Difference between revisions of "Visual Basic .net"

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Line 4: Line 4:
 
  Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
 
  Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
 
  Dim gr As Graphics = Graphics.FromImage(bm)
 
  Dim gr As Graphics = Graphics.FromImage(bm)
−
  bm.SetPixel(10, 10, Color.FromArgb(255, 255, 0, 0))<br />
+
  bm.SetPixel(10, 10, Color.FromArgb(255, 255, 0, 0))
−
  Dim greenthickpen As New Pen(Color.FromArgb(255, 0, 255, 0), 10)<br />
+
  Dim greenthickpen As New Pen(Color.FromArgb(255, 0, 255, 0), 10)
−
  gr.DrawLine(greenthickpen, 20, 20, 40, 40)<br />
+
  gr.DrawLine(greenthickpen, 20, 20, 40, 40)
−
  gr.DrawArc(Pens.Blue, 80, 80, 20, 20, 0, 360)<br />
+
  gr.DrawArc(Pens.Blue, 80, 80, 20, 20, 0, 360)
−
  gr.FillPie(Brushes.Black, 150, 150, 20, 20, 0, 360)<br />
+
  gr.FillPie(Brushes.Black, 150, 150, 20, 20, 0, 360)
−
  Dim rect As Rectangle<br />
+
  Dim rect As Rectangle
−
  rect.Width = 10<br />
+
  rect.Width = 10
−
  rect.Height = 10<br />
+
  rect.Height = 10
−
  rect.X = 200<br />
+
  rect.X = 200
−
  rect.Y = 200<br />
+
  rect.Y = 200
−
  gr.DrawRectangle(Pens.Black, rect)<br />
+
  gr.DrawRectangle(Pens.Black, rect)
−
  Dim triangle(2) As Point<br />
+
  Dim triangle(2) As Point
−
  triangle(0).X = 5<br />
+
  triangle(0).X = 5
−
  triangle(0).Y = 0 + 30<br />
+
  triangle(0).Y = 0 + 30
−
  triangle(1).X = 0<br />
+
  triangle(1).X = 0
−
  triangle(1).Y = 5 + 30<br />
+
  triangle(1).Y = 5 + 30
−
  triangle(2).X = 10<br />
+
  triangle(2).X = 10
−
  triangle(2).Y = 5 + 30<br />
+
  triangle(2).Y = 5 + 30
−
  gr.FillPolygon(Brushes.Blue, triangle)<br />
+
  gr.FillPolygon(Brushes.Blue, triangle)
−
  PictureBox1.Image = bm<br />
+
  PictureBox1.Image = bm
 
</code>
 
</code>
−
Color.FromArgb(255, 255, 0, 0) is in the format of Alpha, Red, Green, Blue  
+
<br />
 +
Color.FromArgb(255, 255, 0, 0) is in the format of Alpha, Red, Green, Blue<br />
  
  
Line 32: Line 33:
 
'''Reading text files line by line:'''<br />
 
'''Reading text files line by line:'''<br />
 
<code>
 
<code>
−
  Dim f1 As Long<br />
+
  Dim f1 As Long
 
  dim filestring as string
 
  dim filestring as string
−
  f1 = FreeFile()<br />
+
  f1 = FreeFile()
−
  FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Input)<br />
+
  FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Input)
−
  Do Until EOF(f1)<br />
+
  Do Until EOF(f1)
−
  :filestring=LineInput(f1)<br />
+
  :filestring=LineInput(f1)
−
  Loop<br />
+
  Loop
−
  FileClose(f1)<br />
+
  FileClose(f1)
 
</code>
 
</code>
−
Note: My.Application.Info.DirectoryPath & "\filename.txt" may be replaced by "C:\some_path\file.txt"
+
<br />
 +
Note: My.Application.Info.DirectoryPath & "\filename.txt" may be replaced by "C:\some_path\file.txt"<br />
  
  
 
'''Writing text files line by line:'''<br />
 
'''Writing text files line by line:'''<br />
 
<code>
 
<code>
−
  Dim f1 As Long<br />
+
  Dim f1 As Long
−
  f1 = FreeFile()<br />
+
  f1 = FreeFile()
−
  FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Output<br />
+
  FileOpen(f1, My.Application.Info.DirectoryPath & "\filename.txt", OpenMode.Output
−
  Print(f1, "This is line 1")<br />
+
  Print(f1, "This is line 1")
−
  Print(f1, "This is line 2")<br />
+
  Print(f1, "This is line 2")
−
  FileClose(f1)<br />
+
  FileClose(f1)
 
</code>
 
</code>
 +
<br />
  
  
 
'''loading data files into an array of bytes'''<br />
 
'''loading data files into an array of bytes'''<br />
 
<code>
 
<code>
−
  Dim oFile As System.IO.FileInfo<br />
+
  Dim oFile As System.IO.FileInfo
−
  oFile = New System.IO.FileInfo(My.Application.Info.DirectoryPath & "\file.dat")<br />
+
  oFile = New System.IO.FileInfo(My.Application.Info.DirectoryPath & "\file.dat")
−
  Dim oFileStream As System.IO.FileStream = oFile.OpenRead()<br />
+
  Dim oFileStream As System.IO.FileStream = oFile.OpenRead()
−
  Dim lBytes As Long = oFileStream.Length<br />
+
  Dim lBytes As Long = oFileStream.Length
−
  If (lBytes > 0) Then<br />
+
  If (lBytes > 0) Then
−
  ReDim fileData(lBytes - 1)<br />
+
  :ReDim fileData(lBytes - 1)
−
  :oFileStream.Read(fileData, 0, lBytes)<br />
+
  :oFileStream.Read(fileData, 0, lBytes)
−
  :oFileStream.Close()<br />
+
  :oFileStream.Close()
−
  End If<br />
+
  End If
 
</code>
 
</code>
 +
<br />
  
 
==Arrays==
 
==Arrays==
  
 
==Threading / Parallel==
 
==Threading / Parallel==
−
'''Distribute tasks automatically on all available cores'''<br>
+
'''Distribute tasks automatically on all available cores'''<br />
 
<code>
 
<code>
−
  Imports System.Threading<br>
+
  Imports System.Threading
−
  Imports System.Threading.Tasks<br>
+
  Imports System.Threading.Tasks
  
−
Parallel.For(0, yRes - 1, Function(n) mandelbrotline(n, cr + xr, ci + yr, mandN, xRes, xStp, yStp, picarray))<br>
+
Parallel.For(0, yRes - 1, Function(n) mandelbrotline(n, cr + xr, ci + yr, mandN, xRes, xStp, yStp, picarray))
 
</code>
 
</code>
−
n will iterate from 0 to yres -1 in no particular order<br>
+
<br />
−
Requires .net 4 or Parallel extensions on .net 3.5
+
n will iterate from 0 to yres -1 in no particular order<br />
 +
Requires .net 4 or Parallel extensions on .net 3.5<br />
  
 
==Loops==
 
==Loops==
Line 88: Line 93:
 
==Calling Windows API==
 
==Calling Windows API==
 
<code>
 
<code>
−
  Public Declare Function QueryPerformanceCounter Lib "kernel32.dll" (ByRef Counter As Long) As Integer<br>
+
  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<br>
+
  Public Declare Function QueryPerformanceFrequency Lib "kernel32.dll" (ByRef counter As Long) As Integer
  
−
  Dim curFreq, tStart, tStop As UInt64<br>
+
  Dim curFreq, tStart, tStop As UInt64
−
  QueryPerformanceFrequency(curFreq)<br>
+
  QueryPerformanceFrequency(curFreq)
−
  QueryPerformanceCounter(tStart)<br>
+
  QueryPerformanceCounter(tStart)
−
  ...your code<br>
+
  ...your code
−
  QueryPerformanceCounter(tStop)<br>
+
  QueryPerformanceCounter(tStop)
−
  msgbox(CStr(CInt(1 / ((tStop - tStart) / curFreq))) & " Frames per second")<br>
+
  msgbox(CStr(CInt(1 / ((tStop - tStart) / curFreq))) & " Frames per second")
 
</code>
 
</code>
 +
<br />
  
 
==RS-232==
 
==RS-232==
 
'''sending an entire array of bytes'''<br />
 
'''sending an entire array of bytes'''<br />
 
<code>
 
<code>
−
  SerialPort1.Write(bytearray, 0, arraylength)<br />
+
  SerialPort1.Write(bytearray, 0, arraylength)
 
</code>
 
</code>
 +
<br />
 
0 indicated the index to start reading the array, arraylength is a variable containing the number of bytes to transmit.<br />
 
0 indicated the index to start reading the array, arraylength is a variable containing the number of bytes to transmit.<br />
−
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.  
+
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. <br />
  
 
==Strings==
 
==Strings==
 
'''Finding text in a string:'''<br />
 
'''Finding text in a string:'''<br />
 
<code>
 
<code>
−
  InStr("this is a string", "is")<br />
+
  InStr("this is a string", "is")
 
</code>
 
</code>
−
returns (character position number) 6. This function returns 0 when not found.
+
<br />
 +
returns (character position number) 6. This function returns 0 when not found.<br />
  
  
 
'''Using the start of a string:'''<br />
 
'''Using the start of a string:'''<br />
 
<code>
 
<code>
−
  dim str as string<br />
+
  dim str as string
−
  dim outputstr as string<br />
+
  dim outputstr as string
−
  str="this is a string"<br />
+
  str="this is a string"
−
  outputstr=str.Substring(0, 4)<br />
+
  outputstr=str.Substring(0, 4)
 
</code>
 
</code>
−
Starts at character index 0 (the first character), and reads 4 characters (including the first one), resulting in "this".
+
<br />
 +
Starts at character index 0 (the first character), and reads 4 characters (including the first one), resulting in "this".<br />
  
  
 
'''Using the middle of a string:'''<br />
 
'''Using the middle of a string:'''<br />
 
<code>
 
<code>
−
  dim str as string<br />
+
  dim str as string
−
  dim outputstr as string<br />
+
  dim outputstr as string
−
  str="this is a string"<br />
+
  str="this is a string"
−
  outputstr=str.Substring(5, 4)<br />
+
  outputstr=str.Substring(5, 4)
 
</code>
 
</code>
−
Starts at character index 5 (the 6th character), and reads 4 characters, resulting in "is a".
+
<br />
 +
Starts at character index 5 (the 6th character), and reads 4 characters, resulting in "is a".<br />
  
  
 
'''Using the end of a string:'''<br />
 
'''Using the end of a string:'''<br />
 
<code>
 
<code>
−
  dim str as string<br />
+
  dim str as string
−
  dim outputstr as string<br />
+
  dim outputstr as string
−
  str="this is a string"<br />
+
  str="this is a string"
−
  outputstr=str1.Substring(str1.Length - 4, 4)<br />
+
  outputstr=str1.Substring(str1.Length - 4, 4)
 
</code>
 
</code>
−
Starts 4 chacters before the end, and reads 4 characters, resulting in "ring".
+
<br />
 +
Starts 4 chacters before the end, and reads 4 characters, resulting in "ring".<br />
  
 
==Datatypes==
 
==Datatypes==

Revision as of 10:09, 27 December 2009

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


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

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
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