Rim Lighting

hi im mo and i like this RimShader and when i tried to use it on my Game Environment it give me this Error “Object reference not set to an instance of an object.” and im using XNA 2.0 thnx for help.

Matrix[] bones;
bones = new Matrix[level.Bones.Count];
level.CopyBoneTransformsTo(bones);

foreach (ModelMesh mesh in level.Meshes)
{
foreach (Effect effects in mesh.Effects)
{ effects.Parameters["World"].SetValue(bones[mesh.ParentBone.Index]);
effects.Parameters["View"].SetValue(view);
effects.Parameters["ViewI"].SetValue(Matrix.Invert(view));
effects.Parameters["Projection"].SetValue(Projection);

//customize the effect
effects.Parameters["Rim_Start"].SetValue(0.4f);
effects.Parameters["Rim_End"].SetValue(1.0f);
effects.Parameters["Rim_Multiplier"].SetValue(0.9f);
effects.Parameters["Rim_Color"].SetValue(Color.White.ToVector4());

//Other Variants
////////////////////////////////////////////////////////////////////////////
// Rim_Start || Rim_End || Rim_Multiplier || Rim_Color ||
////////////////////////////////////////////////////////////////////////////
// 0.5f || 0.1f || 0.5f || PeachPuff ||
// 0.4f || 1.0f || 1.6f || Red ||
// 0.4f || 0.5f || -1.4f || White ||
// 0.0f || 1.0f || 0.5f || Chocolate ||
// 0.1f || 0.3f || 0.8f || SlateBlue ||
///////////////////////////////////////////////////////////////////////////
}
mesh.Draw();
}

“effects.Parameters[”ViewI”].SetValue(Matrix.Invert(view));” this is line of error

you right i Found that But when i use the Model Without Texture just use colors, It gives me Gray Color so any Info. and thnx for help
Regards

thnx 4 help but all what i need is to know how to make a simple light with shader support untextured models and also textured so if u know learning resource that will be great …