Develop Reference

Regular expression range that must not start at zero

I am trying to write a regular expression where only values from 1 thru 99 are allowed.
Valid values:
1
01
2
02
3
03
...
19
20
21
...
98
99
Everything else must throw an error like:
00
0
-1
1.0
1.
100
I currently have this:
^[1-9]([0-9]+$)
This is not working. It only accepts values from 10 and above.

This should do:
^(0[1-9]|[1-9][0-9]?)$

^(0?[1-9]|[1-9][0-9])$
first part covers 1 to 9 and the 0x
second part is for everything between 10 and 99

/^(0?[1-9]|[1-9][0-9])$/gm
Demo here.

Try this Regex:
^([1-9]|[1-9][0-9]|0[1-9])$/mg
Demo here Regex101
It uses the | operator which is equivalent to OR.
So basically this Regex is saying:
Is the number between 1 and 9?
OR
Is the first number between 1 and 9, and the second number between 0
and 9?
OR
Does the number begin with a 0 and end with a number between 1 and 9?
The flags on the end /mg just make it check each line for the demo, you may want to change or remove these.
Edit: For whatever reason I didn't see Kuba's answer. His is actually cleaner, but works in roughly the same way as this one should you have wanted an explanation.

This shoud work : ^(([0-9][1-9])|([1-9][0-9])|[1-9])$

Reading data over serial port from voltmeter

I'm sort of new at this and I'm writing a small application to read data from a voltmeter. It's a RadioShack Digital Multimeter 46-range. The purpose of my program is to perform something automatically when it detects a certain voltage. I'm using C# and I'm already familiar with the SerialPort class.
My program runs and reads the data in from the voltmeter. However, the data is all unformatted/gibberish. The device does come with its own software that displays the voltage on the PC, however this doesn't help me since I need to grab the voltage from my own program. I just can't figure out how to translate this data into something useful.
For reference, I'm using the SerialPort.Read() method:
byte[] voltage = new byte[100];
_serialPort.Read(voltage, 0, 99);
It grabs the data and displays it as so:
16 0 30 0 6 198 30 6 126 254 30 0 30 16 0 30 0 6 198 30 6 126 254 30 0 30 16 0 3
0 0 6 198 30 6 126 254 30 0 30 16 0 30 0 6 198 30 6 126 254 30 0 30 16 0 30 0 6
198 30 6 126 254 30 0 30 24 0 30 0 6 198 30 6 126 254 30 0 30 16 0 30 0 254 30 6
126 252 30 0 6 0 30 0 254 30 6 126 254 30 0
The space separates each element of the array. If I use a char[] array instead of byte[], I get complete gibberish:
▲ ? ? ▲ ♠ ~ ? ▲ ♠ ▲ ? ? ▲ ♠ ~ ? ▲ ♠ ▲ ? ? ▲ ♠ ~ ? ▲ ♠
Using the .ReadExisting() method gives me:
▲ ?~?♠~?▲ ▲? ▲ ?~♠~?▲ ?↑ ▲ ??~♠~?▲ F? ▲ ??~♠~?▲ D? ▲ ??~♠~?▲ f?
.ReadLine() times out, so doesn't work. ReadByte() and ReadChar() just give me numbers similar to the Read() into array function.
I'm in way over my head as I've never done something like this, not really sure where else to turn.

It sounds like you're close, but you need to figure out the correct Encoding to use.
To get a string from an array of bytes, you need to know the Code Page being used. If it's not covered in the manual, and you can't find it via a google/bing/other search, then you will need to use trial and error.
To see how to use GetChars() to get a string from a byte array, see Decoder.GetChars Method
In the code sample, look at this line:
Decoder uniDecoder = Encoding.Unicode.GetDecoder();
That line is specifically stating that you are to use the Unicode code page to get the correct code page.
From there, you can use an override of the Encoding class to specify different Code Pages. This is documented here: Encoding Class
If the Encoding being used isn't one of the standards, you can use the Encoding(Int32) override in the Constructor of the Encoding class. A list of valid Code Page IDs can be found at Code Pages Supported by Windows

There are two district strategies for solving your communications problem.
Locate and refer to appropriate documentation and design\modify a program to implement the specification.
The following may be appropriate, but are not guaranteed to describe the particular model DVM that you have. Nonetheless, they MAY serve as a starting point.
note that the authors of these documents comment that the Respective models may be 'visually identical', but also comments that '"Open-source packages that reportedly worked on LINUX with earlier RS-232 models do not work with the 2200039"
http://forums.parallax.com/attachment.php?attachmentid=88160&d=1325568007
http://sigrok.org/wiki/RadioShack_22-812
http://code.google.com/p/rs22812/
Try to reverse engineer the protocol. if you can read the data in a loop and collect the results, a good approach to reverse engineering a protocol, is to apply various representative signals to the DVM. You can use a short-circuit resistance measurements, various stable voltage measurements, etc.
The technique I suggest is most valuable is to use an automated variable signal generator. In this way, by analyzing the patterns of the data, you should be more readily be able to identify which points represent the raw data and which points represent stable descriptive data, like the unit of measurements, mode of operation, etc.

Some digital multimeters use 7 bit data transfer. You should set serial communication port to 7 data bits instead of standard 8 data bits.

I modified and merged a couple of older open source C programs together on linux in order to read the data values from the radio shack meter whose part number is 2200039. This is over usb. I really only added a C or an F on one range. My program is here, and it has the links where I got the other two programs in it.
I know this example is not in C#, but it does provide the format info you need. Think of it is as the API documentation written in C, you just have to translate it into C# yourself.
The protocol runs at 4800 baud, and 8N1 appears to work.

Read a file and get specific contents in an array

I'm very new to C# and I need your help.
I have a file named myData.txt with the following data in it.
Johnson 85 83 77 91 100
Aniston 80 90 95 93 48
Chen 78 81 11 90 73
Gupta 92 83 30 69 87
Blair 23 45 96 38 59
Lamah 100 100 100 100 100
The first three scores are 'Assignments' and the last two scores are 'Exams'.
All the names should go into a 1-dimensional array
Assignments into a 2-dim array
also Exams into a 2-dim array
My ultimate aim is to find out the average of assignments & exams for each student.

This is a homework assignment, so I'll just give you hints:
You can use StreamReader to open the file: StreamReader
Looks like each line ends with a new line. You can loop through the file and read each line via
StreamReader's ReadLine method: ReadLine
It looks like each line is delimited by tab. You can split the string returned by ReadLine on tab by using String's split method: Split. The char code for tab is '\t'. Splitting the string will put it into an array.
Convert the scores to a number, add, and then divide at the end to get the mean.

How do I detect frequency of mp3's in .NET?

I want to create a very simple piece of software in C# .NET that I can pass a folder's path to and detect all files with a frequency of below a given threshold. Any pointers on how I would do this?

You have to read mp3 files. To do that you have to find specifications for them.
Generally mp3 file is wrapped into ID3 tag, so that you have to read it, find its length and skip it. Let's take ID3v2.3 for example:
ID3v2/file identifier "ID3"
ID3v2 version $03 00
ID3v2 flags %abc00000
ID3v2 size 4 * %0xxxxxxx
so bytes 6,7,8,9 store header length in big-endian form. Here is sample of some file:
0 1 2 3 4 5 6 7 8 9 A B C D E F
49 44 33 03 00 00 00 00 07 76 54 43 4f 4e 00 00
07 76 - is the size. You need to shift left first byte so that actual size is 3F6. Then add 10 (A) to get the offset = 400. This is address of start of mp3 header.
Then you take description of mp3 header:
bits are: AAAAAAAA AAABBCCD EEEEFFGH IIJJKLMM, we need FF , sampling frequency and convert t to actual frequency:
bits MPEG1 MPEG2 MPEG2.5
00 44100 22050 11025
01 48000 24000 12000
10 32000 16000 8000
11 reserv. reserv. reserv.

You can use UltraID3Lib to get mp3 metadata (bitrate, frequency)

Check value of frequency bits in a file. There is some info about mp3 format.

Binary to Ascii and back again

I'm trying to interface with a hardware device via the serial port. When I use software like Portmon to see the messages they look like this:
42 21 21 21 21 41 45 21 26 21 29 21 26 59 5F 41 30 21 2B 21 27
42 21 21 21 21 41 47 21 27 21 28 21 27 59 5D 41 32 21 2A 21 28
When I run them thru a hex to ascii converter the commands don't make sense. Are these messages in fact something different than hex? My hope was to see the messages the device is passing and emulate them using c#. What can I do to find out exactly what the messages are?

Does the hardware device specify a protocol? Just because it's a serial port connection it doesn't mean that it has to be ASCII/Readable english Text. It could as well be just a sequence of bytes where for example 42 is a command and 21212121 is data to that command. Could be an initialization sequence or whatever.
At the end of the day, all you work with is a series of bytes. The meaning of them can be found in a protocol specification or if you don't have one, you need to manually look at each command. Issue a command to the device, capture the input, issue another command.
Look for patterns. Common Initialization? What could be the commands? What data gets passed?
Yes, it's tedious, but reverse engineering is rarely easy.
The ASCII for the Hex is this:
B!!!!AE!&!)!&Y_A0!+!'
B!!!!AG!'!(!'Y]A2!*!(
That does look like some sort of protocol to me, with some Initialization Sequence (B!!!!) and commands (AE and AG), but that's just guessing.

The decive is sending data to the computer. All digital data has the form of ones and zeroes, such as 10101001010110010... . Most often one combines groups of eight such bits (binary digits) into bytes, so all data consists of bytes. One byte can thus represent any of the 2^8 values 0 to 2^8 - 1 = 255, or, in hexadecimal notation, any of the numbers 0x00 to 0xFF.
Sometimes the bytes represent a string of alphanumerical (and other) characters, often ASCII encoded. This data format assigns a character to each value from 0 to 127. But all data is not ASCII-encoded characters.
For instance, if the device is a light-intensity sensor, then each byte could give the light intensity as a number between 0 (pitch-black) and 255 (as bright as it gets). Or, the data could be a bitmap image. Then the data would start with a couple of well-defined structures (namely this and this) specifying the colour depth (number of bits per pixel, i.e. more or less the number of colours), the width, the height, and the compression of the bitmap. Then the pixel data would begin. Typically the bytes would go BBGGRRBBGGRRBBGGRR where the first BB is the blue intensity of the first pixel, the first GG is the green intensity of the first pixel, the first RR is the red intensity of the first pixel, the second BB is the blue intensity of the second pixel, and so on.
In fact the data could mean anything. Whay kind of device is it? Does it have an open specification?