问题
I am using jQuery datatable (http://www.datatables.net) in my MVC4 app and as you may know this table allows server side processing. I am going to use the table in multiple views tied to multiple controllers so I'd like to implement a generic way to filer, sort and page data without the need to write a method for each controller. If I were to do that, they would all look the same but they would target a different entity from the database and be doing textual filtering and sorting on different columns. Here what I have to do today:
public virtual ActionResult AjaxHandler(jQueryDataTableParamModel param)
{
var myProducts = _productRepository.Products;
IEnumerable<Product> filteredProducts = myProducts;
// Filtering
if (!string.IsNullOrEmpty(param.sSearch))
{
var searchTermLower = param.sSearch.Trim().ToLower();
filteredProducts = filteredProducts
.Where(c => c.Title.Contains(param.sSearch)
||
c.Manufacturer.ManufacturerName.ToLower().Contains(searchTermLower)
||
c.Category.CategoryTitle.ToLower().Contains(searchTermLower)
||
c.Size.Title.ToLower().Contains(searchTermLower)
||
c.Price.ToString("C").Contains(searchTermLower));
}
// Sorting
var sortColumnIndex = Convert.ToInt32(Request["iSortCol_0"]);
var sortDirection = Request["sSortDir_0"];
if (sortColumnIndex == 0)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.CreatedDate) : filteredProducts.OrderByDescending(x => x.CreatedDate);
}
else if (sortColumnIndex == 1)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.Title) : filteredProducts.OrderByDescending(x => x.Title);
}
else if (sortColumnIndex == 2)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.Manufacturer.ManufacturerName) : filteredProducts.OrderByDescending(x => x.Manufacturer.ManufacturerName);
}
else if (sortColumnIndex == 3)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.Size.Title) : filteredProducts.OrderByDescending(x => x.Size.Title);
}
else if (sortColumnIndex == 4)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.Category.CategoryTitle) : filteredProducts.OrderByDescending(x => x.Category.CategoryTitle);
}
else if (sortColumnIndex == 4)
{
filteredProducts = sortDirection == "asc" ? filteredProducts.OrderBy(x => x.Price) : filteredProducts.OrderByDescending(x => x.Price);
}
// Paging
var displayedProducts = filteredProducts.Skip(param.iDisplayStart).Take(param.iDisplayLength);
var result = from c in displayedProducts
select new[] { c.ProductId.ToString(CultureInfo.InvariantCulture), c.CreatedDate.ToString("G"), c.Title, c.Manufacturer.ManufacturerName, c.Size.Title, c.Category.CategoryTitle, c.Price.ToString("C") };
return Json(new
{
sEcho = param.sEcho,
iTotalRecords = myProducts.Count(),
iTotalDisplayRecords = filteredProducts.Count(),
aaData = result
}, JsonRequestBehavior.AllowGet);
}
I tried several things to make this generic none of which worked completely - some because of the fact that I filter on all columns and others for other reasons. I am hoping there is a better way to do this so I can just pass columns or functions that select columns instead and have it work.
回答1:
Having just recently dealt with this issue I can tell you that you want to implement dynamic linq in your project. Dynamic linq allows you to write queries such as
results.OrderBy( "id desc" )
and
results.Where( "Name.Contains( 'foo' )" )
Hope these help:
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx http://codefucius.blogspot.com/2012/11/implementing-jqgrid-search.html
Note - I used jqGrid, but the idea remains the same
回答2:
Dynamic SortingAndPagingHelper extension method
/// <summary>
/// Extension method for sorting and filtering
/// </summary>
public static class SortingAndPagingHelper
{
public static IEnumerable<TSource> SortingAndPaging<TSource>(this IEnumerable<TSource> source, SortingAndPagingInfo sortingModal)
{
// Gets the coloumn name that sorting to be done on
PropertyInfo propertyInfo = source.GetType().GetGenericArguments()[0].GetProperty(sortingModal.SortColumnName);
// sorts by ascending if sort criteria is Ascending otherwise sorts descending
return sortingModal.SortOrder == "Ascending" ? source.OrderByDescending(x => propertyInfo.GetValue(x, null)).Skip(sortingModal.PageSelected * sortingModal.PageSize).Take(sortingModal.PageSize)
: source.OrderBy(x => propertyInfo.GetValue(x, null)).Skip(sortingModal.PageSelected * sortingModal.PageSize).Take(sortingModal.PageSize);
}
}
回答3:
/// Used to indicate the sort order.
/// </summary>
public enum SortOrder
{
/// <summary>
/// Indicates whether the order is ascending.
/// </summary>
Ascending = 0,
/// <summary>
/// Indicates whether the order is descending.
/// </summary>
Descending = 1,
/// <summary>
/// Indicates whether the order is neutral.
/// </summary>
Neutral = 2
}
/// <summary>
/// DTO for sorting and paging
/// </summary>
public class FilterProperties
{
/// <summary>
/// Initializes a new instance of the <see cref="FilterProperties"/> class.
/// </summary>
public FilterProperties()
{
// parameterless constructor
}
/// <summary>
/// Initializes a new instance of the <see cref="FilterProperties"/> class.
/// </summary>
/// <param name="sortColumnName">column name of sorting.</param>
/// <param name="sortOrder">order of the sorting</param>
/// <param name="pageSize">items in the page.</param>
/// <param name="filterValue">value of the filter.</param>
/// <param name="pageselected">current page selected.</param>
public FilterProperties(string sortColumnName, SortOrder sortOrder, int pageSize, string filterValue = "All", int pageselected = 0)
{
this.SortColumnName = sortColumnName;
this.SortOrder = sortOrder;
this.PageSize = pageSize;
this.PageSelected = pageselected;
this.FilterValue = filterValue;
}
/// <summary>
/// Gets or sets the filter column name
/// </summary>
public string FilterColumnName { get; set; }
/// <summary>
/// Gets or sets the filter value
/// </summary>
public string FilterValue { get; set; }
/// <summary>
/// Gets or sets the sort field name.
/// </summary>
public string SortColumnName { get; set; }
/// <summary>
/// Gets or sets the sort direction.
/// </summary>
public SortOrder SortOrder { get; set; }
/// <summary>
/// Gets or sets the page size.
/// </summary>
[Obsolete("Use RecordCount instead (remove this)")]
public int PageSize { get; set; }
/// <summary>
/// Gets or sets the current page index.
/// </summary>
[Obsolete("Use StartRecord instead (remove this)")]
public int PageSelected { get; set; }
/// <summary>
/// Gets or sets the zero-based index of the starting record to return in
/// the filtered result set.
/// </summary>
public int StartRecord { get; set; }
/// <summary>
/// Gets or sets the number of records to return in the filtered result set.
/// </summary>
public int RecordCount { get; set; }
}
}
Extension Method for sorting and paging
public static class SortingAndPagingHelper
{
/// <summary>
/// Returns the list of items of type on which method called
/// </summary>
/// <typeparam name="TSource">This helper can be invoked on IEnumerable type.</typeparam>
/// <param name="source">instance on which this helper is invoked.</param>
/// <param name="sortingModal">Page no</param>
/// <returns>List of items after query being executed on</returns>
public static IEnumerable<TSource> SortingAndPaging<TSource>(
this IEnumerable<TSource> source,
FilterProperties sortingModal)
{
// Is there any sort column supplied?
IEnumerable<TSource> data = source;
if (!string.IsNullOrEmpty(sortingModal.SortColumnName))
{
// Gets the coloumn name that sorting to be done on
PropertyInfo propertyInfo =
data.GetType().GetGenericArguments()[0].GetProperty(sortingModal.SortColumnName);
// Define the sorting function
data = sortingModal.SortOrder == SortOrder.Ascending
? data.OrderBy(x => propertyInfo.GetValue(x, null))
: data.OrderByDescending(x => propertyInfo.GetValue(x, null));
}
// Apply paging to (sorted) data
return sortingModal.RecordCount > 0
? data.Skip(sortingModal.StartRecord).Take(sortingModal.RecordCount)
: data.Skip((sortingModal.PageSelected - 1) * sortingModal.PageSize).Take(sortingModal.PageSize);
}
}
来源：https://stackoverflow.com/questions/15055718/dynamic-filtering-sorting-and-paging-on-generic-list-with-entity-framework