Draw Vector3 between two objects

How is it possible to draw a directional vector between two spheres? I cant find a method to draw a line in 3D. I would really appreciate your help.

e.g Object1.position = (1, 1, 1) and Object2.position = (4, 2, 5) How can i draw the Vector3 from the position of Object1 to position of Object2?

Edit: in C#

Have a look at this tutorial.