creating a flashlight in XNA

Can you be more specific about your game? For a start, is this 2D or 3D?

This is not for a game persay, just tweaking the code found in the book. I was trying to change it so that the light used in the example is more focues like a flashlight beam. I don't have access to the code used in the chapter at the moment, but can post it as soon as practicle.

The code is 3D as the author has created a camera system and is demonstarting the use of lighting by having a light follow the movement of the camera.

So a spotlight ?

Ya, I guess spotlight would be the best way to describe it.

Something similiar to the flashlight effect in say Slenderman or any other of the horror-survial-at-night genre of games.

Basically it's just a spot-light, you can do more fancy texture projections or more complex lighting equations to give interesting variations..

Compute the dot product of the light-pixel vector and the light-target vector. Then you can use that to produce a light-cone.