How to return a "chain" of OrderBy() calls for reusability

I have some LINQ-to-objects code as follows, which gets the items in a collection in a specific "complex" order:

var items = this.Items.OrderBy(a => a.DisplayType == DisplayType.Integer ? 0 : 1)
                      .ThenBy(a => a.DisplayType == isplayType.String ? 0 : 1)
                      .ThenBy(a => a.Name);

This works really well. However, I want to be able to reuse this "chain" without duplicating 开发者_运维百科the code.

I can do this fine while all of the types of the properties we're sorting on are the same:

private static Func<Column, int> GetOrderBy()
{
    return a => a.DisplayType == FieldDisplayType.Integer ? 0 :
        a.DisplayType == FieldDisplayType.String ? 1 : 2;
}

var items = this.Items.OrderBy(GetOrderBy());

but then I don't see how I can include a.Name - because the return type is Func, and Column.Name is a string.

Any help appreciated.

Tom

If you want to reuse that ordering, I would write an extension method which applies the ordering, instead of calling OrderBy:

internal static IOrderedEnumerable<Column> OrderByDefaults
    (this IEnumerable<Column> source)
{
    return source.OrderBy(a => a.DisplayType != FieldDisplayType.Integer)
                 .ThenBy(a => a.DisplayType != FieldDisplayType.String);
}

then call it with:

var items = this.Items.OrderByDefaults()
                      .ThenBy(a => a.Name);

Two points:

• I've not bothered with integers: "false" sorts less than "true", so I believe this does what you want. You can put it back to using integers for each property though
• The disadvantage of this approach is that you need to a static nongeneric top-level type for the extension method.

I would definitely stick to OrderBy/ThenBy/ThenBy instead of building your own big comparer with the conditional clause - simply because it's a lot easier to read, IMO.