diff --git a/ICD.Common.Utils/Collections/BiDictionary.cs b/ICD.Common.Utils/Collections/BiDictionary.cs
index 3467d01..60e3823 100644
--- a/ICD.Common.Utils/Collections/BiDictionary.cs
+++ b/ICD.Common.Utils/Collections/BiDictionary.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using ICD.Common.Properties;
 
 namespace ICD.Common.Utils.Collections
 {
@@ -20,8 +21,10 @@ namespace ICD.Common.Utils.Collections
 
 		public bool IsReadOnly { get { return false; } }
 
+		[NotNull]
 		public ICollection<TKey> Keys { get { return m_KeyToValue.Keys; } }
 
+		[NotNull]
 		public ICollection<TValue> Values { get { return m_ValueToKey.Keys; } }
 
 		#endregion
@@ -30,21 +33,20 @@ namespace ICD.Common.Utils.Collections
 		/// Constructor.
 		/// </summary>
 		public BiDictionary()
-			: this(null)
 		{
+			m_KeyToValue = new Dictionary<TKey, TValue>();
+			m_ValueToKey = new Dictionary<TValue, TKey>();
 		}
 
 		/// <summary>
 		/// Constructor.
 		/// </summary>
 		/// <param name="dict"></param>
-		public BiDictionary(Dictionary<TKey, TValue> dict)
+		public BiDictionary([NotNull] Dictionary<TKey, TValue> dict)
+			: this()
 		{
-			m_KeyToValue = new Dictionary<TKey, TValue>();
-			m_ValueToKey = new Dictionary<TValue, TKey>();
-
 			if (dict == null)
-				return;
+				throw new ArgumentNullException("dict");
 
 			foreach (KeyValuePair<TKey, TValue> kvp in dict)
 				Add(kvp.Key, kvp.Value);
@@ -58,24 +60,31 @@ namespace ICD.Common.Utils.Collections
 			m_ValueToKey.Clear();
 		}
 
-		public bool ContainsKey(TKey key)
+		public bool ContainsKey([NotNull] TKey key)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			return m_KeyToValue.ContainsKey(key);
 		}
 
-		public bool ContainsValue(TValue value)
+		public bool ContainsValue([NotNull] TValue value)
 		{
 			return m_ValueToKey.ContainsKey(value);
 		}
 
-		public void Add(TKey key, TValue value)
+		public void Add([NotNull] TKey key, [NotNull] TValue value)
 		{
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("key");
 
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (value == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("value");
 
 			if (ContainsKey(key))
@@ -88,14 +97,16 @@ namespace ICD.Common.Utils.Collections
 			m_ValueToKey.Add(value, key);
 		}
 
-		public void Set(TKey key, TValue value)
+		public void Set([NotNull] TKey key, [NotNull] TValue value)
 		{
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("key");
 
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (value == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("value");
 
 			RemoveKey(key);
@@ -104,18 +115,35 @@ namespace ICD.Common.Utils.Collections
 			Add(key, value);
 		}
 
-		public TKey GetKey(TValue value)
+		[NotNull]
+		public TKey GetKey([NotNull] TValue value)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (value == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("value");
+
 			return m_ValueToKey[value];
 		}
 
-		public TValue GetValue(TKey key)
+		[NotNull]
+		public TValue GetValue([NotNull] TKey key)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			return m_KeyToValue[key];
 		}
 
-		public bool RemoveKey(TKey key)
+		public bool RemoveKey([NotNull] TKey key)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			if (!ContainsKey(key))
 				return false;
 
@@ -127,8 +155,13 @@ namespace ICD.Common.Utils.Collections
 			return true;
 		}
 
-		public bool RemoveValue(TValue value)
+		public bool RemoveValue([NotNull] TValue value)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (value == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("value");
+
 			if (!ContainsValue(value))
 				return false;
 
@@ -137,13 +170,23 @@ namespace ICD.Common.Utils.Collections
 			return RemoveKey(key);
 		}
 
-		public bool TryGetValue(TKey key, out TValue value)
+		public bool TryGetValue([NotNull] TKey key, out TValue value)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			return m_KeyToValue.TryGetValue(key, out value);
 		}
 
-		public bool TryGetKey(TValue value, out TKey key)
+		public bool TryGetKey([NotNull] TValue value, out TKey key)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (value == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("value");
+
 			return m_ValueToKey.TryGetValue(value, out key);
 		}
 
@@ -151,9 +194,10 @@ namespace ICD.Common.Utils.Collections
 
 		#region IDictionary
 
-		TValue IDictionary<TKey, TValue>.this[TKey key] { get { return GetValue(key); } set { Set(key, value); } }
+		[NotNull]
+		TValue IDictionary<TKey, TValue>.this[[NotNull] TKey key] { get { return GetValue(key); } set { Set(key, value); } }
 
-		bool IDictionary<TKey, TValue>.Remove(TKey key)
+		bool IDictionary<TKey, TValue>.Remove([NotNull] TKey key)
 		{
 			return RemoveKey(key);
 		}
@@ -177,7 +221,7 @@ namespace ICD.Common.Utils.Collections
 			return RemoveKey(item.Key);
 		}
 
-		void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
+		void ICollection<KeyValuePair<TKey, TValue>>.CopyTo([NotNull] KeyValuePair<TKey, TValue>[] array, int arrayIndex)
 		{
 			(m_KeyToValue as IDictionary<TKey, TValue>).CopyTo(array, arrayIndex);
 		}
@@ -186,11 +230,13 @@ namespace ICD.Common.Utils.Collections
 
 		#region IEnumerable
 
+		[NotNull]
 		public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
 		{
 			return m_KeyToValue.GetEnumerator();
 		}
 
+		[NotNull]
 		IEnumerator IEnumerable.GetEnumerator()
 		{
 			return GetEnumerator();
diff --git a/ICD.Common.Utils/Collections/IcdHashSet.cs b/ICD.Common.Utils/Collections/IcdHashSet.cs
index 8f46f92..af85962 100644
--- a/ICD.Common.Utils/Collections/IcdHashSet.cs
+++ b/ICD.Common.Utils/Collections/IcdHashSet.cs
@@ -49,7 +49,7 @@ namespace ICD.Common.Utils.Collections
 		/// Constructor.
 		/// </summary>
 		/// <param name="items"></param>
-		public IcdHashSet(IEnumerable<T> items)
+		public IcdHashSet([NotNull] IEnumerable<T> items)
 			: this(EqualityComparer<T>.Default, items)
 		{
 		}
@@ -58,7 +58,7 @@ namespace ICD.Common.Utils.Collections
 		/// Constructor.
 		/// </summary>
 		/// <param name="comparer"></param>
-		public IcdHashSet(IEqualityComparer<T> comparer)
+		public IcdHashSet([NotNull] IEqualityComparer<T> comparer)
 			: this(comparer, Enumerable.Empty<T>())
 		{
 		}
@@ -68,7 +68,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="comparer"></param>
 		/// <param name="items"></param>
-		public IcdHashSet(IEqualityComparer<T> comparer, IEnumerable<T> items)
+		public IcdHashSet([NotNull] IEqualityComparer<T> comparer, [NotNull] IEnumerable<T> items)
 		{
 			if (comparer == null)
 				throw new ArgumentNullException("comparer");
@@ -91,7 +91,8 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public IcdHashSet<T> Union(IEnumerable<T> set)
+		[NotNull]
+		public IcdHashSet<T> Union([NotNull] IEnumerable<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -108,7 +109,8 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public IcdHashSet<T> Subtract(IEnumerable<T> set)
+		[NotNull]
+		public IcdHashSet<T> Subtract([NotNull] IEnumerable<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -127,7 +129,8 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public IcdHashSet<T> Intersection(IEnumerable<T> set)
+		[NotNull]
+		public IcdHashSet<T> Intersection([NotNull] IEnumerable<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -146,7 +149,8 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public IcdHashSet<T> NonIntersection(IEnumerable<T> set)
+		[NotNull]
+		public IcdHashSet<T> NonIntersection([NotNull] IEnumerable<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -170,7 +174,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public bool IsSubsetOf(IcdHashSet<T> set)
+		public bool IsSubsetOf([NotNull] IcdHashSet<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -184,7 +188,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public bool IsProperSubsetOf(IcdHashSet<T> set)
+		public bool IsProperSubsetOf([NotNull] IcdHashSet<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -198,7 +202,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public bool IsSupersetOf(IcdHashSet<T> set)
+		public bool IsSupersetOf([NotNull] IcdHashSet<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -212,7 +216,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public bool IsProperSupersetOf(IcdHashSet<T> set)
+		public bool IsProperSupersetOf([NotNull] IcdHashSet<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -226,7 +230,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="set"></param>
 		/// <returns></returns>
 		[PublicAPI]
-		public bool SetEquals(IcdHashSet<T> set)
+		public bool SetEquals([NotNull] IcdHashSet<T> set)
 		{
 			if (set == null)
 				throw new ArgumentNullException("set");
@@ -243,7 +247,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="item"></param>
 		/// <returns></returns>
-		public bool Add(T item)
+		public bool Add([NotNull] T item)
 		{
 // ReSharper disable CompareNonConstrainedGenericWithNull
 			if (item == null)
@@ -261,7 +265,7 @@ namespace ICD.Common.Utils.Collections
 		/// Adds the item to the collection.
 		/// </summary>
 		/// <param name="item"></param>
-		void ICollection<T>.Add(T item)
+		void ICollection<T>.Add([NotNull] T item)
 		{
 			Add(item);
 		}
@@ -270,7 +274,7 @@ namespace ICD.Common.Utils.Collections
 		/// Adds each of the items in the sequence to the collection.
 		/// </summary>
 		/// <param name="items"></param>
-		public void AddRange(IEnumerable<T> items)
+		public void AddRange([NotNull] IEnumerable<T> items)
 		{
 			if (items == null)
 				throw new ArgumentNullException("items");
@@ -293,7 +297,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="item"></param>
 		/// <returns></returns>
-		public bool Contains(T item)
+		public bool Contains([NotNull] T item)
 		{
 // ReSharper disable CompareNonConstrainedGenericWithNull
 			if (item == null)
@@ -307,8 +311,11 @@ namespace ICD.Common.Utils.Collections
 		/// Copies the items of the <see cref="T:System.Collections.Generic.ICollection`1"/> to an <see cref="T:System.Array"/>, starting at a particular <see cref="T:System.Array"/> index.
 		/// </summary>
 		/// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of the items copied from <see cref="T:System.Collections.Generic.ICollection`1"/>. The <see cref="T:System.Array"/> must have zero-based indexing.</param><param name="arrayIndex">The zero-based index in <paramref name="array"/> at which copying begins.</param><exception cref="T:System.ArgumentNullException"><paramref name="array"/> is null.</exception><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="arrayIndex"/> is less than 0.</exception><exception cref="T:System.ArgumentException"><paramref name="array"/> is multidimensional.-or-<paramref name="arrayIndex"/> is equal to or greater than the length of <paramref name="array"/>.-or-The number of items in the source <see cref="T:System.Collections.Generic.ICollection`1"/> is greater than the available space from <paramref name="arrayIndex"/> to the end of the destination <paramref name="array"/>.-or-Type T cannot be cast automatically to the type of the destination <paramref name="array"/>.</exception>
-		public void CopyTo(T[] array, int arrayIndex)
+		public void CopyTo([NotNull] T[] array, int arrayIndex)
 		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+
 			m_Dict.Keys.CopyTo(array, arrayIndex);
 		}
 
@@ -319,7 +326,7 @@ namespace ICD.Common.Utils.Collections
 		/// true if <paramref name="item"/> was successfully removed from the <see cref="T:System.Collections.Generic.ICollection`1"/>; otherwise, false. This method also returns false if <paramref name="item"/> is not found in the original <see cref="T:System.Collections.Generic.ICollection`1"/>.
 		/// </returns>
 		/// <param name="item">The object to remove from the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.</exception>
-		public bool Remove(T item)
+		public bool Remove([NotNull] T item)
 		{
 // ReSharper disable CompareNonConstrainedGenericWithNull
 			if (item == null)
@@ -333,7 +340,7 @@ namespace ICD.Common.Utils.Collections
 		/// Removes each of the items in the sequence from the collection.
 		/// </summary>
 		/// <param name="items"></param>
-		public void RemoveRange(IEnumerable<T> items)
+		public void RemoveRange([NotNull] IEnumerable<T> items)
 		{
 			if (items == null)
 				throw new ArgumentNullException("items");
@@ -352,6 +359,7 @@ namespace ICD.Common.Utils.Collections
 		/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
 		/// </returns>
 		/// <filterpriority>1</filterpriority>
+		[NotNull]
 		public IEnumerator<T> GetEnumerator()
 		{
 			return m_Dict.Keys.GetEnumerator();
@@ -364,6 +372,7 @@ namespace ICD.Common.Utils.Collections
 		/// An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.
 		/// </returns>
 		/// <filterpriority>2</filterpriority>
+		[NotNull]
 		IEnumerator IEnumerable.GetEnumerator()
 		{
 			return GetEnumerator();
diff --git a/ICD.Common.Utils/Collections/IcdOrderedDictionary.cs b/ICD.Common.Utils/Collections/IcdOrderedDictionary.cs
index 01c88b0..f02f894 100644
--- a/ICD.Common.Utils/Collections/IcdOrderedDictionary.cs
+++ b/ICD.Common.Utils/Collections/IcdOrderedDictionary.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using ICD.Common.Properties;
 using ICD.Common.Utils.Extensions;
 
 namespace ICD.Common.Utils.Collections
@@ -19,11 +20,14 @@ namespace ICD.Common.Utils.Collections
 
 		public bool IsReadOnly { get { return false; } }
 
+		[NotNull]
 		public ICollection<TKey> Keys { get { return m_OrderedKeys; } }
 
+		[NotNull]
 		public ICollection<TValue> Values { get { return m_ValuesOrderedByKey; } }
 
-		public TValue this[TKey key]
+		[CanBeNull]
+		public TValue this[[NotNull] TKey key]
 		{
 			get { return m_Dictionary[key]; }
 			set
@@ -51,7 +55,7 @@ namespace ICD.Common.Utils.Collections
 		/// Constructor.
 		/// </summary>
 		/// <param name="comparer"></param>
-		public IcdOrderedDictionary(IComparer<TKey> comparer)
+		public IcdOrderedDictionary([NotNull] IComparer<TKey> comparer)
 			: this(comparer, EqualityComparer<TKey>.Default)
 		{
 		}
@@ -61,7 +65,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="comparer"></param>
 		/// <param name="equalityComparer"></param>
-		public IcdOrderedDictionary(IComparer<TKey> comparer, IEqualityComparer<TKey> equalityComparer)
+		public IcdOrderedDictionary([NotNull] IComparer<TKey> comparer, [NotNull] IEqualityComparer<TKey> equalityComparer)
 		{
 			if (comparer == null)
 				throw new ArgumentNullException("comparer");
@@ -79,7 +83,7 @@ namespace ICD.Common.Utils.Collections
 		/// Constructor.
 		/// </summary>
 		/// <param name="dictionary"></param>
-		public IcdOrderedDictionary(IEnumerable<KeyValuePair<TKey, TValue>> dictionary)
+		public IcdOrderedDictionary([NotNull] IEnumerable<KeyValuePair<TKey, TValue>> dictionary)
 			: this()
 		{
 			if (dictionary == null)
@@ -91,16 +95,18 @@ namespace ICD.Common.Utils.Collections
 
 		#region Methods
 
+		[NotNull]
 		public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
 		{
 			return m_OrderedKeys.Select(k => new KeyValuePair<TKey, TValue>(k, m_Dictionary[k]))
 			                    .GetEnumerator();
 		}
 
-		public void Add(TKey key, TValue value)
+		public void Add([NotNull] TKey key, [CanBeNull] TValue value)
 		{
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("key");
 
 			if (m_Dictionary.ContainsKey(key))
@@ -119,15 +125,21 @@ namespace ICD.Common.Utils.Collections
 			m_Dictionary.Clear();
 		}
 
-		public bool ContainsKey(TKey key)
+		public bool ContainsKey([NotNull] TKey key)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			return m_Dictionary.ContainsKey(key);
 		}
 
-		public bool Remove(TKey key)
+		public bool Remove([NotNull] TKey key)
 		{
-// ReSharper disable once CompareNonConstrainedGenericWithNull
+// ReSharper disable CompareNonConstrainedGenericWithNull
 			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
 				throw new ArgumentNullException("key");
 
 			if (!m_Dictionary.Remove(key))
@@ -141,8 +153,13 @@ namespace ICD.Common.Utils.Collections
 			return true;
 		}
 
-		public bool TryGetValue(TKey key, out TValue value)
+		public bool TryGetValue([NotNull] TKey key, out TValue value)
 		{
+// ReSharper disable CompareNonConstrainedGenericWithNull
+			if (key == null)
+// ReSharper restore CompareNonConstrainedGenericWithNull
+				throw new ArgumentNullException("key");
+
 			return m_Dictionary.TryGetValue(key, out value);
 		}
 
@@ -150,6 +167,7 @@ namespace ICD.Common.Utils.Collections
 
 		#region Private Methods
 
+		[NotNull]
 		IEnumerator IEnumerable.GetEnumerator()
 		{
 			return GetEnumerator();
@@ -167,8 +185,11 @@ namespace ICD.Common.Utils.Collections
 			       EqualityComparer<TValue>.Default.Equals(value, item.Value);
 		}
 
-		void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int index)
+		void ICollection<KeyValuePair<TKey, TValue>>.CopyTo([NotNull] KeyValuePair<TKey, TValue>[] array, int index)
 		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+
 			foreach (KeyValuePair<TKey, TValue> kvp in this)
 			{
 				array.SetValue(kvp, index);
diff --git a/ICD.Common.Utils/Collections/PriorityQueue.cs b/ICD.Common.Utils/Collections/PriorityQueue.cs
index 8c07ef3..a772417 100644
--- a/ICD.Common.Utils/Collections/PriorityQueue.cs
+++ b/ICD.Common.Utils/Collections/PriorityQueue.cs
@@ -30,6 +30,7 @@ namespace ICD.Common.Utils.Collections
 		/// <summary>
 		/// Gets a reference for locking.
 		/// </summary>
+		[NotNull]
 		public object SyncRoot { get { return this; } }
 
 		#endregion
@@ -59,7 +60,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="item"></param>
 		[PublicAPI]
-		public void Enqueue(T item)
+		public void Enqueue([CanBeNull] T item)
 		{
 			Enqueue(item, int.MaxValue);
 		}
@@ -71,16 +72,10 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="item"></param>
 		/// <param name="priority"></param>
 		[PublicAPI]
-		public void Enqueue(T item, int priority)
+		public void Enqueue([CanBeNull] T item, int priority)
 		{
-			List<T> queue;
-			if (!m_PriorityToQueue.TryGetValue(priority, out queue))
-			{
-				queue = new List<T>();
-				m_PriorityToQueue.Add(priority, queue);
-			}
-
-			queue.Add(item);
+			m_PriorityToQueue.GetOrAddNew(priority, () => new List<T>())
+			                 .Add(item);
 			m_Count++;
 		}
 
@@ -89,18 +84,10 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="item"></param>
 		[PublicAPI]
-		public void EnqueueFirst(T item)
+		public void EnqueueFirst([CanBeNull] T item)
 		{
-			const int priority = int.MinValue;
-
-			List<T> queue;
-			if (!m_PriorityToQueue.TryGetValue(priority, out queue))
-			{
-				queue = new List<T>();
-				m_PriorityToQueue.Add(priority, queue);
-			}
-
-			queue.Insert(0, item);
+			m_PriorityToQueue.GetOrAddNew(int.MinValue, () => new List<T>())
+			                 .Insert(0, item);
 			m_Count++;
 		}
 
@@ -112,7 +99,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="item"></param>
 		/// <param name="remove"></param>
 		[PublicAPI]
-		public void EnqueueRemove(T item, Func<T, bool> remove)
+		public void EnqueueRemove([CanBeNull] T item, [NotNull] Func<T, bool> remove)
 		{
 			if (remove == null)
 				throw new ArgumentNullException("remove");
@@ -129,7 +116,7 @@ namespace ICD.Common.Utils.Collections
 		/// <param name="remove"></param>
 		/// <param name="priority"></param>
 		[PublicAPI]
-		public void EnqueueRemove(T item, Func<T, bool> remove, int priority)
+		public void EnqueueRemove([CanBeNull] T item, [NotNull] Func<T, bool> remove, int priority)
 		{
 			if (remove == null)
 				throw new ArgumentNullException("remove");
@@ -180,6 +167,7 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <returns></returns>
 		[PublicAPI]
+		[CanBeNull]
 		public T Dequeue()
 		{
 			T output;
@@ -227,6 +215,7 @@ namespace ICD.Common.Utils.Collections
 		/// Gets an enumerator for the items.
 		/// </summary>
 		/// <returns></returns>
+		[NotNull]
 		public IEnumerator<T> GetEnumerator()
 		{
 			return m_PriorityToQueue.Values
@@ -239,8 +228,11 @@ namespace ICD.Common.Utils.Collections
 		/// </summary>
 		/// <param name="array"></param>
 		/// <param name="index"></param>
-		public void CopyTo(Array array, int index)
+		public void CopyTo([NotNull] Array array, int index)
 		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+
 			foreach (T item in this)
 				array.SetValue(item, index++);
 		}
@@ -253,6 +245,7 @@ namespace ICD.Common.Utils.Collections
 		/// Gets an enumerator for the items.
 		/// </summary>
 		/// <returns></returns>
+		[NotNull]
 		IEnumerator IEnumerable.GetEnumerator()
 		{
 			return GetEnumerator();
diff --git a/ICD.Common.Utils/Collections/RateLimitedEventQueue.cs b/ICD.Common.Utils/Collections/RateLimitedEventQueue.cs
index dc4708e..b3cc5bb 100644
--- a/ICD.Common.Utils/Collections/RateLimitedEventQueue.cs
+++ b/ICD.Common.Utils/Collections/RateLimitedEventQueue.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using ICD.Common.Properties;
 using ICD.Common.Utils.EventArguments;
 using ICD.Common.Utils.Extensions;
 using ICD.Common.Utils.Timers;
@@ -32,6 +33,7 @@ namespace ICD.Common.Utils.Collections
 
 		bool ICollection.IsSynchronized { get { return true; } }
 
+		[NotNull]
 		object ICollection.SyncRoot { get { return this; } }
 
 		#endregion
@@ -72,7 +74,7 @@ namespace ICD.Common.Utils.Collections
 		/// Enqueues the given item.
 		/// </summary>
 		/// <param name="item"></param>
-		public void Enqueue(T item)
+		public void Enqueue([CanBeNull] T item)
 		{
 			m_QueueSection.Enter();
 
@@ -158,18 +160,23 @@ namespace ICD.Common.Utils.Collections
 
 		#region IEnumerable/ICollection
 
+		[NotNull]
 		public IEnumerator<T> GetEnumerator()
 		{
 			return m_QueueSection.Execute(() => m_Queue.ToList(m_Queue.Count).GetEnumerator());
 		}
 
+		[NotNull]
 		IEnumerator IEnumerable.GetEnumerator()
 		{
 			return GetEnumerator();
 		}
 
-		void ICollection.CopyTo(Array array, int index)
+		void ICollection.CopyTo([NotNull] Array array, int index)
 		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+
 			m_QueueSection.Enter();
 
 			try