returning total count of records

问题

I am using WCF rest service and i want to return total record count just as we have inlinecount in webapi or breeze.

My method in WCF is

   [WebGet(UriTemplate = "GiveMeNamesOfStudents", ResponseFormat = WebMessageFormat.Json)]
    public List<MyDataClass> GiveMeNamesOfStudentsList()
    {
        var returnData = (from myentity in myEntityRepository.AsQueryable()
                          select new MyDataClass
                            {
                                Id = myentity.Id,
                                Name = myentity.Name
                            }).Skip(PageSize * PageNo).Take(PageSize).ToList();
        return returnData;
    }

How can i return total record count of my actual data together with data?

回答1:

I suggest to return a DTO containing your list and the total count.

You can add other informations like the page count for example but i will keep it simple here.

First create your generic DTO so you can use it in other methods too.

 public class ListResult<T>
 {
     public List<T> Data { get; set; }
     public int TotalCount { get; set; }
     public int Page{ get; set; }
 }

Now return the object

[WebGet(UriTemplate = "GiveMeNamesOfStudents", ResponseFormat = WebMessageFormat.Json)]
public ListResult<MyDataClass> GiveMeNamesOfStudentsList()
{
    var returnData = (from myentity in myEntityRepository.AsQueryable()
                      select new MyDataClass
                        {
                            Id = myentity.Id,
                            Name = myentity.Name
                        }).Skip(PageSize * PageNo).Take(PageSize).ToList();

    return new ListResult<MyDataClass> 
                        { 
                             Data = returnData, 
                             TotalCount = myEntityRepository.Count(), 
                             Page = PageNo 
                        };
}

回答2:

You have to do query the DB twice; once without .Skip.Take, to get the total count, then run the same query again with .Skip.Take to get the page of data.

    var returnData = (from myentity in myEntityRepository.AsQueryable()
                      select new MyDataClass
                        {
                            Id = myentity.Id,
                            Name = myentity.Name
                        }).Skip(PageSize * PageNo).Take(PageSize).ToList();

    var totalCount = myEntityRepository.myentity.count();

---

Another alternative may be to not use EF, and instead just call a stored procedure that could run both queries and return both values in output parameters. This would still run 2 queries, but would only use 1 call frm your app to the DB instead of 2.

回答3:

Because your method's return type is List<MyDataClass>, you can't return anything else. You'll need to introduce a DTO that returns your entities along with the count:

public class MyDataClassDTO
{
    public List<MyDataClass> Data { get; set; }
    public int TotalRecordCount { get; set; }   
}

And return that.

来源：https://stackoverflow.com/questions/26779263/returning-total-count-of-records