My.Computer

My.Computer provides methods to understand and control the computer’s hardware and the system software. It lets you work with the audio system, clock, keyboard, clipboard, mouse, network, printers, registry, and file system.

The following sections describe the properties, methods, and events available through My.Computer in detail.

Audio

This object provides access to the computer’s audio system. Its methods let you play a .wav file synchronously or asynchronously, stop a file playing asynchronously, or play a system sound. For example, the following code plays the system’s exclamation sound:

  My.Computer.Audio.PlaySystemSound(SystemSounds.Exclamation) 

The following table describes the Audio object’s methods.

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Method	Purpose
Play	Plays .wav data from a file, byte array, or stream. The second parameter can be Background (play asynchronously in the background), BackgroundLoop (play asynchronously in the background and repeat when it ends), or WaitToComplete (play synchronously).
PlaySystemSound	Plays a system sound. The parameter should be a member of the SystemSounds enumeration and can have the value Asterisk, Beep, Exclamation, Hand, or Question.
Stop	Stops the sound currently playing asynchronously.

Clipboard

The Clipboard object described in Chapter 13 enables you to move data in and out of the system’s clipboard. The My.Computer.Clipboard object provides extra tools that simplify some clipboard operations. The following table briefly summarizes the My.Computer.Clipboard object’s methods.

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Method	Purpose
Clear	Removes all data from the clipboard.
ContainsAudio	Returns True if the clipboard contains audio data.
ContainsData	Returns True if the clipboard contains data in a specific custom format.
ContainsFileDropList	Returns True if the clipboard contains a file drop list.
ContainsImage	Returns True if the clipboard contains image data.
ContainsText	Returns True if the clipboard contains textual data.
GetAudioStream	Gets audio data from the clipboard.
GetData	Gets data in a specific custom format from the clipboard.
GetDataObject	Gets a DataObject from the clipboard.
GetFileDropList	Gets a StringCollection holding the names of the files selected for drop from the clipboard.
GetImage	Gets image data from the clipboard.
GetText	Gets textual data from the clipboard.
SetAudio	Saves audio data to the clipboard.
SetData	Saves data in a specific custom format to the clipboard.
SetDataObject	Saves a DataObject to the clipboard.
SetFileDropList	Saves a StringCollection containing a series of fully qualified file names to the clipboard.
SetImage	Saves an image to the clipboard.
SetText	Saves textual data to the clipboard.

See Chapter 13 for more information about using the clipboard.

Clock

This property returns an object of type MyClock that you can use to learn about the current time. The following table describes this object’s properties.

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Property	Purpose
GmtTime	Returns a Date object that gives the current local date and time converted into Coordinated Universal Time (UTC) or Greenwich Mean Time (GMT).
LocalTime	Returns a Date object that gives the current local date and time.
TickCount	Returns the number of milliseconds since the computer started.

For example, suppose that you live in Colorado, which uses Mountain Standard Time (MST), seven hours behind Greenwich Mean Time. If My.Computer.Clock.LocalTime returns 2:03 P.M., then My.Computer.Clock.GmtTime returns 9:03 P.M.

If you must store a date and time for later use (for example, in a database), you should generally store it in UTC. Then you can meaningfully compare that value with other times stored on other computers in different time zones such as those across the Internet.

FileSystem

The FileSystem object provides tools for working with drives, directories, and files. The following table summarizes this object’s properties and methods.

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Item	Description
CombinePath	Returns a properly formatted combined path as a string.
CopyDirectory	Copies a directory.
CopyFile	Copies a file.
CreateDirectory	Creates a directory.
CurrentDirectory	Determines the fully qualified path to the application’s current directory.
DeleteDirectory	Deletes a directory.
DeleteFile	Deletes a file.
DirectoryExists	Returns a Boolean indicating whether a directory exists.
Drives	Returns a read-only collection of DriveInfo objects describing the system’s drives. See Chapter 29 for information about the DriveInfo class.
FileExists	Returns a Boolean indicating whether a file exists.
FindInFiles	Returns a collection holding names of files that contain a search string.
GetDirectories	Returns a String collection representing the path names of subdirectories within a directory.
GetDirectoryInfo	Returns a DirectoryInfo object for the specified path.
GetDriveInfo	Returns a DriveInfo object for the specified path.
GetFileInfo	Returns a FileInfo object for the specified path.
GetFiles	Returns a read-only String collection representing the names of files within a directory.
GetParentPath	Returns a string representing the absolute path of the parent of the provided path.
MoveDirectory	Moves a directory.
MoveFile	Moves a file.
OpenTextFieldParser	Opens a TextFieldParser.
OpenTextFileReader	Opens a TextReader.
OpenTextFileWriter	Opens a TextWriter.
ReadAllBytes	Reads from a binary file.
ReadAllText	Reads from a text file.
RenameDirectory	Renames a directory.
RenameFile	Renames a file.
SpecialDirectories	Returns a SpecialDirectoriesProxy object that has properties giving the locations of various special directories such as the system’s temporary directory and the user’s MyDocuments directory. See Chapter 29 for more information.
WriteAllBytes	Writes to a binary file.
WriteAllText	Writes to a text file.

Info

The My.Computer.Info object provides information about the computer’s memory and operating system. The following list describes this object’s properties.

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Property	Purpose
AvailablePhysicalMemory	Returns the computer’s total amount of free physical memory in bytes.
AvailableVirtualMemory	Returns the computer’s total amount of free virtual address space in bytes.
InstalledUICulture	Returns the current user-interface culture.
LoadedAssemblies	Returns a collection of the assemblies loaded by the application.
OSFullName	Returns the computer’s full operating-system name as in Microsoft Windows XP Home Edition.
OSPlatform	Returns the platform identifier for the operating system of the computer. This can be Unix, Win32NT (Windows NT or later), Win32S (runs on 16-bit Windows to provide access to 32-bit applications), Win32Windows (Windows 95 or later), or WinCE.
OSVersion	Returns the operating system’s version in a string with the format major.minor.build.revision.
StackTrace	Returns a string containing the application’s current stack trace.
TotalPhysicalMemory	Returns the computer’s total amount of physical memory in bytes.
TotalVirtualMemory	Returns the computer’s total amount of virtual address space in bytes.
WorkingSet	Returns the amount of physical memory mapped to the process context in bytes.

Keyboard

This object returns information about the current keyboard state. The following table describes this object’s properties.

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Property	Purpose
AltKeyDown	Returns True if the Alt key is down.
CapsLock	Returns True if Caps Lock is on.
CtrlKeyDown	Returns True if the Ctrl key is down.
NumLock	Returns True if Num Lock is on.
ScrollLock	Returns True if Scroll Lock is on.
ShiftKeyDown	Returns True if the Shift key is down.

The My.Computer.Keyboard object also provides one method named SendKeys. This method sends keystrokes to the currently active window just as if the user had typed them. You can use this method to provide some automated control over applications.

Mouse

The My.Computer.Mouse object provides information about the computer’s mouse. The following table describes this object’s properties.

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Property	Description
ButtonsSwapped	Returns True if the functions of the mouse’s left and right buttons have been switched. This can make using the mouse easier for left-handed users.
WheelExists	Returns True if the mouse has a scroll wheel.
WheelScrollLines	Returns a number indicating how much to scroll when the mouse wheel rotates one notch.

Name

The My.Computer.Name property simply returns the computer’s name.

Network

The My.Computer.Network object provides a few simple properties and methods for working with the network. Its single property, IsAvailable, returns True if the network is available.

The following table describes the object’s methods.

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Method	Description
DownloadFile	Downloads a file from a remote computer. Parameters give such values as the file name, user name, password, and connection timeout.
IsAvailable	Returns True if the network is available.
Ping	Pings a remote computer to see if it is connected to the network.
UploadFile	Uploads a file to a remote computer. Parameters give such values as the file name, username, password, and connection timeout.

This object also provides one event, NetworkAvailabilityChanged, that you can catch to learn when the network becomes available or unavailable.

Ports

This object provides one property and a single method. Its SerialPortNames property returns an array of strings listing the names of the computer’s serial ports.

The OpenSerialPort method opens the serial port with a particular name (optional parameters give the baud rate, parity, data bits, and stop bits) and returns a reference to a SerialPort object.

The SerialPort class is much more complex than the My.Computer.Ports object. The following table describes the SerialPort class’s most useful properties.

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Property	Purpose
BaseStream	Returns the underlying Stream object.
BaudRate	Gets or sets the port’s baud rate.
BreakState	Gets or sets the break signal state.
BytesToRead	Returns the number of bytes of data in the receive buffer.
BytesToWrite	Returns the number of bytes of data in the send buffer.
CDHolding	Returns the state of the port’s Carrier Detect (CD) line.
CtsHolding	Returns the state of the port’s Clear-to-Send (CTS) line.
DataBits	Gets or sets the standard length of data bits per byte.
DiscardNull	Determines whether null characters are ignored.
DsrHolding	Returns the state of the Data Set Ready (DSR) signal.
DtrEnable	Determines enabling of the Data Terminal Ready (DTR) signal.
Encoding	Determines the character encoding for text conversion.
Handshake	Determines the handshaking protocol.
IsOpen	Returns True if the port is open.
NewLine	Determines the end-of-line sequence for the ReadLine and WriteLine methods. This is a linefeed by default.
Parity	Determines the parity-checking protocol.
ParityReplace	Determines the character used to replace invalid characters when a parity error occurs.
PortName	Gets or selects the port.
ReadBufferSize	Determines the port’s read buffer size.
ReadTimeout	Determines the read timeout in milliseconds.
ReceivedBytesThreshold	Determines the number of bytes in the input buffer before a ReceivedEvent is raised.
RtsEnable	Determines whether the Request to Transmit (RTS) signal is enabled.
StopBits	Determines the standard number of stop bits per byte.
WriteBufferSize	Determines the port’s write buffer size.
WriteTimeout	Determines the write timeout in milliseconds.

The following table describes the SerialPort object’s most useful methods.

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Method	Purpose
Close	Closes the port.
DiscardInBuffer	Discards any data that is currently in the read buffer.
DiscardOutBuffer	Discards any data that is currently in the write buffer.
GetPortNames	Returns an array of strings holding the serial ports’ names.
Open	Opens the port’s connection.
Read	Reads data from the read buffer.
ReadByte	Synchronously reads one byte from the read buffer.
ReadChar	Synchronously reads one character from the read buffer.
ReadExisting	Reads all immediately available characters in both the stream and the read buffer.
ReadLine	Reads up to the next NewLine value in the read buffer.
ReadTo	Reads a string up to the specified value in the read buffer.
Write	Writes data into the port’s write buffer.
WriteLine	Writes a string and a NewLine into the write buffer.

The SerialPort object also has a few events that you can use to learn about changes in the port’s status. The following table describes the object’s most useful events.

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Event	Purpose
DataReceived	Occurs when the port receives data. The e.EventType parameter indicates the type of data and can be SerialData .Eof (end of file received) or SerialData.Chars (characters were received).
ErrorEvent	Occurs when the port encounters an error. The e.EventType parameter indicates the type of error and can be Frame (framing error), Overrun (character buffer overrun), RxOver (input buffer overrun), RxParity (hardware detected parity error), or TxFull (output buffer full).
PinChangedEvent	Occurs when the port’s serial pin changes. The e.EventType parameter indicates the type of change and can be Break (break in the input), CDChanged (Receive Line Signal Detect, or RLSD, signal changed state), CtsChanged (CTS signal changed state), DsrChanged (DSR signal changed state), and Ring (detected a ring indicator).

Registry

My.Computer.Registry provides objects that manipulate the Registry. My.Computer.Registry has seven properties that refer to objects of type RegistryKey. The following table lists these objects and the corresponding Registry subtrees.

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My.Computer.Registry Property	Registry Subtree
ClassesRoot	HKEY_CLASSES_ROOT
CurrentConfig	HKEY_CURRENT_CONFIG
CurrentUser	HKEY_CURRENT_USER
DynData	HKEY_DYNAMIC_DATA
LocalMachine	HKEY_LOCAL_MACHINE
PerformanceData	HKEY_PERFORMANCE_DATA
Users	HKEY_USERS

My.Computer.Registry also provides two methods, GetValue and SetValue, that get and set Registry values.

The program can use the RegistryKey objects to work with the corresponding Registry subtrees. The following table describes the most useful properties and methods provided by the RegistryKey class.

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Property or Method	Purpose
Close	Closes the key and writes it to disk if it has been modified.
CreateSubKey	Creates a new subkey or opens an existing subkey within this key.
DeleteSubKey	Deletes the specified subkey.
DeleteSubKeyTree	Recursively deletes a subkey and any child subkeys it contains.
DeleteValue	Deletes a value from the key.
Flush	Writes any changes to the key into the Registry.
GetSubKeyNames	Returns an array of strings giving subkey names.
GetValue	Returns the value of a specified value within this key.
GetValueKind	Returns the type of a specified value within this key. This can be Binary, DWord, ExpandString, MultiString, QWord, String, or Unknown.
GetValueNames	Returns an array of strings giving the names of all of the values contained within the key.
Name	Returns the key’s Registry path.
OpenSubKey	Returns a RegistryKey object representing a descendant key. A parameter indicates whether you need write access to the key.
SetValue	Sets a value within the key.
SubKeyCount	Returns the number of subkeys that are this key’s direct children.
ToString	Returns the key’s name.
ValueCount	Returns the number of values stored in this key.

Visual Basic’s native Registry methods SaveSetting and GetSetting are generally easier to use than My.Computer.Registry, although they don’t provide access to the entire Registry.

Screen

The My.Computer.Screen property returns a Screen object representing the computer’s main display. The following table describes the Screen object’s most useful properties.

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Property	Purpose
AllScreens	Returns an array of Screen objects representing all of the system’s screens.
BitsPerPixel	Returns the screen’s color depth in bits per pixel.
Bounds	Returns a Rectangle giving the screen’s bounds in pixels.
DeviceName	Returns the screen’s device name as in “\\.\DISPLAY1.
Primary	Returns True if the screen is the computer’s primary screen.
PrimaryScreen	Returns a reference to a Screen object representing the system’s primary display. For a single display system, the primary display is the only display.
WorkingArea	Returns a Rectangle giving the screen’s working area bounds in pixels. This is the desktop area excluding taskbars, docked windows, and docked toolbars.

The following table describes the Screen class’s most useful methods.

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Method	Purpose
FromControl	Returns a Screen object representing the display that contains the largest piece of a specific control.
FromHandle	Returns a Screen object representing the display that contains the largest piece of the object with a given handle.
FromPoint	Returns a Screen object representing the display that contains a given point.
FromRectangle	Returns a Screen object representing the display that contains the largest piece of a given Rectangle.
GetBounds	Returns a Rectangle giving the bounds of the screen that contains the largest piece of a control, rectangle, or point.
GetWorkingArea	Returns a Rectangle giving the working area of the screen that contains the largest piece of a control, rectangle, or point.

The AllScreens and PrimaryScreen properties, and all of these methods, are shared members of the Windows.Forms.Screen class. If you refer to them using an instance of the class such as My.Computer.Screen, the IDE flags the code with a warning. You can avoid the warning by using the class itself (System.Windows.Forms.Screen) rather than an instance to refer to these properties, as in the following code:

  Debug.WriteLine(System.Windows.Forms.Screen.AllScreens(0).DeviceName) Debug.WriteLine(System.Windows.Forms.Screen.PrimaryScreen.DeviceName) 

The WorkingArea property does not update after you access the Screen object. If the user moves the system taskbar, the WorkingArea property does not show the new values.

The GetWorkingArea method retrieves the screen’s current working area, however. If you must be certain that the user has not moved the taskbar or a docked object, use the GetWorkingArea method.