Created 'Add' function for Binary Search Tree

C#/Datastructures/BinarySearchTree/Tree.cs

@@ -5,21 +5,74 @@ namespace C_.Datastructures.BinarySearchTree
 {
     internal class Tree<T> where T:IComparable
     {
-        public TreeNode<T>? Head { get; set; }
+        public TreeNode<T>? Root { get; set; }
         public int Count { get; set; }
 
         public Tree<T> Create(){
             //Create a new Tree with no Head
             return new Tree<T>{
-                Head = null,
+                Root = null,
                 Count = 0
             };
         }
         public Tree<T> Create(T? value){
             //Create a new Tree with Head
             return new Tree<T>{
-                Head = TreeNode<T>.Create(value)
+                Root = TreeNode<T>.Create(value)
             };
         }
+
+        public void Add(T value)
+        {//Add item to the correct position in the tree (Input cannot be null)
+            Count++;
+
+            if (Root == default)
+            {//If new node should become the root
+                Root = TreeNode<T>.Create(value);
+                return;
+            }
+
+            //Find position to insert
+            TreeNode<T> node = Root;
+            node = Descend(value, node)!;
+
+            if (value.CompareTo(node.Value) < 0)
+            {//Insert to left
+                node.Left = TreeNode<T>.Create(value);
+                return;
+            }
+            //Insert to right
+            node.Right = TreeNode<T>.Create(value);
+            return;
+
+            
+        }
+
+        private TreeNode<T>? Descend(T value, TreeNode<T>? current)
+        {//Keep trying to determine whether to go left or right until null node is found
+            if (current == default)
+                return default;
+
+            TreeNode<T>? node;
+
+            if (value.CompareTo(current.Value) < 0)
+            {//Descend left
+                node = Descend(value, current.Left);
+                if (node == null)
+                {
+                    return current;
+                }
+                return node; 
+            }
+            else
+            {//Descend right
+                node = Descend(value, current.Right);
+                if (node == null)
+                {
+                    return current;
+                }
+                return node;
+            }
+        }
     }
 }