GCop313.md

GCop 313

"Where should be called first, so it is not doing unnecessary ordering of objects that will be thrown away."

Rule description

Using Where clause after OrderBy clause requires the whole collection to be sorted and then filtered. If we had a million items, only one of which equals to Where condition, we'd be wasting a lot of time ordering results which would be thrown away. So Where should be called first.

Example

var result = foo.OrderBy(o => o.Bar).Where(a => a.Id == id).ToList();

should be 🡻

var result = foo.Where(a => a.Id == id).OrderBy(o => o.Bar).ToList();