You can use Enumerable.Any
In your code:
See also 'Testing for equality' on http://msdn.microsoft.com/en-us/library/system.double.aspx
In your code:
series.Points.Any(p => p.X.Equals(X) && p.Y.Equals(Y))See also 'Testing for equality' on http://msdn.microsoft.com/en-us/library/system.double.aspx
