Re: ReadAllBytes Method of the File Class PROBLEM - C# Discussion Boards

10-Feb-14 4:39

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Applica
{
    class Program
    {
        static void Main(string[] args)
        {
            long Totbyte = 0;//file length initialize to 0
            DirectoryInfo da = new DirectoryInfo("C:\\Folder");//local file on the computer
            FileInfo[] Arr = da.GetFiles();
            foreach (FileInfo ap in Arr)
                Totbyte = ap.Length;//real file length on local computer
            Console.WriteLine("Total Bytes = {0} bytes", Totbyte);//the code works great up to this point
            
            //want to set up an array for the exact file length above and read all bytes into the array
            //not sure of what I am doing below, but its not working out
            string temPath = Path.GetTempFileName();
            string temPath2 = Path.GetTempFileName();
                if (File.Exists(temPath))
                {
                    byte[Totbyte] data = File.ReadAllBytes(temPath);
                    File.WriteAllBytes(temPath2, data);
                }
        }
    }
}

Richard Deeming10-Feb-14 5:30

Richard Deeming

10-Feb-14 5:30

computerpublic wrote:
//the code works great up to this point

Well, it runs, but it might not be doing what you think it's doing. You're displaying the length of the last file in the directory, but your loop and variable name suggest you want to display the total length of all files in the directory. That's quite a simple change:

foreach (FileInfo ap in Arr)
    Totbyte += ap.Length;

Note the "+=" instead of just "=".

computerpublic wrote:
//want to set up an array for the exact file length above and read all bytes into the array

Firstly, what would the length of the files in C:\Folder have to do with the length of a temporary file?

Secondly, the ReadAllBytes method will return an array of the correct size to contain all of the bytes in the file you're reading. You don't need to specify the size of the array.

byte[] data = File.ReadAllBytes(tempPath);

Thirdly, since you're just copying one file to another, why not simple use the File.Copy method?

if (File.Exists(temPath))
{
    File.Copy(temPath, temPath2, true);
}

Finally, look at the documentation of GetTempFileName:

http://msdn.microsoft.com/en-us/library/system.io.path.gettempfilename%28v=vs.110%29.aspx[^]
Creates a uniquely named, zero-byte temporary file on disk and returns the full path of that file.

That means that temPath will always exist, and will be an empty file. Copying it over another empty file will have no effect.

Perhaps if you explain what you're trying to do, we might be able to point you in the right direction. Smile | :)

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

computerpublic10-Feb-14 5:45

10-Feb-14 5:45

I already have the file on my computer.  I do not want to read the file to my computer.  I want to read the file into an array. I did not know that the array would automatically be the right size. I do not know which of the identifiers is the array. How do I go about accessing the array.

Richard Deeming10-Feb-14 5:56

Richard Deeming

10-Feb-14 5:56

It's still not clear what you're trying to achieve.

If you want to read the content of a binary file:

// Read the content of the specified file into an array called "data":
byte[] data = File.ReadAllBytes("C:\Folder\TheFileToRead.ext");

for (int index = 0; index < data.Length; index++)
{
    // Access the array:
    byte theByteAtThisIndex = data[index];
    
    ...
}

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

computerpublic10-Feb-14 6:27

10-Feb-14 6:27

Your explanation is great. I know I am using a byte array (I don't think a bit array exist), but how do i go about accessing the bits of each byte in the array?

Richard Deeming10-Feb-14 6:54

Richard Deeming

10-Feb-14 6:54

You would use bitwise operators to extract the individual bits from each byte:
Understand how bitwise operators work (C# and VB.NET examples)[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Matt T Heffron10-Feb-14 7:47

Matt T Heffron

10-Feb-14 7:47

You can use the BitArray class to treat the array of bytes as an array of bits.

byte[] data = File.ReadAllBytes("C:\Folder\TheFileToRead.ext");
BitArray dataAsBits = new BitArray(data);

See BitArray Class[^]
Note the order of the bits in the bytes!!

BillWoodruff10-Feb-14 21:23

BillWoodruff

10-Feb-14 21:23

Upvoted ! At the time I wrote my response to this thread, Richard's reply was not available here, which is becoming all too typical: there is often a gap of hours before content on QA and Forums shows up, and, yet, other parts of CodeProject seem to be updated instantly.

Had I seen Richard's response, I would not have posted.

“But I don't want to go among mad people,” Alice remarked.

“Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.”

“How do you know I'm mad?” said Alice.

“You must be," said the Cat, or you wouldn't have come here.” Lewis Carroll

BillWoodruff10-Feb-14 6:37

BillWoodruff

10-Feb-14 6:37

I can't understand what you are trying to do here:

1. you get a Directory, and then you iterate over all its files setting a variable to the current file length: which means the value of 'Totbyte is always going to be equal to the length of the last file read.

Did you mean to make a total of the length of all files ? in which case you should have: Totbyte += ap.Length; ?

2. then you create two temporary files, and check if one of them exists, and read its bytes into a byte[], which makes no sense, since the temp file will have no content.

Isn't it the case that the file (files ?) you want to read have something to do with the first part of your code, where you create an array of files from a Directory path ?

computerpublic10-Feb-14 6:51

10-Feb-14 6:51

Ideally what I am trying to do is copy of a file off my desktop in an Array of Bits (not Bytes).  Can you please explain how this can be done?

Dave Kreskowiak10-Feb-14 7:14

Dave Kreskowiak

10-Feb-14 7:14

Richard Deeming already gave you the answer to this.

You could use the BitArray class[^] to give you access to the bits in each byte, but it's not exactly what I would call "efficient".

You would still have to read the file into a byte array and then pass the byte array to the BitArray constructor.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Lock Controls or Record for Add/Edit/Delete C#

Matt T Heffron10-Feb-14 7:49

Matt T Heffron

10-Feb-14 7:49

I really should have read all of the comments before posting my (redundant) suggestion of BitArray.... D'Oh! | :doh:

ahmed_one9-Feb-14 22:59

ahmed_one

9-Feb-14 22:59

Dear All,

I am using Visual Studio 2010 ultimate, C# language and MySql as backend database.

I've a Voucher Form, which is Master Detail. After user enters voucher data, he save the data in database by clicking save button. Now I need to add a post button, which when click perform a update to Voucher record and mark it as POSTED. This is not an issue as it simply required an Sql update statement.

What I need is a way, that after POSTED is marked, no one can edit the record, even when it is search by any user. What is the best way to do it? Are programmers do it by setting readonly property of controls true/false? Or there are other options available?

Any ideas/suggestions/samples much appreciated.

Best regards

Ahmed

Keith Barrow10-Feb-14 1:04

Keith Barrow

10-Feb-14 1:04

ahmed_one wrote:
What I need is a way, that after POSTED is marked, no one can edit the record, even when it is search by any user.

Can this be clarified a little please? There are a few different potential problems here. First off, what do you mean by "no one can edit the record"? The database admin is going to be able to edit the record, one way or another. If you mean users should not be able to edit the record, then you are in control of what they do in the application, so you must have enabled the ability to updated? I don't know why searching alters the record (as your comment seems to suggest) - this sounds like something is very wonky to me, or you don't mean database record. It might be better to expand on your question.

ahmed_one wrote:
Are programmers do it by setting readonly property of controls true/false? Or there are other options available?

Yes, it is possible and normal to do this (normally a check-box). The other options depend on what you need so no-one can answer that for you, you might want to consult the people you are writing the software for.

PB 369,783 wrote:
I just find him very unlikeable, and I think the way he looks like a prettier version of his Mum is very disturbing.[^]

ahmed_one10-Feb-14 1:13

ahmed_one

10-Feb-14 1:13

Keith Barrow wrote:
ahmed_one wrote:
What I need is a way, that after POSTED is marked, no one can edit the record, even when it is search by any user.

Can this be clarified a little please? There are a few different potential problems here. First off, what do you mean by "no one can edit the record"? The database admin is going to be able to edit the record, one way or another. If you mean users should not be able to edit the record, then you are in control of what they do in the application, so you must have enabled the ability to updated? I don't know why searching alters the record (as your comment seems to suggest) - this sounds like something is very wonky to me, or you don't mean database record. It might be better to expand on your question.

By "No one can edit the record" I mean users. Database admin surely can alter the data. That's not a problem. At present, searching is not altering the record, my requirement is: when POSTED is marked users are restricted to Add/Edit/Delete/Update that POSTED record. This means when user use find function to display record (which is POSTED now) in Winforms, it should be locked for ADD/EDIT/DELETE/UPDATE.

Keith Barrow10-Feb-14 1:54

Keith Barrow

10-Feb-14 1:54

It's been a long time since I've done any winforms, but in principal I'd:

Extract the UI that allows viewing/adding/updating the record as a control.
Set the control from above's enabled state to false - this will disable the control
Show/hide buttons in the control as appropriate

PB 369,783 wrote:
I just find him very unlikeable, and I think the way he looks like a prettier version of his Mum is very disturbing.[^]

ahmed_one10-Feb-14 2:36

ahmed_one

10-Feb-14 2:36

Thanks for your reply,

Are there any option available via Sql, when user find the record, the find function should call a function which fetch data from MySql Db in read-only mode.