private static IQueryable <T> Filter <T>(IQueryable <T> queryable, CustomFilter filter)
{
if (filter != null && filter.Logic != null)
{
// Collect a flat list of all filters
var filters = filter.All();
// Get all filter values as array (needed by the Where method of Dynamic Linq)
var values = filters.Select(f => f.Value).ToArray();
// Create a predicate expression e.g. Field1 = @0 And Field2 > @1
string predicate = filter.ToExpression(filters);
// Use the Where method of Dynamic Linq to filter the data
queryable = queryable.Where(predicate, values);
}
return(queryable);
}
public ActionResult Read(int take, int skip, IEnumerable<Sort> sort, CustomFilter filter)
{
using (var northwind = new NorthwindEntities())
{
var result = northwind.Products
.OrderBy(p => p.ProductID) // EF requires ordered IQueryable in order to do paging
// Use a view model to avoid serializing internal Entity Framework properties as JSON
.Select(p => new ProductViewModel
{
ProductID = p.ProductID,
ProductName = p.ProductName,
UnitPrice = p.UnitPrice,
UnitsInStock = p.UnitsInStock,
Discontinued = p.Discontinued
})
.ToDataSourceResult(take, skip, sort, filter);
return Json(result);
}
}
/// <summary>
/// Applies data processing (paging, sorting and filtering) over IQueryable using Dynamic Linq.
/// </summary>
/// <typeparam name="T">The type of the IQueryable</typeparam>
/// <param name="queryable">The IQueryable which should be processed.</param>
/// <param name="take">Specifies how many items to take. Configurable via the pageSize setting of the Kendo DataSource.</param>
/// <param name="skip">Specifies how many items to skip.</param>
/// <param name="sort">Specifies the current sort order.</param>
/// <param name="filter">Specifies the current filter.</param>
/// <returns>A DataSourceResult object populated from the processed IQueryable.</returns>
public static DataSourceResult ToDataSourceResult <T>(this IQueryable <T> queryable, int take, int skip, IEnumerable <Sort> sort, CustomFilter filter)
{
// Filter the data first
queryable = Filter(queryable, filter);
// Calculate the total number of records (needed for paging)
var total = queryable.Count();
// Sort the data
queryable = Sort(queryable, sort);
// Finally page the data
queryable = Page(queryable, take, skip);
return(new DataSourceResult
{
Data = queryable.ToList(),
Total = total
});
}