.NET (Core and Framework)

using (var connection = new SqlConnection("..."))
using (var command = new SqlCommand("... PO_Date Between @FromDate And @ToDate ...", connection))
{
    command.Parameters.AddWithValue("@FromDate", dtfrom.Value);
    command.Parameters.AddWithValue("@ToDate", dtto.Value);
    ...
}

WITH ctePurchases As
(
    SELECT
        Item,
        Sum(Quantity_Received) As Quantity_Received
    FROM
        Purchase
    WHERE
        PO_Date Between @FromDate And @ToDate
    GROUP BY
        Item
),
cteSales As
(
    SELECT
        Item_Description,
        Sum(Quantity) As Quantity
    FROM
        Sales
    WHERE
        Sales_Date Between @FromDate And @ToDate
    GROUP BY
        Item_Description
)
SELECT
    IsNull(P.Item, S.Item_Description) As Item,
    IsNull(P.Quantity_Received, 0) As Purchases,
    IsNull(S.Quantity, 0) As Sold
FROM
    ctePurchases As P
    FULL OUTER JOIN cteSales As S
    ON S.Item_Description = P.Item
;

WITH ctePurchases As...

ratchoy010 wrote:

By the way, i'm using vb.net 2008 with MS Access as my database back-end.

SELECT
    IsNull(P.Item, S.Item_Description) As Item,
    IsNull(P.Quantity_Received, 0) As Purchases,
    IsNull(S.Quantity, 0) As Sold
FROM
    (
        SELECT
            Item,
            Sum(Quantity_Received) As Quantity_Received
        FROM
            Purchase
        WHERE
            PO_Date Between ? And ?
        GROUP BY
            Item
    ) As P
    FULL OUTER JOIN 
    (
        SELECT
            Item_Description,
            Sum(Quantity) As Quantity
        FROM
            Sales
        WHERE
            Sales_Date Between ? And ?
        GROUP BY
            Item_Description
    ) As S
    ON S.Item_Description = P.Item

using (var connection = new OleDbConnection("..."))
using (var command = new OleDbCommand("...", connection))
{
    // The names don't matter here, only the order:
    command.Parameters.AddWithValue("p0", dtfrom.Value);
    command.Parameters.AddWithValue("p1", dtto.Value);
    
    // You have to repeat the parameters, since they appear twice in the query:
    command.Parameters.AddWithValue("p2", dtfrom.Value);
    command.Parameters.AddWithValue("p3", dtto.Value);
    ...
}

using System;
using System.Management;
using System.Windows.Forms;

namespace WMISample
{
    public class MyWMIQuery
    {
        public static void Main()
        {
            try
            {
                 ManagementObjectSearcher searcher =
                    new ManagementObjectSearcher("root\\CIMV2",
                    "SELECT * FROM Win32_Service");

                ManagementObjectSearcher procsearcher =
                    new ManagementObjectSearcher("root\\CIMV2",
                    "SELECT * FROM Win32_Process");
                String q;

                foreach (ManagementObject queryObj in searcher.Get())
                {
                    if (queryObj["ProcessId"].ToString() != "0")
                    {
                    Console.WriteLine("-----------------------------------");
                                        
                    q = "SELECT * FROM Win32_Process WHERE ProcessId=";
                    q += queryObj["ProcessId"].ToString();

                    procsearcher.Query = new System.Management.ObjectQuery(q);

                    foreach (ManagementObject ProcObj  in procsearcher.Get())
                    {
                        Console.WriteLine("Name: {0} : {1}", queryObj["Name"], ProcObj["WorkingSetSize"]);
                    }
                    }
                }
            }
            catch (ManagementException e)
            {
                MessageBox.Show("An error occurred while querying for WMI data: " + e.Message);
            }
        }
    }
}