SpriteBatch does not use custom Effect

[gitfool]

Following up from Paradox Answers.
Hack the Custom Effect Sample to use a SpriteBatch instead of a PrimitiveQuad:

private void RenderQuad(RenderContext renderContext)
{
    //GraphicsDevice.SetBlendState(GraphicsDevice.BlendStates.NonPremultiplied);
    customEffect.Parameters.Set(CustomEffectKeys.Phase, -3 * (float)this.UpdateTime.Total.TotalSeconds);
    //quad.Draw(paradoxTexture, samplingState, Color.White);
    var destination = new RectangleF(0, 0, GraphicsDevice.BackBuffer.Width, GraphicsDevice.BackBuffer.Height);
    spriteBatch.Begin(SpriteSortMode.Immediate, GraphicsDevice.BlendStates.NonPremultiplied, samplingState, effect: customEffect);
    spriteBatch.Draw(paradoxTexture, destination, Color.White);
    spriteBatch.End();
}

The custom effect is never applied. Stepping the code in the debugger, after spriteBatch.Begin the spriteBatch.Effect property is of type BatchDefaultEffect, not CustomEffect.

[gitfool]

Digging further, BaseBatch<SpriteBatch.SpriteDrawInfo>.Begin is resetting the Effect property:

if (!resourceContextPerEffect.ContainsKey(Effect))
{
    Effect = DefaultEffect;
}

That's why I wasn't sure if it was a bug or misuse on my behalf, where I had to somehow set up this resourceContextPerEffect with my custom effect, but there was nothing obvious that I could see with Reflector.

[xoofx]

This should be fixed for alpha10

[gitfool]

For the record, I updated Xamarin tools today (beta channel), so I'm now using Xamarin 3.8.13.0, Xamarin.Android 4.18.0.34 and Xamarin iOS 8.2.0.0.

This works fine on Windows, but fails on Android and iOS, rendering a blank screen.