This is a continuation of my post How to create a binary tree in c#.In this post, I will show you how to find the size of the binary tree.

Size of the binary tree is the number of nodes in a given tree.

**Following is the recursive implementation of size function**

```
//Compute the number of nodes in a tree.
public int Size()
{
return Size(_root);
}
private int Size(Node root)
{
if (root == null)
return 0;
return 1 + Size(root.Left) + Size(root.Right);
}
```