c# - Read large files

Question

I tried to read a 2+ gb file in two ways, the first:

var file = File.ReadAllBytes(filepath);

returns an exception, file over 2gb.

Second way:

var file = ReadAllBytes(filepath);

public byte[] ReadAllBytes(string fileName)
{
    byte[] buffer = null;

    using (FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read))
    {
        buffer = new byte[fs.Length];
        fs.Read(buffer, 0, (int)fs.Length);
    }

    return buffer;
}

Exception: "Array dimensions exceeded supported range." My goal is to send the file in the body of http request (using WebClient class).

Any example of how to read large files?

Thanks

Answer 1

You can try this:

public void ProcessLargeFile(string fileName)
{
    int bufferSize = 100 * 1024 * 1024; // 100MB
    byte[] buffer = new byte[bufferSize];
    int bytesRead = 0;

    using (FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read))
    {
        while ((bytesRead = fs.Read(buffer, 0, bufferSize)) > 0)
        {
            if (bytesRead < bufferSize)
            {
                // please note array contains only 'bytesRead' bytes from 'bufferSize'
            }

            // here 'buffer' you get current portion on file 
            // process this
        }
    }
}

That will allow you to process file by 100MB portions, you can change this value to required one.