C# string to var data type
===

How can i change from data type from string to var ?
Example:

    private void button1_Click(object sender, EventArgs e)
        {
            work("checkBox1");
        }

        public void work(string check)
        {

        string number = "1";
                if (number == "1")
                {
                    check.Checked = true;
                    MessageBox.Show("True");
                }
                else
                {
                    check.Checked = false;
                    MessageBox.Show("False");
                }
       
        }

How can i solve this problem 
<code>'string' does not contain a definition for 'Checked' and no extension method 'Checked' accepting</code>

But i want, to 
 work button insert checkbox name