Difference between revisions of "Visual Basic .net"

Revision as of 09:29, 27 December 2009

Graphics

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)


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)


End If


Arrays

Threading / Parallel

Loops

Conditionals

Math

RS-232

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