使用实体框架对通用列表进行动态过滤、排序和分页

Question

我在我的 MVC4 应用程序中使用 jQuery 数据表 (http://www.datatables.net)，您可能知道该表允许服务器端处理。我将在绑定到多个控制器的多个视图中使用该表，因此我想实现一种通用的方式来对数据进行归档、排序和分页，而无需为每个控制器编写一个方法。如果我这样做，它们看起来都一样，但它们将以数据库中的不同实体为目标，并在不同的列上进行文本过滤和排序。这是我今天要做的事情：

    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);
    }

我尝试了几种方法来使这个通用的方法都没有完全起作用——有些是因为我过滤了所有列，有些是因为其他原因。我希望有更好的方法来做到这一点，这样我就可以传递选择列的列或函数并让它工作。

Answer 1

最近刚刚处理了这个问题，我可以告诉你，你想在你的项目中实现动态 linq。 动态 linq 允许您编写查询，例如

results.OrderBy( "id desc" )

和

results.Where( "Name.Contains( 'foo' )" )

希望这些帮助：

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

注意 - 我使用了 jqGrid，但想法保持不变

Answer 2

Dynamic SortingAndPagingHelper扩展方法

/// <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);
    }
}