Dazed Dazed - 2 months ago 24
C# Question

Dynamic Linq Order By Variable

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).

That would be:

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


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

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

So something like:

//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();


Is this possible?

Answer

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);
    }
}

And the usage will be:

//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();