2D layerDepth not working XNA 4.0

Question

I'm struggling with getting the depth layer to work properly. No matter what I do, the line is drawn over the top of the circle texture.

public void Draw(SpriteBatch spriteBatch)
    {
        spriteBatch.Begin(
            SpriteSortMode.BackToFront, 
            BlendState.AlphaBlend, 
            null, 
            null, 
            null,
            null, 
            Camera.getTranslation());

        // Draw all planets
        foreach (PlanetNode p in planets)
        {
            p.Draw(spriteBatch);
        }

        spriteBatch.End();
    }

PlanetNode's Draw:

public void Draw(SpriteBatch spriteBatch)
{
    // Draw forwarding line
    if (resourceForward)
    {
        double dist = Math.Sqrt(Math.Pow(location.X - forwardTo.location.X, 2) +
                                Math.Pow(location.Y - forwardTo.location.Y, 2));
        float angle = Utility.GetAngle(location, forwardTo.location);
        spriteBatch.Draw(Textures.BlackPixel, new Rectangle((int)location.X, (int)location.Y, (int)dist, 1), null, Color.Black, angle, Vector2.Zero, SpriteEffects.None, 0.9f);
    }

    // Draw Planet
    if (mouseOver)
    {
        Color c = new Color(color.R + 0.2f, color.G + 0.2f, color.B + 0.2f);
        spriteBatch.Draw(Textures.Planet, position, null, c, 0f, texOrigin, SpriteEffects.None, 0.5f);
    }
    else
        spriteBatch.Draw(Textures.Planet, position, null, color, 0f, texOrigin, SpriteEffects.None, 0.5f);

    // Draw overlay text
    Vector2 size = Textures.TextFont.MeasureString(resources.ToString());
    spriteBatch.DrawString(Textures.TextFont, resources.ToString(), new Vector2(position.X - size.X / 2, position.Y - size.Y / 2), Color.Black);
}

Answer 1

To be honest, judging by the way you're drawing your sprites (which all look fine to me, by the way) it may be better to just switch to SpriteSortMode.Deferred and keep a constant layerDepth.

Doing this and keeping your layerDepths at 0 will produce the result you want.

So, a quick sample:

 spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend);
 //Draw your line here

 //Draw your Planet(s) here with layerDepth set to 0

 spriteBatch.End();

If, for some reason, you desperately need to use layerDepth, I will take another look and update my answer for you.