如何清理if/else LINQ代码

Question

我有这样的东西：

        if (sort == "Customer")
        {
            if (sortDirection == SortDirection.Descending)
                myList = myList.OrderByDescending(e => e.SiteOrganization.Organization.Name).ToList();
            else
                myList = myList.OrderBy(e => e.SiteOrganization.Organization.Name).ToList();
        }
        if (sort == "RequestType")
        {
            if (sortDirection == SortDirection.Descending)
                myList = myList.OrderByDescending(e => e.TypeId).ToList();
            else
                myList = myList.OrderBy(e => e.TypeId).ToList();
        }
        if (sort == "RequestedByShort")
        {
            if (sortDirection == SortDirection.Descending)
                myList = myList.OrderByDescending(e => e.RequestedByUser.ShortName).ToList();
            else
                myList = myList.OrderBy(e => e.RequestedByUser.ShortName).ToList();
        }

我想把这个清理一下，这样就可以了。

if (sortDirection == SortDirection.Descending)
                myList = myList.OrderByDescending(e => e.RequestedByUser.ShortName).ToList();
            else
                myList = myList.OrderBy(e => e.RequestedByUser.ShortName).ToList();

所以我只有一个LINQ查询，不管它是什么“排序”。有什么建议吗？

Answer 1

如果你把你的排序逻辑移到一个方法中，你可以直接把谓词传入，例如

public IList<TSource> SortBy<TSource, TMember>(IEnumerable<TSource> list, Func<TSource, TMember> selector, SortDirection direction)
{
    if (direction == SortDirection.Descending)
        return list.OrderByDescending(selector).ToList();
    else
        return list.OrderBy(selector).ToList();
}
...
if (sort == "Customer") {
    list = SortBy(list, x => x.SiteOrganization.Organization.Name, SortDirection.Descending);
} else if (sort == "RequestType") {
    list = SortBy(list, x => x.TypeId, SortDirection.Ascending);
} else if (sort == "RequestedByShort") {
    list = SortBy(list, x => x.RequestedByUser.ShortName, SortDirection.Descending);
}

Live demo

如果您希望将其用作所有列表的通用解决方案，则可以将其创建为扩展方法

public static class ListExt
{
    public static IList<TSource> SortBy<TSource, TMember>(this IEnumerable<TSource> list, Func<TSource, TMember> selector, SortDirection direction)
    {
        if (direction == SortDirection.Descending) {
            return list.OrderByDescending(selector).ToList();
        } else {
            return list.OrderBy(selector).ToList();
        }
    }
}
...
list = list.SortBy(x => x.TypeId, SortDirection.Ascending);