动态Linq变量排序 [英] Dynamic Linq Order By Variable

问题描述

我有一张表，我正在为此编写一些 C# selenium 自动化程序，并且在使用Dynamic Linq时需要一些帮助.假设我有一个基本的 AcctNum ， AcctDate 和 AcctName 记录，并且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).

I have a table that I am writing some C# selenium automation for and need some help using Dynamic Linq. Let's say I have a basic AcctNum, AcctDate and AcctName record and each field can be sorted by the user. They could choose AcctNum (asc), AcctDate(asc) and finally AcctName (asc).

那将是:

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

不过，用户还可以选择 AcctNum (描述)， AcctDate (描述)，最后选择 AcctName (描述).

However the user could also choose AcctNum (desc), AcctDate(asc) and finally 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.

What I would like to do is use Dynamic Linq and make each sort order a variable.

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?

推荐答案

如果我理解正确，那么以下简单的自定义扩展方法就可以完成这项工作:

If I understand correctly, the following simple custom extension methods should do the job:

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);
    }
}

其用法将是:

//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();

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