Read File in C#

Question

I found a C# source code that read from file which have 1000000 double number. The source code is below.

public void filereader()
{           
    using (BinaryReader b = new BinaryReader(File.Open("C:\\Users\\Hanieh\\Desktop\\nums.txt", FileMode.Open)))
    {
        int length = (int)b.BaseStream.Length;
        byte[] fileBytes = b.ReadBytes(length);

        for (int ii = 0; ii < fileBytes.Length - 32 ; ii++)
        {
            savg1[ii / 2] = (double)(BitConverter.ToInt16(fileBytes, ii) / 20000.0);// inja error index midee
            ii++;
        }
    }
}

when I run source code to read from text file I have an error that related to savg1 index that is out of bound. I debug step by step and result shows size of length= 24000000 but savg1=1000000. my question is here: how this source code work and how I can fix this problem.

First tip: File.ReadAllBytes is a simpler way of reading all the bytes in a file... Now, we can't reproduce this as you haven't shown how you've declared or initialized savg1... it's not clear what you mean by "size of length= 24000000 but savg1=1000000"... if you mean the length of the file is 24000000 but the size of savg is 1000000 then that explains the exception... you need to initialize it to the right size, which looks like it needs to be (fileBytes.Length) - 32 / 2 — Jon Skeet
– Jon Skeet, Commented Sep 15, 2016 at 12:26
declaration of savg1 is : double[] savg1 = new double[1000000]; when alg run: line int length = (int)b.BaseStream.Length; the length value assigned to 24000000 i do not no why! — A.Morshedian
– A.Morshedian, Commented Sep 15, 2016 at 12:33

Dmitrii Bychenko · Accepted Answer · 2016-09-15 12:58:18Z

1

I suggest something like this (File.ReadAllBytes and BitConverter.ToDouble):

  byte[] source = File.ReadAllBytes(@"C:\Users\Hanieh\Desktop\nums.txt");
  double[] data = new double[source.Length / sizeof(double)]; 

  for (int i = 0; i < data.Length; ++i)
    data[i] = BitConverter.ToDouble(source, i * sizeof(double));

answered Sep 15, 2016 at 12:58

Dmitrii Bychenko

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Comments

Jeroen van Langen · Accepted Answer · 2016-09-15 12:40:50Z

0

I would solve it like:

double[] data;

using (BinaryReader b = new BinaryReader(File.Open("C:\\Users\\Hanieh\\Desktop\\nums.txt", FileMode.Open)))
{
    // create array/buffer for the doubles  (filelength / bytes per double)
    data = new double[b.BaseStream.Length / sizeof(double)];

    // read the data from the binarystream
    for (int i = 0; i < data.Length; i++)
        data[i] = b.ReadDouble();
}

MessageBox.Show("doubles read: " + data.Length.ToString());

Although, your file nums.txt implies that it is a textfile. You might not read it as a binary file.

edited Sep 15, 2016 at 12:40

answered Sep 15, 2016 at 12:35

Jeroen van Langen

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