How to read large file (up 4 GB) and convert to byte?

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C#6.0

Hi.
I want to read files with high volume and the a variable Byte[] put.

Below code does not work
byte[] bytes = System.IO.File.ReadAllBytes(filename);

OR

private byte [] StreamFile(string filename)
{
FileStream fs = new FileStream(filename, FileMode.Open,FileAccess.Read);

// Create a byte array of file stream length
byte[] ImageData = new byte[fs.Length];

//Read block of bytes from stream into the byte array
fs.Read(ImageData,0,System.Convert.ToInt32(fs.Length));

//Close the File Stream
fs.Close();
return ImageData; //return the byte data
}

OR

Stream dest = ...
using(Stream source = File.OpenRead(path)) {
byte[] buffer = new byte[2048];
int bytesRead;
while((bytesRead = source.Read(buffer, 0, buffer.Length)) > 0) {
dest.Write(buffer, 0, bytesRead);
}
}

What I have tried:

How To Read Large File (Up 4 GB) And Convert To Byte?