entity Framework and can run multiple queries in one database trip.

来源：https://stackoverflow.com/questions/24221749/get-total-count-and-page-rows-in-same-database-trip-when-using-entity-framework

标签

entity-framework-4