sorting on merged datasets

I have merged two datasets but now need to sort on the dtmappt so that the dates display correctly.  How can I sort on a merged dataset please?

thanks

MyCommand = New SqlDataAdapter("SELECT  a.APPTDATE as apptdate, a.APPTREASON AS apptreason  FROM tblPSPatient s INNER JOIN HealthDistrict.dbo.DDB_PAT_BASE p ON s.lngPatientid = p.CHART INNER JOIN HealthDistrict.dbo.DDB_APPT_BASE a ON p.PATID = a.PATID  where lngPSPatientid = '" & patid & "'and a.apptdate > '" & brokendate & "'  ORDER BY s.lngPSPatientid, a.APPTDATE", Connection1)
            DS1 = New DataSet
            MyCommand.Fill(DS1, "MyTable")
 
            MyCommand = New SqlDataAdapter("SELECT d.dtmScreening as apptdate,   'Project Smile Screening' AS apptreason FROM HealthDistrict.dbo.tblDentalScreening d INNER JOIN HealthDistrict.dbo.tblPatient p ON d.lngPatientid = p.lngPatientId LEFT OUTER JOIN tblPSPatient pat ON p.strLName = pat.strlname AND p.strFName = pat.strfname AND p.strPatientId = pat.lngPatientid  where lngPSPatientid = '" & patid & "' ", Connection1)
            DS2 = New DataSet
            MyCommand.Fill(DS2, "MyTable")
 
 
            ds1.merge(ds2)

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