Scenario: You need to fit a dentist appointment into an already-packed schedule. The Dentist has given you a list of dates this month where he can fit you in. Use the following query to determine which dates work for both of you.
Public Sub Linq107()
Randomize()
Dim y = Year(Now)
Dim m = Month(Now)
'Randomly pick 15 appointment dates this month
Dim DentistDates(15) As Date, AvailableDates(8) As Date
For i = 0 To UBound(DentistDates)
DentistDates(i) = New Date(y, m, Int(Date.DaysInMonth(y, m) * Rnd() + 1))
Next
'Randomly pick 8 dates you're free this month
For i = 0 To UBound(AvailableDates)
AvailableDates(i) = New Date(y, m, Int(Date.DaysInMonth(y, m) * Rnd() + 1))
Next
Dim CommonDates = From _
d In AvailableDates, d2 In DentistDates _
Where d.Date = d2.Date _
Select d _
Distinct _
Order By d
'Just to make it easier to see that the query works, we sort the original lists before display
Array.Sort(DentistDates)
Array.Sort(AvailableDates)
Console.WriteLine("Dentist is free on:")
ObjectDumper.Write(DentistDates)
Console.WriteLine(vbNewLine & "You are free on:")
ObjectDumper.Write(AvailableDates)
Console.WriteLine(vbNewLine & "Appointment dates that work:")
For Each d In CommonDates
Console.WriteLine(Format(d, "MM/dd/yy"))
Next
End Sub
Result:
Dentist is free on:
8/1/2007
8/2/2007
8/2/2007
8/6/2007
8/10/2007
8/11/2007
8/12/2007
8/13/2007
8/14/2007
8/17/2007
8/23/2007
8/25/2007
8/26/2007
8/28/2007
8/31/2007
8/31/2007
You are free on:
8/1/2007
8/2/2007
8/8/2007
8/10/2007
8/12/2007
8/15/2007
8/20/2007
8/28/2007
8/29/2007
Appointment dates that work:
08/01/07
08/02/07
08/10/07
08/12/07
08/28/07
This query determines the top 5 memory-using applications currently loaded.
Public Sub Linq108()
Dim pList = From p In System.Diagnostics.Process.GetProcesses() _
Select ProcessName = p.ProcessName, _
Size = (Format(p.WorkingSet64 / 1000, "#,##0") & " KB"), _
Size64 = p.WorkingSet64 _
Order By Size64 Take 5
Console.WriteLine("These 5 processes are using the most memory:")
For Each p In pList
Console.WriteLine(p.ProcessName & " - " & p.Size)
Next
End Sub
Result:
These 5 processes are using the most memory:
Idle - 16 KB
System - 217 KB
smss - 381 KB
lsass - 934 KB
vpcmap - 958 KB
This query finds hidden files in a given directory.
Public Sub Linq109()
Dim fileList = From f In New DirectoryInfo("C:\").GetFiles() _
Where (f.Attributes And FileAttributes.Hidden) = FileAttributes.Hidden _
Order By f.Name
Console.WriteLine("Hidden Files:")
For Each f In fileList
Console.WriteLine(f.Name)
Next
End Sub
Result:
Hidden Files:
boot.ini
IO.SYS
MSDOS.SYS
NTDETECT.COM
ntldr
pagefile.sys
This query finds files created within the last year.
Public Sub Linq110()
Dim fileList = From f In New DirectoryInfo("C:\").GetFiles() _
Where f.CreationTime.AddYears(1) > Now _
Select f _
Order By f.Name
Console.WriteLine("Files created within the last year:")
For Each f In fileList
Console.WriteLine(f.Name)
Next
End Sub
Result:
Files created within the last year:
VB101LINQQuerySamples_Content.zip
VB101LINQQuerySamples_Content_ByCategory.zip
VB101LINQQuerySamples_Content_SeparatePages.zip
This query shows all mapped network drives
Public Sub Linq111()
'If you want to see other drive types (i.e. CDRom) please change the enum below
Dim Drives = From d In My.Computer.FileSystem.Drives() _
Where d.DriveType = System.IO.DriveType.Network _
Select d
Console.WriteLine("Network Drives:")
For Each d In Drives
Console.WriteLine(d.Name)
Next
End Sub
Result:
Network Drives:
Uses LINQ to check for the /help command line argument.
Public Sub Linq112()
'To experiment with this you can double-click My Project, click on Debug and
'enter /help in the command line arguments textbox
Dim cmdArgs = (From c In My.Application.CommandLineArgs() _
Where c = "/help" _
Select c).Count()
If cmdArgs = 0 Then
Console.WriteLine("""/help"" was not entered as a command line argument.")
Else
Console.WriteLine("""/help"" requested by user on the command line.")
End If
End Sub
Result:
"/help" was not entered as a command line argument.
Shows all keys under HKLM\Software that start with the letter C.
Public Sub Linq113()
Dim SubKeys = _
My.Computer.Registry.LocalMachine.OpenSubKey("Software").GetSubKeyNames
Dim reg = From r In SubKeys _
Where r.StartsWith("C") _
Order By r
ObjectDumper.Write(reg)
End Sub
Result:
C07ft5Y
Classes
Clients
ComputerAssociates
Shows keys common to HKLM\Software and HKCU\Software
Public Sub Linq114()
Dim LMKeys = _
My.Computer.Registry.LocalMachine.OpenSubKey("Software").GetSubKeyNames
Dim UserKeys = _
My.Computer.Registry.CurrentUser.OpenSubKey("Software").GetSubKeyNames
'Performs an intersection on the two arrays
Dim reg = From LocalMachineKey In LMKeys, UserKey In UserKeys _
Where LocalMachineKey = UserKey _
Select LocalMachineKey, UserKey _
Order By LocalMachineKey
Console.WriteLine("Keys common to HKLM\Software and HKCU\Software:")
For Each r In reg
Console.WriteLine(r.LocalMachineKey)
Next
End Sub
Result:
Keys common to HKLM\Software and HKCU\Software:
Classes
Microsoft
ODBC
Policies
Shows shortcuts to everything under "My Recent Documents"
Public Sub Linq115()
Dim RecentPath As String = _
Environment.GetFolderPath(Environment.SpecialFolder.Recent)
'Uses an anonymous type to reduce the amount of information returned
Dim Recent = From r In New DirectoryInfo(RecentPath).GetFiles _
Select r.Name, r.LastAccessTime
Console.WriteLine("Shortcuts to My Recent Documents:")
For Each r In Recent
Console.WriteLine("{0,-45}{1}", r.Name, r.LastAccessTime)
Next
End Sub
Result:
Shortcuts to My Recent Documents:
Desktop.ini 8/13/2007 9:04:44 PM
LINQQuerySamples_aggregateoperators.html.lnk 8/13/2007 10:25:29 PM
LINQSamples.lnk 8/13/2007 10:40:05 PM
LINQtoSQLSamples_insertupdatedelete.html.lnk 8/13/2007 10:25:14 PM
TOC.html.lnk 8/13/2007 10:40:05 PM
Counts how many items are in your Favorites folder
Public Sub Linq116()
Dim FavPath As String = Environment.GetFolderPath(Environment.SpecialFolder.Favorites)
Dim FavSize = (From f In New DirectoryInfo(FavPath).GetFiles() _
Select f).Count()
Console.WriteLine("There are {0} files in your Favorites folder.", FavSize)
End Sub
Result:
There are 3 files in your Favorites folder.
