C# List.Find() seems not working when list is huge

Question

I have a huge List, say 10 million items in it, which I'm trying to find a specific value in the list.

Here's my item

struct reference
{
    public double GPST;
    public byte cls;
    public ushort fn;
    public int ret_num;
}

and here's my query code

 List<reference> ref_pts;

 List<reference> result = ref_pts.FindAll(delegate(reference obj) { return obj.GPST == pt.GPST; });

where pt.GPST is the value I want to find in List

Is it just because the size is too big, which Find method not working(always return nothing)?

Answer 1

You cant compare doubles for equality like this, use an epsilon to compare against:

bool CompareDoubles2 (double A, double B) 
{
   diff = A - B;
   return (diff < EPSILON) && (-diff < EPSILON);
}

EPSILON is a very small number, for details see here and here