Question

I’m using LINQ to order some data, but I have zero or more OrderBy clauses to apply.

As I don’t know how many order clauses I have, I cannot do:

var myItems = dataContext.MyItems
    .OrderBy(i => i.ColumnA)
    .ThenBy(i => i.ColumnB)
    .ThenBy(i => i.ColumnC)
    .ThenBy(i => i.ColumnD)
    // etc.

Logically, I need something like:

var myItems = dataContext.MyItems;
foreach (var orderClause in myOrderClauses)
{
    myItems = myItems.SubOrderMagicallyBy(orderClause);
}

Obviously this is hopeless, so any ideas would be greatly appreciated.

Answer 1

Why doesn’t it work with the foreach?
You just need to handle the special case of the first order clause:

IQueryable<MyItem> myItems = dataContext.MyItems;
bool first=true;
foreach (var orderClause in myOrderClauses)
{
    if(first)
    {
        myItems = myItems.OrderBy(orderClause);
        first = false;
    }
    else
        myItems = myItems.ThenBy(orderClause);
}

This assumes, that myOrderClauses is of type IEnumerable<Expression<Func<TSource, TKey>>>.