I am trying to get a return value and it keeps giving me an error. I am trying to grab the "roleid" after the username has been validated by sending it the username-- I can't figure out what I am doing wrong?

 public string ValidateRole(string sUsername)
   {

       string matchstring = "SELECT  roleid FROM tblUserRoles WHERE UserName='" +      sUsername +"'";
       SqlCommand cmd = new SqlCommand(matchstring);
       cmd.Connection = new SqlConnection("Data Source=(local);Initial Catalog="mydatabase";Integrated Security=True");
       cmd.Connection.Open();
       cmd.CommandType = CommandType.Text;

       SqlDataAdapter sda = new SqlDataAdapter();
       DataTable dt = new DataTable();
       sda.SelectCommand = cmd;
       sda.Fill(dt);

       string match;
    if (dt.Rows.Count > 0)
    {
       foreach (DataRow row in dt.Rows)
       {
           match = row["roleid"].ToString();
        return match;
       }              

    }  
          else
    {  
        match = "fail";
          return match;
       }

   }