DataTable ds = new DataTable();
ds.Columns.Add("Email", typeof(string));
ds.Rows.Add("email1@domain.com");
ds.Rows.Add("email2@domain.com");
ds.Rows.Add("email3@domain.com");
string emailList = ds.Select()
.Select(r => (string)r["Email"])
.Aggregate((a, b) => a = a + ";" + b);
in the above emailList will now contain a list of all email addresses separated by semi-colons.