Cannot implicitly convert type 'string' to 'bool'

I am trying to test a textbox variable for data.  To the best of my knowledge, the text box has never been defined as a bool object.  Can someone tell me what I am missing.  Here is my code:



string clinical_pass = " ";

        if (Session.Contents["clinical_pass"] != null)
        {
            clinical_pass = Session.Contents["clinical_pass"].ToString();
        }




if (tbClinicalPassword.Text = clinical_pass)   --------------------------   error occurs here
        {
            // Do Stuff

        }
        else
            lblError.Text = "Invalid Password";Start Free Trial