source: OniSplit/Dae/EffectParameter.cs@ 1118

using System;

namespace Oni.Dae
{
        internal class EffectParameter
        {
                private object value;
                private string reference;

                public EffectParameter()
                {
                }

                public EffectParameter(string sid, object value)
                {
                        Sid = sid;
                        this.value = value;
                        SetValueOwner(this);
                }

                public EffectParameter(string sid, object value, Effect parent)
                {
                        Sid = sid;
                        this.value = value;
                }

                public string Sid { get; set; }
                public string Semantic { get; set; }

                public object Value
                {
                        get
                        {
                                return value;
                        }
                        set
                        {
                                SetValueOwner(null);

                                this.value = value;

                                if (value != null)
                                        reference = null;

                                SetValueOwner(this);
                        }
                }

                private void SetValueOwner(EffectParameter owner)
                {
                        EffectSampler sampler = value as EffectSampler;

                        if (sampler != null)
                        {
                                sampler.Owner = owner;
                                return;
                        }

                        EffectSurface surface = value as EffectSurface;

                        if (surface != null)
                        {
                                surface.DeclaringParameter = owner;
                                return;
                        }
                }

                public string Reference
                {
                        get
                        {
                                return reference;
                        }
                        set
                        {
                                reference = value;

                                if (reference != null)
                                        this.value = null;
                        }
                }
        }
}