ComputeClosestPoints

请问，我要找到两条线最近的点，用下面的方法会提示：Value cannot be null,Parameter name:reslutList

            var p1 = new XYZ(0, 0, 0);
            var p2 = new XYZ(0, 1, 0);
            var p3 = new XYZ(1, 2, 0);
            var p4 = new XYZ(1, 3, 0);
            var line1 = Line.CreateBound(p1, p2);
            var line2 = Line.CreateBound(p3, p4);

            IList<ClosestPointsPairBetweenTwoCurves> resultList=null;
            line1.ComputeClosestPoints(line2,true,false,true,out resultList);//错误提示在这一行：Value cannot be null,Parameter name:reslutList
            var points=  resultList?.FirstOrDefault();
            var point = points.XYZPointOnSecondCurve;
            


            TaskDialog.Show("revit", point.ToString());

line1.ComputeClosestPoints(line2,true,false,true,out resultList);
这个函数的实现的代码在哪里呢