Linq to SQL question - specifying columns then modifying column - linq-to-sql

Question

I'm trying to write a linq to sql method that handles sorting, paging, and filtering for an ajax grid. I created a partial class Employee that has a TotalRecordCount, as I need to pass this to the javascript for setting up the pager. The problem is that it won't build because I can't set the AnonymousType#1.TotalRecordCount, it's read-only. Yet if I do "select new Employee", then it will throw the Exception - "Explicit construction of entity type 'InVision.Data.Employee' in query is not allowed.".
Here's the code...
public string GetPageJSON(string sortColumn, string sortDirection, int pageNumber, int pageSize, EmployeeSearch search)
{
var query = from e in db.Employees
select new
{
EmployeeID = e.EmployeeID,
FirstName = e.FirstName,
LastName = e.LastName,
LoginName = e.LoginName,
IsLockedOut = e.IsLockedOut,
TotalRecordCount = e.TotalRecordCount
};
//searching.
if (search.FirstName.Length > 0) query = query.Where(e => e.FirstName.Contains(search.FirstName));
if (search.LastName.Length > 0) query = query.Where(e => e.LastName.Contains(search.LastName));
if (search.LoginName.Length > 0) query = query.Where(e => e.LoginName.Contains(search.LoginName));
if (search.Status.Length > 0) query = query.Where(e => (search.Status == "Active" && !e.IsLockedOut)
|| (search.Status == "Inactive" && e.IsLockedOut));
//sorting.
query = query.OrderBy(sortColumn, sortDirection);
//get total record count.
int totalRecordCount = query.Count();
//paging.
query = query.Skip((pageNumber - 1) * pageSize).Take(pageSize);
//set total record count.
var list = query.ToList();
if (list.Count > 0)
{
list[0].TotalRecordCount = totalRecordCount; //throws exception
}
//return json.
JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Serialize(list);
}

Answer 1

You'll want to select the original objects rather than mapping them to new objects (whether of the same type, or an anonymous type).
Replace this:
var query = from e in db.Employees
select new
{
EmployeeID = e.EmployeeID,
FirstName = e.FirstName,
LastName = e.LastName,
LoginName = e.LoginName,
IsLockedOut = e.IsLockedOut,
TotalRecordCount = e.TotalRecordCount
};
With this:
var query = db.Employees.AsQueryable();
Then later on replace this:
var list = query.ToList();
if (list.Count > 0)
{
list[0].TotalRecordCount = totalRecordCount;
}
With this:
var list = from e in query
select new
{
EmployeeID = e.EmployeeID,
FirstName = e.FirstName,
LastName = e.LastName,
LoginName = e.LoginName,
IsActive = !e.IsLockedOut,
TotalRecordCount = totalRecordCount
};
I think that should be everything. If the JavaScriptSerializer requires a List, just make sure you use it like this: return serializer.Serialize(list.ToList());

Answer 2

I ended up using a custom view class to get this to work...
partial class EmployeeView
{
public int EmployeeID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string LoginName { get; set; }
public bool IsActive { get; set; }
public int TotalRecordCount { get; set; }
}
public string GetPageJSON(string sortColumn, string sortDirection, int pageNumber, int pageSize, EmployeeSearch search)
{
var query = from e in db.Employees
select new EmployeeView
{
EmployeeID = e.EmployeeID,
FirstName = e.FirstName,
LastName = e.LastName,
LoginName = e.LoginName,
IsActive = !e.IsLockedOut,
TotalRecordCount = 0
};
//searching.
if (search.FirstName.Length > 0) query = query.Where(e => e.FirstName.Contains(search.FirstName));
if (search.LastName.Length > 0) query = query.Where(e => e.LastName.Contains(search.LastName));
if (search.LoginName.Length > 0) query = query.Where(e => e.LoginName.Contains(search.LoginName));
if (search.Status.Length > 0) query = query.Where(e => (search.Status == "Active" && e.IsActive)
|| (search.Status == "Inactive" && !e.IsActive));
//sorting.
query = query.OrderBy(sortColumn, sortDirection);
//get total record count.
int totalRecordCount = query.Count();
//paging.
query = query.Skip((pageNumber - 1) * pageSize).Take(pageSize);
//set total record count.
var list = query.ToList();
if (list.Count > 0)
{
list[0].TotalRecordCount = totalRecordCount;
}
//return json.
JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Serialize(list);
}