How to make more objects null

        private void button01_Click(object sender, EventArgs e)
        {
            Controls.Clear();            InitializeButtons();
            // ClearALLControls();
        } 

        private void button02_Click(object sender, EventArgs e)
        {
            Controls.Clear();            InitializeButtons();
        }

        private void button03_Click(object sender, EventArgs e)
        {
            Controls.Clear();            InitializeButtons();
        }


        void ClearALLControls() //this method not working - got 2 errors
        {
            foreach (Control item in this.Controls)
            {
                item = null; //error@ [item]
//Cannot assign to 'item' because it is a 'foreach iteration variable'	

            }
//so... it's a foreach problem? i try it with for loop then

            for (int i = 0; i < Controls.Count; i++)
            {
                Controls[i] = null; //error@ [Controls[i]]
//System.Windows.Forms.Control.ControlCollection.this[int]' cannot be assigned to -- it is read only	
            }
        }