GroupingProjection fails if groupkey does not implement IComparable

[sfmskywalker]

The following code will fail with a System.ArgumentException: At least one object must implement IComparable. if:

1. TGroupKey is not comparable
2. No Group comparer is specified.

var projection =
                    mSourceCollection.ToArray()
                        .Where(mFilterPredicate)
                        .OrderBy(mOrderKeySelector, mOrderKeyComparer)
                        .GroupBy(mGroupKeySelector)
                        .Select(group => new Group(group.Key, group))
                        .OrderBy(x => x.Key, mGroupKeyComparer)
                        .ToArray();

Specifically, this line:

.OrderBy(x => x.Key, mGroupKeyComparer)

Either the key must implement IComparable, or a group key comparer must be specified.
If no group key comparer is specified, then the OrderBy should simply not happen. The following code fixes this issue:

var projectionQuery =
                    mSourceCollection.ToArray()
                        .Where(mFilterPredicate)
                        .OrderBy(mOrderKeySelector, mOrderKeyComparer)
                        .GroupBy(mGroupKeySelector)
                        .Select(group => new Group(group.Key, group));

                if (mGroupKeyComparer != null)
                    projectionQuery = projectionQuery.OrderBy(x => x.Key, mGroupKeyComparer);

                var projection = projectionQuery.ToArray();