Difference between revisions of "Visual Basic .net"
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<code>InStr("this is a string", "is")</code><br /> | <code>InStr("this is a string", "is")</code><br /> | ||
returns (character position number) 6. This function returns 0 when not found. | returns (character position number) 6. This function returns 0 when not found. | ||
+ | |||
+ | '''using the middle of a string:'''<br /> | ||
+ | <code> | ||
+ | dim str as string<br /> | ||
+ | dim outputstr as string<br /> | ||
+ | str="this is a string"<br /> | ||
+ | outputstr=str.Substring(0, 4)<br /> | ||
+ | </code> | ||
+ | Starts at character 0 (the first character) and reads 4 characters (including the first one). |
Revision as of 09:11, 27 December 2009
Contents
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)
- 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)
Arrays
Threading / Parallel
Loops
Conditionals
Math
RS-232
Datatypes
VB type | .net type | Size | Range |
---|---|---|---|
Boolean
|
System.Boolean
|
4 bytes | True or False |
Byte
|
System.Byte
|
1 byte | 0 to 255 (unsigned) |
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 |
Long
|
System.Int64
|
8 bytes | -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 |
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 |
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 |
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 middle of a string:
dim str as string
Starts at character 0 (the first character) and reads 4 characters (including the first one).
dim outputstr as string
str="this is a string"
outputstr=str.Substring(0, 4)