Error Cannot Implicitly Convert DataSet To String

This is my syntax and I realize that I am trying to assign a DataSet to a string variable, but this is what I need to do.  How can I re-assign / re-code this in order to achieve what I am after?
I need chosenEmployees = barf ..... string value to = DataSet

namespace Lalala.Pages { public partial class Page1 : System.Web.UI.Page { private string employeesToIterate; private string chosenEmployees; private DataSet barf = new DataSet(); private ArrayList empList = new ArrayList(); private string[] emp; private void btn13_Click() { barf = RunThisMethod(); AlphaDawg(); } private DataSet RunThisMethod() { //stuff here to run a SQL Query return barf; } private void AlphaDawg() { //Below Line Is The Culprit chosenEmployees = barf; emp = chosenEmployees.Split(' '); empList.AddRange(emp); } } }