我并不认为这种情况很难找到,但看起来似乎是这样。这就是情况。
我有一个 ApplySort 方法,该方法接收来自mvc页面的3个参数。
private List<dynamic> ApplySort(List<dynamic> listToBeSorted, string sortBy, string sortOrder)
{
if (String.IsNullOrEmpty(sortBy))
sortBy = "createddate";
if (String.IsNullOrEmpty(sortOrder) || sortOrder.Trim() != "0")
sortOrder = "1"; // 1 = descending, 0 = ascending
if (sortOrder == "1")
{
switch (sortBy)
{
case "name":
listToBeSorted = listToBeSorted.OrderByDescending(a => a.name).ToList();
break;
case "assigned":
listToBeSorted = listToBeSorted.OrderByDescending(a => a.title).ToList();
break;
case "duedate":
listToBeSorted = listToBeSorted.OrderByDescending(a => a.end).ToList();
break;
case "status":
listToBeSorted = listToBeSorted.OrderByDescending(a => a.title).ToList();
break;
default:
listToBeSorted = listToBeSorted.OrderByDescending(a => a.title).ToList();
break;
}
}
else
{
// same code as in if-block, with just OrderBy calls instead of OrderByDescending
}
return listToBeSorted;
}
两个问题:
1)方法似乎不必要地长(if和else块内部的代码非常相似)。
2)我希望能够使用多列进行排序。 sortBy param可以包含&#34; name,title,createddate,status&#34;等值。因此,应用的排序应首先按名称,然后按标题,然后按创建日期...依此类推。 我可以通过顺序检查params来使用 ThenBy 。 但是如何基于param值动态应用ThenBy 链,其中ThenBy的数量可以变化。
string[] sortParams = sortBy.Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries);
listToBeSorted.OrderBy(i=>i.sortParams[0]).ThenBy(j=>j.sortParams[1]).ThenBy(k=>k.sortParams[2])...(so on till sortParams.length)
我该怎么做?另外,我如何使用sortOrder参数在同一行中升序或降序排序,而不是使用if-else。
答案 0 :(得分:0)
您可以使用Func<string, IComparable>
映射到您班级的属性来创建字典。
public class ItemWithProperty
{
public string Property { get; set; }
}
public static void Main()
{
Dictionary<string, Func<ItemWithProperty, IComparable>> stringPropertyMap = new Dictionary<string, Func<ItemWithProperty, IComparable>>()
{
{"param1", item => item.Property}
};
List<ItemWithProperty> toBeOrdered = new List<ItemWithProperty>();
string[] parameters = {"param1"};
var sorted = toBeOrdered.OrderBy(stringPropertyMap[parameters[0]]);
}
答案 1 :(得分:-1)
如果更改方法签名,则使用此方法:
private static IEnumerable<dynamic> ApplySort(IEnumerable<dynamic> listToBeSorted, ICollection<KeyValuePair<string, string>> sorters)
{
var orderBy = (sorters == null || sorters.Count == 0) ? new KeyValuePair<string, string>("createddate", "1") : sorters.First();
var thenBys = (sorters == null || sorters.Count == 1) ? new List<KeyValuePair<string, string>>() : sorters.Except(Enumerable.Repeat(orderBy, 1));
var orderedEnumerable = orderBy.Value == "1"
? listToBeSorted.OrderBy(x => GetPropertyValue(x, orderBy.Key))
: listToBeSorted.OrderByDescending(x => GetPropertyValue(x, orderBy.Key));
orderedEnumerable = thenBys.Aggregate(orderedEnumerable, (current, thenBy) => thenBy.Value == "1"
? current.ThenBy(x => GetPropertyValue(x, thenBy.Key))
: current.ThenByDescending(x => GetPropertyValue(x, thenBy.Key)));
return orderedEnumerable.ToList();
}
private static object GetPropertyValue(dynamic obj, string propName)
{
Type t = obj.GetType();
return t.GetProperty(propName).GetValue(obj, null);
}
尝试:
static void Main(string[] args)
{
var list = new List<dynamic>();
list.Add(new { name = "Billy" });
list.Add(new { name = "Johnny" });
list.Add(new { name = "Ali" });
var list2 = ApplySort(list, new List<KeyValuePair<string, string>>(new List<KeyValuePair<string, string>> { new KeyValuePair<string, string>("name", "1") }));
foreach (var o in list2)
{
Console.WriteLine(o.name);
}
Console.ReadLine();
}