c# - 动态 Linq 按变量排序

Question

我有一个表，我正在为其编写一些 C# selenium 自动化，需要一些使用 Dynamic Linq 的帮助。假设我有一个基本的 AcctNum、AcctDate 和 AcctName 记录，每个字段都可以由用户排序。他们可以选择 AcctNum (asc)、AcctDate(asc)，最后选择 AcctName (asc)。

那就是:

 var sortedCode = records.OrderBy(r => r.AcctNum)
                         .ThenBy(r => r.AcctDate)
                         .ThenBy(r => r.AcctName)
                         .ToList();

但是用户也可以选择 AcctNum (desc)，AcctDate(asc) 最后是 AcctName (desc)。

我想做的是使用 Dynamic Linq 并使每个排序顺序成为一个变量。

所以像这样:

 //passed in values:
 var varAcctNumOrd = "desc";
 var varDateOrd = "asc";
 var varAcctOrd = "desc";

 var sortedCode = records.OrderBy(r => r.AcctNum, varAcctNumOrd)
                         .ThenBy(r => r.AcctDate, varDateOrd)
                         .ThenBy(r => r.AcctNum, varAcctOrd)
                         .ToList();

这可能吗？

Answer 1

如果我理解正确，下面简单的自定义扩展方法应该可以完成这项工作:

public static class LinqExtensions
{
    public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
        this IEnumerable<TSource> source,
        Func<TSource, TKey> keySelector,
        bool ascending)
    {
        return ascending ? source.OrderBy(keySelector) : source.OrderByDescending(keySelector);
    }

    public static IOrderedEnumerable<TSource> ThenBy<TSource, TKey>(
        this IOrderedEnumerable<TSource> source,
        Func<TSource, TKey> keySelector,
        bool ascending)
    {
        return ascending ? source.ThenBy(keySelector) : source.ThenByDescending(keySelector);
    }

    public static IOrderedQueryable<TSource> OrderBy<TSource, TKey>(
        this IQueryable<TSource> source,
        Expression<Func<TSource, TKey>> keySelector,
        bool ascending)
    {
        return ascending ? source.OrderBy(keySelector) : source.OrderByDescending(keySelector);
    }

    public static IOrderedQueryable<TSource> ThenBy<TSource, TKey>(
        this IOrderedQueryable<TSource> source,
        Expression<Func<TSource, TKey>> keySelector,
        bool ascending)
    {
        return ascending ? source.ThenBy(keySelector) : source.ThenByDescending(keySelector);
    }
}

用法将是:

//passed in values:
var varAcctNumOrd = "desc";
var varDateOrd = "asc";
var varAcctOrd = "desc";

var sortedCode = records.OrderBy(r => r.AcctNum, varAcctNumOrd != "desc")
                        .ThenBy(r => r.AcctDate, varDateOrd != "desc")
                        .ThenBy(r => r.AcctNum, varAcctOrd != "desc")
                        .ToList();