Since you really didn't provide an error or anything, I'm just going to show you how I draw them.
I use this extension method for drawing a single line, you will need a white 1x1 texture
public static void DrawLine(this SpriteBatch spriteBatch, Vector2 begin, Vector2 end, Color color, int width = 1)
{
Rectangle r = new Rectangle((int)begin.X, (int)begin.Y, (int)(end - begin).Length()+width, width);
Vector2 v = Vector2.Normalize(begin - end);
float angle = (float)Math.Acos(Vector2.Dot(v, -Vector2.UnitX));
if (begin.Y > end.Y) angle = MathHelper.TwoPi - angle;
spriteBatch.Draw(Pixel, r, null, color, angle, Vector2.Zero, SpriteEffects.None, 0);
}
This will also draw a shape made of points, closed
defines if the shape should be closed or not
public static void DrawPolyLine(this SpriteBatch spriteBatch, Vector2[] points, Color color, int width = 1, bool closed = false)
{
for (int i = 0; i < points.Length - 1; i++)
spriteBatch.DrawLine(points[i], points[i + 1], color, width);
if (closed)
spriteBatch.DrawLine(points[points.Length - 1], points[0], color, width);
}