Visual Basic .net

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

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

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

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.

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".

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