Difference between revisions of "Visual Basic .net"

Revision as of 11:51, 27 December 2009

1 Graphics
- 1.1 setting up graphics and drawing pixels, shapes, and colours
- 1.2 Copies bitmap named bm into a 1D array called picArray as A,R,G,B,A,R,G,B,...
2 Files
3 Arrays
4 Threading / Parallel
- 4.1 Distribute tasks automatically on all available cores
5 Loops
6 Conditionals
7 Math
8 Calling Windows API
9 RS-232
- 9.1 sending an entire array of bytes
- 9.2 Reading a byte
10 Network / Internet
- 10.1 POST text to a PHP program on a WEB server
- 10.2 Downloading HTML as a string from a web page
11 Strings
12 Datatypes

Graphics

setting up graphics and drawing pixels, shapes, and colours


Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
Dim gr As Graphics = Graphics.FromImage(bm)
bm.SetPixel(10, 10, Color.FromArgb(255, 255, 0, 0))
Dim greenthickpen As New Pen(Color.FromArgb(255, 0, 255, 0), 10)
gr.DrawLine(greenthickpen, 20, 20, 40, 40)
gr.DrawArc(Pens.Blue, 80, 80, 20, 20, 0, 360)
gr.FillPie(Brushes.Black, 150, 150, 20, 20, 0, 360)
Dim rect As Rectangle
rect.Width = 10
rect.Height = 10
rect.X = 200
rect.Y = 200
gr.DrawRectangle(Pens.Black, rect)
Dim triangle(2) As Point
triangle(0).X = 5
triangle(0).Y = 0 + 30
triangle(1).X = 0
triangle(1).Y = 5 + 30
triangle(2).X = 10
triangle(2).Y = 5 + 30
gr.FillPolygon(Brushes.Blue, triangle)
PictureBox1.Image = bm

Color.FromArgb(255, 255, 0, 0) is in the format of Alpha, Red, Green, Blue

Copies bitmap named bm into a 1D array called picArray as A,R,G,B,A,R,G,B,...


Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
Dim pict2 As New Bitmap(PictureBox1.Width, PictureBox1.Height)
Dim gr As Graphics = Graphics.FromImage(bm)
Dim bmdR As System.Drawing.Imaging.BitmapData
Dim picArray() As Byte
Select Case bm.PixelFormat
	Case Imaging.PixelFormat.Format24bppRgb, Imaging.PixelFormat.Format32bppArgb, Imaging.PixelFormat.Format32bppPArgb, Imaging.PixelFormat.Format32bppRgb
	'Nothing to do here, this is our native format
	Case Else
	'Convert all other formats to our native format of RGB 8 bit per primary colour
	Pict2 = New Bitmap(bm.Width, bm.Height, Imaging.PixelFormat.Format32bppArgb)
	gr = Graphics.FromImage(Pict2)
		gr.DrawImageUnscaled(bm, 0, 0)
		bm = Pict2
	End Select
bmdR = bm.LockBits(New Rectangle(0, 0, bm.Width, bm.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, bm.PixelFormat)
frameSize = bmdR.Stride * bmdR.Height
ReDim picArray(frameSize)
System.Runtime.InteropServices.Marshal.Copy(bmdR.Scan0, picArray, 0, frameSize)
bm.UnlockBits(bmdR)

Files

Reading text files line by line


Dim f1 As Long
dim filestring as string
f1 = FreeFile()
FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Input)
Do Until EOF(f1)
	filestring=LineInput(f1)
Loop
FileClose(f1)

Note My.Application.Info.DirectoryPath & "\filename.txt" may be replaced by "C \some_path\file.txt"

Writing text files line by line


Dim f1 As Long
f1 = FreeFile()
FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Output
Print(f1, "This is line 1")
Print(f1, "This is line 2")
FileClose(f1)

loading data files into an array of bytes


Dim oFile As System.IO.FileInfo
oFile = New System.IO.FileInfo(My.Application.Info.DirectoryPath & "\file.dat")
Dim oFileStream As System.IO.FileStream = oFile.OpenRead()
Dim lBytes As Long = oFileStream.Length
If (lBytes > 0) Then
	ReDim fileData(lBytes - 1)
	oFileStream.Read(fileData, 0, lBytes)
	oFileStream.Close()
End If

Using a "Browse" button


Dim ofd As New OpenFileDialog
dim f1 as Long
If ofd.ShowDialog() = Windows.Forms.DialogResult.OK Then
	f1 = FreeFile()
	Try
		FileOpen(f1, ofd.FileName, OpenMode.Input)
	Catch ex As Exception
		MsgBox(ex.Message)
		err = 1
	End Try

	If err = 0 Then
		'read the file here
	End If
End if

Arrays

Threading / Parallel

Distribute tasks automatically on all available cores

Imports System.Threading
Imports System.Threading.Tasks

Parallel.For(0, yRes - 1, Function(n) mandelbrotline(n, cr + xr, ci + yr, mandN, xRes, xStp, yStp, picarray))

n will iterate from 0 to yres -1 in no particular order
Requires .net 4 or Parallel extensions on .net 3.5

Loops

Conditionals

Math

Rounding


Math.Round(3.14159,2)

Rounds to 2 decimal places, giving 3.14

Seperating just the whole part of a number


Int(3.14159,2)

Gives 3

Seperating just the fractional part of a number


double pi
double frac
pi=3.14159
frac=pi-Int(pi)

Gives 0.14159

Calling Windows API


Public Declare Function QueryPerformanceCounter Lib "kernel32.dll" (ByRef Counter As Long) As Integer
Public Declare Function QueryPerformanceFrequency Lib "kernel32.dll" (ByRef counter As Long) As Integer

Dim curFreq, tStart, tStop As UInt64
QueryPerformanceFrequency(curFreq)
QueryPerformanceCounter(tStart)
...your code
QueryPerformanceCounter(tStop)
msgbox(CStr(CInt(1 / ((tStop - tStart) / curFreq))) & " Frames per second")

RS-232

sending an entire array of bytes


SerialPort1.Write(bytearray, 0, arraylength)

0 indicated the index to start reading the array, arraylength is a variable containing the number of bytes to transmit.
This operation is incredibly fast compared to looping through the array and sending 1 byte at a time. This is especially useful for high speed serial ports.

Reading a byte


Dim serialbyte as Byte
serialbyte=SerialPort1.ReadByte

Network / Internet

POST text to a PHP program on a WEB server

Imports System.Net
Dim client As WebClient = New WebClient()
Dim encoding As New System.Text.ASCIIEncoding()
client.Headers.Add("Content-Type", "application/x-www-form-urlencoded")
client.UploadData(URL & "net2.php", "POST", encoding.GetBytes("data=" & text))
client.Dispose()

Downloading HTML as a string from a web page


Dim webClient As System.Net.WebClient = New System.Net.WebClient()
Dim result As String

Try
	result = webClient.DownloadString("http://www.google.com")
Catch ex As Exception
	MsgBox(ex.Message)
End Try
If result <> "" Then
	MsgBox(result)
End If

Strings

Finding text in a string


InStr("this is a string", "is")

returns (character position number) 6. This function returns 0 when not found.

Using the start of a string


dim str as string
dim outputstr as string
str="this is a string"
outputstr=str.Substring(0, 4)

Starts at character index 0 (the first character), and reads 4 characters (including the first one), resulting in "this".

Using the middle of a string


dim str as string
dim outputstr as string
str="this is a string"
outputstr=str.Substring(5, 4)

Starts at character index 5 (the 6th character), and reads 4 characters, resulting in "is a".

Using the end of a string


dim str as string
dim outputstr as string
str="this is a string"
outputstr=str1.Substring(str1.Length - 4, 4)

Starts 4 chacters before the end, and reads 4 characters, resulting in "ring".

Getting just the path of a file given the entire path and filename as a string


PathStr.Substring(0, ofd.FileName.LastIndexOf("\")) & "\"

Getting just the file name (with extension) of a file given the entire path and filename as a string


System.IO.Path.GetFileName(PathStr)

Getting just the file name (without extension) of a file given the entire path and filename as a string


System.IO.Path.GetFileNameWithoutExtension(PathStr)

Datatypes

VB type	.net type	Size	Range
`Boolean`	`System.Boolean`	4 bytes	True or False
`Byte`	`System.Byte`	1 byte	0 to 255 (unsigned)
`SByte`	`System.SByte`	1 byte	-128 through 127 (signed)
`Char`	`System.Char`	2 bytes	0 to 65535 (unsigned)
`Date`	`System.DateTime`	8 bytes	January 1, 1 CE to December 31, 9999
`Decimal`	`System.Decimal`	12 bytes	+/-79,228,162,514,264,337,593,543,950,335 with no decimal point; +/-7.9228162514264337593543950335 with 28 places to the right of the decimal; smallest non-zero number is +/-0.0000000000000000000000000001
`Double`	`System.Double`	8 bytes	-1.79769313486231E308 to -4.94065645841247E-324 for negative values; 4.94065645841247E-324 to 1.79769313486232E308 for positive values
`Integer`	`System.Int32`	4 bytes	-2,147,483,648 to 2,147,483,647
`UInteger`	`System.UInt32`	4 bytes	0 through 4,294,967,295 (unsigned)
`Long`	`System.Int64`	8 bytes	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
`ULong`	`System.UInt64`	8 bytes	0 through 18,446,744,073,709,551,615 (1.8...E+19) (unsigned)
`Object`	`System.Object` (class)	4 bytes	Any type can be stored in a variable of type `Object`
`Short`	`System.Int16`	2 bytes	-32,768 to 32,767
`UShort`	`System.UInt16`	2 bytes	0 through 65,535 (unsigned)
`Single`	`System.Single`	4 bytes	-3.402823E38 to -1.401298E-45 for negative values; 1.401298E-45 to 3.402823E38 for positive values
`String`	`System.String` (class)	10 bytes + (2 * string length)	0 to approximately two billion Unicode characters
User-Defined Type (structure)	(inherits from `System.ValueType`)	Sum of the sizes of its members	Each member of the structure has a range determined by its data type and independent of the ranges of the other members

@@ Line 135: / Line 135: @@
 </code>
 Rounds to 2 decimal places, giving 3.14
+===Seperating just the whole part of a number===
+<code>
+ Int(3.14159,2)
+</code>
+Gives 3
+===Seperating just the fractional part of a number===
+<code>
+ double pi
+ double frac
+ pi=3.14159
+ frac=pi-Int(pi)
+</code>
+Gives 0.14159
 ==Calling Windows API==