I have a point on line let say x,y and a list of points i want to find out the points closest to the point x,y at both ends for example

------------------------------ x1,y1

p1------------------------------|----------------------------------p2

and a list of point(p2,p3,p4,p5.......) now i want to find the closest two points

------------------------- p5-----x1,y1----p6

p1-----------------------|-------|---------|----------------------------------p2

is there any functioality available in arcobject that can perform this operation?

------------------------------ x1,y1

p1------------------------------|----------------------------------p2

and a list of point(p2,p3,p4,p5.......) now i want to find the closest two points

------------------------- p5-----x1,y1----p6

p1-----------------------|-------|---------|----------------------------------p2

is there any functioality available in arcobject that can perform this operation?

Use linear referencing. Locate Features Along Route to create an event table of the points on the line. Then you can find the measure of the point and select Min and Max of the points in the measure ranges above and below that measure or read the points in ascending and descending sorted order on the RouteID and measures.