Linq 如何优化排序代码？

我想优化以下代码行进行排序

public ViewResult Index(string sortorder, int? pagesize, int? page)
        {
            int pageSize = pagesize ?? 10;
            if (Request.HttpMethod != "GET")
            {
                page = 1;
                pageSize = 10;
            }
            ViewBag.SelectedPageSize = pageSize;

            ViewBag.CurrentSort = sortorder;
            ViewBag.FirstNameSortParm = String.IsNullOrEmpty(sortorder) ? "FirstName desc" : "";
            ViewBag.LastNameSortParm = sortorder == "LastName" ? "LastName desc" : "LastName";
            ViewBag.DepNameSortParm = sortorder == "depName" ? "depName desc" : "depName";

            var joined = from tm in db.TabMasters select tm;
            switch (sortorder)
            {
                case "FirstName":
                    joined = joined.OrderBy(m => m.FirstName);
                    break;
                case "FirstName desc":
                    joined = joined.OrderByDescending(m => m.FirstName);
                    break;
                case "LastName":
                    joined = joined.OrderBy(m => m.LastName);
                    break;
                case "LastName desc":
                    joined = joined.OrderByDescending(m => m.LastName);
                    break;
                case "depName":
                    joined = joined.OrderBy(m => m.depName);
                    break;
                case "depName desc":
                    joined = joined.OrderByDescending(m => m.depName);
                    break;
                default:
                    joined = joined.OrderBy(m => m.FirstName);
                    break;
            }

            int pageIndex = (page ?? 1) - 1;
            int start = (pageIndex * pageSize);
            ViewBag.TotalRecord = joined.Count();
            ViewBag.StartRecord = start + 1;
            ViewBag.EndRecord = ((start + pageSize) >= ViewBag.TotalRecord) ? ViewBag.TotalRecord : (start + pageSize);
            return View(joined.ToPagedList(pageIndex, pageSize));
        }

因为如果我有更多的10个字段要执行排序，这是一种非常乏味的方式

谢谢，

---

Imdadhusen

我对您的实际目标有点模糊，但对于切换部分，您可以使用如下扩展方法

public static class SortExtensions
{
    public static IEnumerable<T> SortByField<T>(this IEnumerable<T> sequence, string sortOrder)
    {
        var tokens = sortOrder.Trim().Split(' ');
        var field = tokens[0];
        var direction = tokens.Skip(1).Single().ToLower();
        var prop = typeof(T).GetProperty(field);
        return direction == "desc"
                   ? sequence.OrderByDescending(m => prop.GetValue(m, null))
                   : sequence.OrderBy(m => prop.GetValue(m, null));
    }
}

根据评论进行编辑：

在没有任何错误处理的情况下，行typeof（T）.GetProperty（field）是脆弱的。它依赖于第一个令牌作为T类型的公共属性的名称。如果名称与属性不匹配，它将返回null。包括是否匹配字段名。有一个类似的函数用于获取FieldInfo

---

GetField（field）将返回具有给定名称的公共字段的fieldinfo对象，否则为null。要获取字段的值，只需省略GetValue调用的最后一个参数。

您应该看看Linq.DynamicQuery。 这篇博文中有更多信息

该库允许您编写以下代码：

var query = northwind.Products
                     .Where("CategoryID = 3 AND UnitPrice > 3")
                     .OrderBy("SupplierID");

而不是

var query = from p in northwind.Products
                where p.CategoryID == 3 && p.UnitPrice > 3
                orderby p.SupplierID
                select p;

如果要添加排序方向：

var query = northwind.Products.OrderBy("SupplierID Descending");

---

回答得好，我应该为SortByField方法创建一个类吗？你能帮我写完整的类文件吗？见更新。没有完整的类和如何使用SortByField的示例，但这给出了（5）个生成错误：找不到类型或命名空间名称“T”（是否缺少using指令或程序集引用？@imdadhusen很抱歉，我的手机上没有IDE。它现在可以编译了。（错过了signarture方法的类型参数，我使用的Linq方法拼写错误）感谢您宝贵的回复，我感谢您的努力。但我仍然得到错误：var prop=typeof（T）.GetProperty（field）；这将始终返回NULL

var query = northwind.Products.OrderBy("SupplierID Descending");