crystal report error

ReportDocument rptDoc = new ReportDocument();
   DataSet1 ds1 = new DataSet1(); // .xsd file name
   DataTable dt = new DataTable();

   // Just set the name of data table
   dt.TableName = "bill";
   dt = getAllOrders(); //This function is located below this function
   ds1.Tables[0].Merge(dt);<<<<<<getting error here : .column1 and .column1 have conflicting properties: DataType property mismatch.>>>>>>>

   // Your .rpt file path will be below
   rptDoc.Load(Server.MapPath("../WebSite2/CrystalReport.rpt"));

   //set dataset to the report viewer.
   rptDoc.SetDataSource(ds1);
   CrystalReportViewer1.ReportSource = rptDoc;



public DataTable getAllOrders()
   {
       //Connection string replace 'databaseservername' with your db server name
       string sqlCon = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\Apps\WebSite2\Database21.accdb;Persist Security Info=False;";
       OleDbConnection Con = new OleDbConnection(sqlCon);
       OleDbCommand cmd = new OleDbCommand();
       DataSet ds = null;
       OleDbDataAdapter adapter;
       try
       {
           Con.Open();
           cmd = Con.CreateCommand();
           cmd.CommandType = CommandType.Text;
           cmd.CommandText = "select *from bill";
           ds = new DataSet();
           adapter = new OleDbDataAdapter(cmd);
           adapter.Fill(ds, "bill");
           cmd.ExecuteNonQuery();
       }