how to select particular columns in sql statement

This is probably something that is best left to a reporting tool like SQL Server Reporting Services, Crystal Reports, etc. However, if it needs to get done and you are not using a reporting tool then it is at least possible.

On the C# side you might be able to remove the columns from the underlying DataTable in the DataSet by cycling through the Columns collection of the DataTable. This would require looking at both rows for each field (or using a Linq query) and then removing the Column. I have not tried this so I am not sure of the effectiveness of it or how easy/complicated it would be. You can find more details about the DataTable structure here:

http://msdn.microsoft.com/en-us/library/system.data.datatable.columns.aspx

If you have the option of calling a Stored Procedure, you can do the multi-step operation that @Mikael suggested in the first comment on the question. Here is how I would approach this from the T-SQL side:

CREATE TABLE #TempResults ([Date] VARCHAR(30), Machine VARCHAR(50),
    [A] INT, [B] INT, [C] INT, [D] INT, [E] INT, [F] INT, [G] INT,
    [OTHERS] INT)

INSERT INTO #TempResults ([Date], Machine, A, B, C, D, E, F, G, OTHERS)
    SELECT  DateString AS [Date],
            machine, 
        SUM(CASE WHEN vfrm.job_id = '105' THEN (total_hours) ELSE '0' END) AS [A],
        SUM(CASE WHEN vfrm.job_id = '100' THEN (total_hours) ELSE '0' END) AS [B],
        SUM(CASE WHEN vfrm.job_id = '101' THEN (total_hours) ELSE '0' END) AS [C],
        SUM(CASE WHEN vfrm.job_id = '102' THEN (total_hours) ELSE '0' END) AS [D],
        SUM(CASE WHEN vfrm.job_id = '103' THEN (total_hours) ELSE '0' END) AS [E],
        SUM(CASE WHEN vfrm.job_id = '134' THEN (total_hours) ELSE '0'  END) AS [F],
        SUM(CASE WHEN vfrm.job_id = '135' THEN (total_hours) ELSE '0' END) AS [G],
        SUM(CASE WHEN vfrm.job_id = '9995' THEN (total_hours) ELSE '0' END) AS [OTHERS]
    FROM    ven_fullreportmaster vfrm
    INNER JOIN  ven_descriptionmaster vdm
            ON  vdm.description_id = vfrm.description_id
    INNER JOIN  ven_machinemaster vm
            ON  vm.machine_id = vfrm.machine_id
    INNER JOIN  ven_jobcodemaster vjm
            ON  vjm.job_id = vfrm.job_id
    INNER JOIN  Dim_Time dt
            ON  dt.Date_Id = vfrm.date_id
    WHERE   vfrm.entry_date = '20111208'
    AND     vfrm.shift_id = 2
    AND     vfrm.description_id IN (1, 3, 5)
    AND     vfrm.job_id NOT IN (9999, 9998, 9996, 9994)
    AND     vjm.job_status = 'ACTIVE'
    GROUP BY    description_name, DateString

DECLARE @SQL NVARCHAR(MAX)

SET @SQL = N'SELECT [Date], Machine, '

IF (EXISTS (SELECT * FROM #TempResults WHERE [A] > 0))
BEGIN
    SET @SQL = @SQL + N'[A], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [B] > 0))
BEGIN
    SET @SQL = @SQL + N'[B], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [C] > 0))
BEGIN
    SET @SQL = @SQL + N'[C], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [D] > 0))
BEGIN
    SET @SQL = @SQL + N'[D], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [E] > 0))
BEGIN
    SET @SQL = @SQL + N'[E], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [F] > 0))
BEGIN
    SET @SQL = @SQL + N'[F], '
END

IF (EXISTS (SELECT * FROM #TempResults WHERE [G] > 0))
BEGIN
    SET @SQL = @SQL + N'[G], '
END

SET @SQL = @SQL + N'[OTHERS] FROM #TempResults'

EXEC (@SQL)
GO

P.S. There seems to be an issue with your GROUP BY clause as I would expect the [Machine] field to be required in it.