When can EffectParameter.SetValue() be called?

1

Hello:

Im triying to create an ilumination system for a 2D game. For that, I draw each light into a separated buffer. In order to make the maximum amount of light in the buffer exceed when necessary (1,1,1), I draw each light with a shader in a RenderTarget configured with HalfVector4 surface mode:

float3 Bright=float3(1.0,1.0,1.0); /*<-Setted parameter*/
[...]
float4 MainPS(VertexShaderOutput input) : COLOR
{
	float4 baseColor = tex2D(SpriteTextureSampler,input.TextureCoordinates) * input.Color;
	return float4(baseColor.x*Bright.x, baseColor.y*Bright.y, baseColor.z*Bright.z, baseColor.w);
}

At first it worked fine, just as I expected but after some not sustantial changes, it stopped doing so.

I suspect it is because the Bright EffectParamter is being updated whitout starting a new SpriteBatch.Begin cycle. Currently, my code only changes the draw params when necessary in this way:

SpriteBatchDrawParams lightParams = new(){blendState=BlendState.Additive, effect=LightsShader};
            SpriteBatchDrawParams? drawParams = null;
            for(int i = 0; i<ToDrawInBufferElsCount; i++)
            {
                GameObject obj = ToDrawInBuffer[i];
                SpriteBatchDrawParams newParams = obj is LightObject?lightParams:GetObjectDrawParams(obj as IDrawnObject);
                if (drawParams != newParams /*|| true*/)/*Note that when the '|| true' is uncommented, it always works at the expense of more draw calls.*/
                {
                    if (drawParams != null) spriteBatch.End();
                    drawParams = newParams;
                    newParams.StartSpriteBatch(spriteBatch);
                }
                if (obj is LightObject light)
                {
                    LightsShader.Parameters["Bright"].SetValue(light.LightColor);
                    Console.WriteLine(drawParams?.effect);
                    light.DrawLights(spriteBatch);
                } else if (obj is IDrawnObject drawnObject)
                {
                    drawnObject.Draw(DrawItDataByObj[obj]);
                }
            }

So if it has to draw multiple lights back to back, it doesn’t change of drawing begin/end, but if there is any non-light object in between the light calls, it changes to the proper parameters (that make the obj being drawn in black with a custom BlendState, since is the Lights Buffer, not the main render.)

The thing is that even if I uncomment the || true, the EffectParameter.SetValue is still being called after the SpriteBatch.Begin.

So:

When should EffectParameter.SetValue be called?