whats wrong with this code...?

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i have a code to read a file ... but it shows some error ....
so what can i do....

C#

using System;
using System.IO;
class FileRead
{
    string filereadbuf;  
    public void ReadFile(string FileName, int FileSize)
    {
        char[] buf = new char[FileSize];  
        
        StreamReader sr = new StreamReader(new FileStream(FileName, FileMode.Open, FileAccess.Read));
        int retval = sr.ReadBlock(buf, 0, FileSize); // 
        Console.Write("Total Bytes Read = " + retval + "\n");
        filereadbuf = new string(buf);  
        Console.WriteLine(filereadbuf); 
        sr.Close();
    }
}
 
class TestFileRead
{
    public static void Main(string[] args)
    {
        String[] cmdline = Environment.GetCommandLineArgs(); 
        Console.WriteLine("File Reader Using Stream Reader & File Stream \n");
        if (cmdline.Length < 2) 
        {
            Console.WriteLine("Usage: " + cmdline[0] + " <input file> ");
            return;
        }
      
      
        File[] fe = (new Directory(".")).GetFiles(cmdline[1]);
        if (fe.Length == 0)
        {
            Console.WriteLine(cmdline[1] + ": file not found"); 
            return;
        }
        FileRead fr = new FileRead();
        try
        {
            fr.ReadFile(cmdline[1], (int)fe[0].Length); 
        }
        catch (IOException e)
        {
            Console.WriteLine("I/O error occured" + e);
            return;
        }
    } 
}

Posted 17-Jan-13 22:57pm

prajwal rao

Updated 17-Jan-13 22:58pm

v2

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Comments

Mohd. Mukhtar 18-Jan-13 5:00am

What error are you getting?

prajwal rao 18-Jan-13 5:04am

Error 1 'System.IO.File': array elements cannot be of static type
Error 2 Cannot declare a variable of static type 'System.IO.File[]
Error 3 Cannot create an instance of the static class 'System.IO.Directory
Error 4 'System.IO.File' does not contain a definition for 'Length' and no extension method 'Length' accepting a first argument of type 'System.IO.File' could be found (are you missing a using directive or an assembly reference?

3 solutions

Solution 4

Brute force approach(requires LINQ):

C#

public static string ReadHeader(string filePath, int maxLen)
{
    return new string(File.ReadAllText(filePath).Take(maxLen).ToArray());
}

By using StreamReader class:

C#

public static string ReadHeader(string filePath, int maxLen)
{
    using (var reader = new StreamReader(filePath))
    {
        int pos = 0;
        char[] buffer = new char[maxLen];
        int n = reader.ReadBlock(buffer, pos, maxLen) - pos;
        return new string(buffer, 0, n);
    }
}

Cheers
Andi

Posted 18-Jan-13 2:47am

Andreas Gieriet

Solution 3

Refer the below link.

Cannot declare a variable of static type 'System.IO.File' in c# .net file upload[^]

http://www.dotnetspider.com/forum/128609-Cannot-declare-variable-static-type-System.IO.File.aspx[^]

This may help you.

Posted 17-Jan-13 23:16pm

Mohd. Mukhtar

Comments

prajwal rao 18-Jan-13 5:28am

ok thank you....

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OriginalGriff · Accepted Answer · 2013-01-17T23:12:00

Solution 1

There are quite a few things you need to look at here, but the compilation error you are probably getting relates to the line:

C#

File[] fe = (new Directory(".")).GetFiles(cmdline[1]);

And tells you that you can't create an array of static objects.

The problem is that the File class is static - there is one and only one instance of it for the entire application, so you cannot under any circumstances create a File variable, and certainly not an array of them - because you can't get at the object to fill it with!

Butthere is a wider problem with this line: GetFiles is a static property of the Directory class, and it doesn't return File objects, it returns an array of strings. So what you actually should have said here is:

C#

string[] fe = Directory.GetFiles(cmdline[1]);

But that isn't actually what you want to do either! There is a much, much easier way to achieve what you want:

C#

if (!File.Exists(cmdline[1]))
    {
    Console.WriteLine(cmdline[1] + ": file not found");
    return;
    }

"sir can u edit the above code and update it please using if(!File.Exists(loadFille)"

Well...it's your homework...so I really shouldn't...

But, ok - if you can tell me exactly what is going on, and why I moved some of your code around!

C#

public static void Main(string[] args)
    {
    String[] cmdline = Environment.GetCommandLineArgs();
    Console.WriteLine("File Reader Using Stream Reader & File Stream \n");
    if (cmdline.Length < 2)
        {
        Console.WriteLine("Usage: " + cmdline[0] + " <input file> ");
        return;
        }
    string loadFile = cmdline[1];

    if (!File.Exists(loadFile))
        {
        Console.WriteLine(loadFile + " : file not found");
        return;
        }
    try
        {
        FileRead fr = new FileRead();
        FileInfo fi = new FileInfo(loadFile);
        fr.ReadFile(loadFile, (int) fi.Length);
        }
    catch (IOException e)
        {
        Console.WriteLine("I/O error occured" + e);
        return;
        }
    }

Posted 17-Jan-13 23:12pm

OriginalGriff

Updated 18-Jan-13 0:30am

v2

Comments

prajwal rao 18-Jan-13 5:20am

but where to put this code sir...

if (!File.Exists(cmdline[1]))
{
Console.WriteLine(cmdline[1] + ": file not found");
return;
}

OriginalGriff 18-Jan-13 5:25am

In place of the existing (bad) code:
File[] fe = (new Directory(".")).GetFiles(cmdline[1]);
if (fe.Length == 0)
{
Console.WriteLine(cmdline[1] + ": file not found");
return;
}

prajwal rao 18-Jan-13 5:27am

ok now i got 1 new error
Error 1 The name 'fe' does not exist in the current context

OriginalGriff 18-Jan-13 5:44am

That is because you are now trying to use the number of elements in a array (that you couldn't declare) as the number of bytes you should read from a file...
I would suggest you look at creating a FileInfo instance...

FileInfo fi = new FileInfo(path);
long numberOfBytesInTheFile = fi.Length;

Can you guess what you should use instead of the "path" parameter? :laugh:

prajwal rao 18-Jan-13 5:53am

sorry sir.... i am new for this language.... just learning.....:( i cant guess it...:(

OriginalGriff 18-Jan-13 5:59am

Yes you can! :laugh:
Think about it: where is the name of the file you want to open?

prajwal rao 18-Jan-13 6:07am

oh ya.....sh*t....:( where i have to specify that sir...???

OriginalGriff 18-Jan-13 6:14am

Instead of the word "path".

Personally, I would create a string variable called "path", or more likely "loadFile" and set the content of the argument into it to start with. Then I would use "loadFile" instead of "cmdline[1]" throughout.

It makes the code a lot more readable if you are looking at:
if (!File.Exists(loadFile)
instead of
if (!File.Exists(cmdline[1]))
and so forth - which makes it easier to get it right! :)
(Think about it - you don't have to think about parameters, but about files. So if you change it later to get a file name from the user when he types it in, you have to change less of your code - which makes it more reliable)

prajwal rao 18-Jan-13 6:20am

sir can u edit the above code and update it please using if(!File.Exists(loadFille)

OriginalGriff 18-Jan-13 6:31am

Answer updated

prajwal rao 18-Jan-13 6:40am

sir its not my homework...
just am learning c# myself.....

OriginalGriff 18-Jan-13 6:47am

I hope you are using a book or similar - "pick it up as you go" is a very bad idea with something as big as .NET. You can miss so much stuff which makes your life easier. For example:
string content = File.ReadAllText(loadFile)
does in one line what your code does in quite a few!

prajwal rao 18-Jan-13 6:53am

ya sir am using book to learn....
is there any different code to read a file other then the above code....???

OriginalGriff 18-Jan-13 7:07am

Loads! There are a whole bunch of File methods (ReadAllLines, ReadAllBytes, and others), there are the Stream methods, the derived streams, and buch of specialised ones - see what I mean by so much stuff?

Have a look at the File class in MSDN - it is the simplest interface to files, but is very powerful.

prajwal rao 18-Jan-13 7:11am

hmmmm ya i have visited it now sir......
can you give me a simplest method to read a file..... very short code.....

OriginalGriff 18-Jan-13 7:51am

I already did:
string content = File.ReadAllText(loadFile);

prajwal rao 18-Jan-13 8:15am

how about this code
using System;
using System.IO;
using System.Text;

class Test
{
public static void Main()
{
string path = @"E:\\new.txt";
using (FileStream fs = File.OpenRead(path))
{
byte[] b = new byte[4096];
UTF8Encoding temp = new UTF8Encoding(true);

while (fs.Read(b, 0, b.Length) > 0)
{
Console.WriteLine(temp.GetString(b));
}
}
}

OriginalGriff 18-Jan-13 8:21am

That should work, but it'll probably be a bit slow - you are retrieving each byte individually, and converting it to a string, which is not necessarily the best way. You might find it quicker to fetch all the bytes at once using File.ReadAllBytes, and then UTF convert the lot.
Plus, if you have a big file, the WriteLines are going to take quite a while! :laugh:

It depends what you are trying to do and why - if you are trying to learn about streams, then try the exercises in your book: they should expand on the material covered in the chapter in a logical progression.

prajwal rao 18-Jan-13 8:24am

well thank you sir..... am trying to read only 4096 bytes data

Orcun Iyigun 18-Jan-13 9:03am

If that worked for you mark his solution as an ANSWER!!!

OriginalGriff 18-Jan-13 9:24am

I understand - but you shouldn't assume you will use the same code for just that. If you expand the use in two weeks time to read 1MB files, you might wish you had written it to run a bit quicker! :laugh:

BC @ CV 18-Jan-13 9:49am

You are a very patient guy. +5

OriginalGriff 18-Jan-13 10:25am

Not really! :laugh:

But sometimes beginners need a little more time and effort...

Andreas Gieriet 18-Jan-13 8:30am

You run into the same wall as I did in the previous thread. He does not read your answers nor does he follow your advise not does he rasonably answer to questions. I'm clue-less. I mean he asks for the simplest file reading C# code, and when you provide, he does not follow up, but jumps to something else. Weird.
Andi