threshhold line in the horizontal line

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C#

ZedGraph

This may be simple, but I'm unable to figure it out. I have a linear graph in zed graph. Now I want to add a straight horizontal line for a threshold Y value in, say, Red so that it shows in the graph along with the actual data. I already know the threshold value for each of my counters.

double threshHoldY = 2;
LineObj threshHoldLine = new LineObj(
    Color.Red,
    graphPane.XAxis.Scale.Min,
    threshHoldY,
    graphPane.XAxis.Scale.Max,
    threshHoldY);
graphPane.GraphObjList.Add(threshHoldLine);

this is the code i am trying but only draws the line in the beginning of the x- axis, where as i want it for the entire x-axixs.