Is there any way to find out if a point with a certain lat and long is located on any road...

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C#

hello,

I am writing a program in c# which should finds the nearest path(road) between to points in the city. I needed to access the road data,like the coordinates of beginning and end of the roads, maybe a complete data base. I did not know how i can access to such an information or file. so for simplicity i assumed some certain vertices and the edges(the connection between the vertixes). now i have a point(a coordinate of a specific location). I want to see on which edge this point is located. I see by just having information abt start n end of vertices and the connection between them (edges=roads) I can not locate a position of a point on the roads. I need to know if there is any way to find out if a point with a specific coordinates is located on a specific road.

the thing is my knowledge abt these things is very limited.
I really appreciate any help or suggestion.

many thanks,