The type or namespace name 'boolean' could not be found
<p>For the following code in my home work shows an error The type or namespace name 'boolean' could not be found</p>

<pre><code>          class LinkedList
   {
private Node first;
public LinkedList()
{
    first = null;
}
public boolean isEmpty()
{
    return (first == null);
}
public void insert(int val)//inserts at beginning of list
{
    Node newNode = new Node(val);
    newNode.next = first;
    first = newNode;
}
public Node delete()//deletes at beginning of list
{
    Node temp = first;
    first = first.next;
    return temp;
}
</code></pre>

<p>Every where on the internet i found almost similar question but are not exactly for boolean,
Someone please help me out.  By the way i am learning c# for 3-4 says.</p>
