No matching point found between 2 collections of System.Windows.Points

I have a function where I try to find a matching Point between 2 collections of 4 Points each, but sometimes the function reports the collections do not share a common Point even though in the debugger I see they do. is the debugger not showing me the full precision of the points so I do not see the difference? or is there something else going on here? here's the code to blame:

public static Point CorrectForAllowedDrawArea(Point previousDisplayLocation, Point newDisplayLocation, Rect displayLimitedArea, Rect newBoundingBox)
{
    // get area that encloses both rectangles
    Rect enclosingRect = Rect.Union(displayLimitedArea, newBoundingBox);
    // get corners of outer rectangle, index matters for getting opposite corner
    var outsideCorners = new[] { enclosingRect.TopLeft, enclosingRect.TopRight, enclosingRect.BottomRight, enclosingRect.BottomLeft }.ToList();
    // get corners of inner rectangle
    var insideCorners = new[] { displayLimitedArea.TopLeft, displayLimitedArea.TopRight, displayLimitedArea.BottomRight, displayLimitedArea.BottomLeft }.ToList();
    // get the first found corner that both rectangles share
    Point sharedCorner = outsideCorners.FirstOrDefault((corner) => insideCorners.Contains(corner));
    // find the index of the opposite corner
    int oppositeCornerIndex = (outsideCorners.IndexOf(sharedCorner) + 2) % 4;

on the last line 's开发者_如何转开发haredCorner' is sometimes set to default(Point) even though both Point collections appear to share 1 Point.

EDIT: I should mention if I place the debugger back to the top of the function and restart it still does not find the matching point. I should also mention that this function uses the Point class of the System.Windows namespace and not of the System.Drawing namespace! Thanks for pointing this out to me in the comments.

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We really need to see what the definition of insideCorners.Contains(corner) is, but I suspect that your problem is due to the inherent inaccuracies with floating point numbers.

You cannot compare two floating point values like this:

if (a == b)
{
    // Values are equal
}

especially if either a or b are calculated values.

You'll need to implement something along the lines of:

if (Math.Abs(a - b) < some_small_value)
{
    // Values are equal
}