Code contracts static analyzer is complaining about "Warning 2411 CodeContracts: Possibly calling a method on a null reference C:\Users\cathode\Documents\Visual Studio 2012\Projects\nsynth\source\NSynth\FilterInputFrames.cs 47 35 NSynth" on line 21. Presumably it thinks "owner" might be null, which I dont see how it could be.

gistfile1.cs

        /// <summary>
        /// Initializes a new instance of the <see cref="FilterInputFrames"/> class.
        /// </summary>
        /// <param name="owner">The filter that is rendering a frame to which the input frames will be used.</param>
        /// <param name="currentIndex">The frame index being rendered.</param>
        public FilterInputFrames(Filter owner, long currentIndex)
        {
            Contract.Requires(owner != null);
            Contract.Requires(currentIndex >= 0);

            this.locker = new object();
            this.currentIndex = currentIndex;
            this.owner = owner;
            this.frames = new Dictionary<string, Dictionary<long, Frame>>();

            foreach (var slot in owner.Inputs)
            {
                var neededFrames = new Dictionary<long, Frame>();

                // Build a list of indices of frames we need for each input slot.
                foreach (var i in owner.GetInputFramesRequired(slot, currentIndex))
                    neededFrames.Add(i, null);

                this.frames.Add(slot.Name, neededFrames);
            }
        }