Why it produces additional SQL queries when use AutoMapper even though all data have been retrieved from database? - sql

Question

I'm using LINQ and AutoMapper in my ASP.NET web project to retrieve data from database. Here is my controller action to retrieve and list all data from database:
public ActionResult ListPlans()
{
db.Database.Log = (log) => System.Diagnostics.Debug.WriteLine(log);
var listPlan = db.Plans?.OrderByDescending(p => p.PlanId).ToList();
var listPlanViewModels = Mapper.Map<IEnumerable<PlanViewModel>>(listPlan);
return View(listPlanViewModels);
}
When I debug it step by step with Visual Studio, I noticed all data from database have been retrieved and put into memory after this line below was executed:
var listPlan = db.Plans?.OrderByDescending(p => p.PlanId).ToList();
Here is the SQL query produced by above line:
SELECT
[Extent1].[PlanId] AS [PlanId],
[Extent1].[PlanName] AS [PlanName],
[Extent1].[PlanStatus] AS [PlanStatus],
[Extent1].[TemplateId] AS [TemplateId],
FROM
[dbo].[Plan] AS [Extent1]
ORDER BY
[Extent1].[PlanId] DESC
But I noticed it produces additional SQL queries to database when executed this line below:
var listPlanViewModels = Mapper.Map<IEnumerable<PlanViewModel>>(listPlan);
It produces SQL query for each row of data in database, the SQL query shows below:
SELECT
[Extent1].[TemplateId] AS [TemplateId],
[Extent1].[Name] AS [Name],
[Extent1].[Description] AS [Description],
[Extent1].[IsActive] AS [IsActive],
FROM
[dbo].[Template] AS [Extent1]
WHERE
[Extent1].[TemplateId] = #EntityKeyValue1
My question is: why does it produce additional SQL queries even though all data in my database table have been retrieved and put into memory?
How to avoid these additional SQL query when using AutoMapper? It caused performance issue because of these additional queries.
Thanks in advance.
Here are my model and view model:
public partial class Plan
{
public int PlanId { get; set; }
public string PlanName { get; set; }
public string PlanStatus { get; set; }
public System.Guid TemplateId { get; set; }
public virtual Template Template { get; set; }
}
public class PlanViewModel
{
[DisplayName("Plan ID")]
public int PlanId { get; set; }
[DisplayName("Name")]
public string PlanName { get; set; }
public Guid TemplateId { get; set; }
[DisplayName("Template")]
public string TemplateName { get; set; }
[DisplayName("Status")]
public string PlanStatus { get; set; }
}