EF core paging. Select total count in same query - entity-framework-core

Question

I have paging and i want to select count in the same query using simple sql (EF7):
var selectSql = " SELECT TotalCount = COUNT(*) OVER(), E.* FROM [table] E ...";
var rows = context.Set<EventTable>().FromSql<EventTable>(selectSql, parameters.Select(p => p.Value).ToArray()).ToArray();
This select works, but i don't have TotalCount property in my EventTable class, because i don't want that property in database.
I try get TotalCount property from entity tracker:
var row = rows.First();
var entity = context.Entry(row);
var totalCount = entity.Property<int>("TotalCount").CurrentValue;
But then i get error:
The property 'TotalCount' on entity type 'EventTable' could not be found. Ensure that the property exists and has been included in the model.
Then i try to add property in model like this:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<EventTable>(b => b.Property<int>("TotalCount"));
}
It works fine when i want to select, but it throws an exception on insert, because column in database not exist.
And EF will add that column on migration. But i notice, that if before migration generation i add line b.Property("TotalCount"); into ModelSnapshot class it will avoid to add property on migration. But problem on insert still exist.
I try to create another class:
[NotMapped]
public class EventSearchTable : EventTable
{
[Column("total_count")]
[Required]
public int TotalCount { get; set; }
}
and then do this:
var rows = context.Set<EventSearchTable>().FromSql<EventSearchTable>(..);
It works on EF6, but not on EF7, i got error: Value cannot be null.
Parameter name: entityType Because no entity in my DbContext. If i will add EventSearchTable class on my DbContext then it will expect columns like discriminator and etc and will create table in migrations.
Any ideas how to get property TotalCount ?

Answer 1

The following query will get the count and page results in one trip to the database
var query = context.Set<EventTable>();
var page = query.OrderBy(e => e.Id)
.Select(e => e)
.Skip(100).Take(100)
.GroupBy(e => new { Total = query.Count() })
.FirstOrDefault();
if (page != null)
{
int total = page.Key.Total;
List<EventTable> events = page.Select(e => e).ToList();
}