diff --git a/BTree.cs b/BTree.cs
index e15fdab..d3c89ec 100644
--- a/BTree.cs
+++ b/BTree.cs
@@ -160,19 +160,19 @@ namespace ln.collections
 			if (node != null)
 				return node.Value;
 			throw new KeyNotFoundException("BTree is empty");
-		}
-        public bool TryGetFirstValue(out V value)
-        {
-            TreeNode node = First(headNode);
-            if (node != null)
-            {
-                value = node.Value;
-                return true;
-            }
-            value = default(V);
-            return false;
-        }
-
+		}
+        public bool TryGetFirstValue(out V value)
+        {
+            TreeNode node = First(headNode);
+            if (node != null)
+            {
+                value = node.Value;
+                return true;
+            }
+            value = default(V);
+            return false;
+        }
+
         public K Last()
 		{
 			TreeNode node = Last(headNode);
@@ -187,16 +187,16 @@ namespace ln.collections
 				return node.Value;
 			throw new KeyNotFoundException("BTree is empty");
 		}
-        public bool TryGetLastValue(out V value)
-        {
-            TreeNode node = Last(headNode);
-            if (node != null)
-            {
-                value = node.Value;
-                return true;
-            }
-            value = default(V);
-            return false;
+        public bool TryGetLastValue(out V value)
+        {
+            TreeNode node = Last(headNode);
+            if (node != null)
+            {
+                value = node.Value;
+                return true;
+            }
+            value = default(V);
+            return false;
         }
 
 		public K Previous(K current)
@@ -206,24 +206,24 @@ namespace ln.collections
                 return node.Key;
             throw new KeyNotFoundException();
         }
-        public bool TryGetPrevious(K current, out K previous)
-        {
+        public bool TryGetPrevious(K current, out K previous)
+        {
             TreeNode node = Previous(Find(current));
-            if (node != null)
-            {
+            if (node != null)
+            {
                 previous = node.Key;
-                return true;
+                return true;
             }
             previous = default(K);
             return false;
         }
-        public bool TryGetPreviousValue(K current, out V previous)
-        {
+        public bool TryGetPreviousValue(K current, out V previous)
+        {
             TreeNode node = Previous(Find(current));
-            if (node != null)
-            {
+            if (node != null)
+            {
                 previous = node.Value;
-                return true;
+                return true;
             }
             previous = default(V);
             return false;
@@ -236,29 +236,67 @@ namespace ln.collections
                 return node.Key;
             throw new KeyNotFoundException();
         }
-        public bool TryGetNext(K current, out K next)
-        {
+        public bool TryGetNext(K current, out K next)
+        {
             TreeNode node = Next(Find(current));
-            if (node != null)
-            {
+            if (node != null)
+            {
                 next = node.Key;
-                return true;
+                return true;
             }
             next = default(K);
             return false;
         }
-        public bool TryGetNextValue(K current, out V next)
-        {
+        public bool TryGetNextValue(K current, out V next)
+        {
             TreeNode node = Next(Find(current));
-            if (node != null)
-            {
+            if (node != null)
+            {
                 next = node.Value;
-                return true;
+                return true;
             }
             next = default(V);
             return false;
         }
 
+        public K PreviousOrCurrent(K current)
+        {
+            if (!TryGetPreviousOrCurrent(current, out K previousOrCurrent))
+                throw new KeyNotFoundException();
+            return previousOrCurrent;
+        }
+        public bool TryGetPreviousOrCurrent(K current, out K previousOrCurrent)
+        {
+            if (Empty)
+            {
+                previousOrCurrent = default(K);
+                return false;
+            }
+
+            TreeNode next = FindFirstGE(current);
+            if (next == null)
+                previousOrCurrent = Last();
+            else
+                previousOrCurrent = Previous(next).Key;
+
+            return true;
+        }
+        public bool TryGetPreviousOrCurrentValue(K current, out V previousOrCurrentValue)
+        {
+            if (Empty)
+            {
+                previousOrCurrentValue = default(V);
+                return false;
+            }
+
+            TreeNode next = FindFirstGE(current);
+            if (next == null)
+                previousOrCurrentValue = LastValue();
+            else
+                previousOrCurrentValue = Previous(next).Value;
+
+            return true;
+        }
 
 
 
@@ -302,7 +340,7 @@ namespace ln.collections
         {
             TreeNode node = headNode;
             TreeNode minNode = null;
-
+            
             while (node != null)
             {
                 if ((Comparison(node.Key, key) >= 0) && ((minNode == null) || (Comparison(node.Key, minNode.Key) < 0)))