BinaryWriter to overwrite an existing file c#

Question

To write a picture on the memory of my pocket pc i use the following code:

pic = (byte[])myPicutureFromDatabase;
using (var fs = new BinaryWriter(new FileStream(filepath, FileMode.Append, FileAccess.Write)))
{
    fs.Write(pic);
    fs.Flush();
    continue;
}

I wanted to ask you if this method overwrite the file with new values if the file with this name already exist or do nothing because already exist this file? I need to overwrite the file in eventuality that this file already exist but with old value.

FileMode.Append appends data if file exists or creates a new file if file doesn't exist. If you want to overwrite the file, use FileMode.Create — Dmitrii Bychenko
– Dmitrii Bychenko, Commented Jul 31, 2013 at 10:12

Ehsan · Accepted Answer · 2013-07-31 10:19:13Z

From MSDN FileMode.Create

Specifies that the operating system should create a new file. If the file already exists, it will be overwritten. This requires FileIOPermissionAccess.Write permission. FileMode.Create is equivalent to requesting that if the file does not exist, use CreateNew; otherwise, use Truncate. If the file already exists but is a hidden file, an UnauthorizedAccessException exception is thrown.

Where as FileMode.Append

Opens the file if it exists and seeks to the end of the file, or creates a new file. This requires FileIOPermissionAccess.Append permission. FileMode.Append can be used only in conjunction with FileAccess.Write. Trying to seek to a position before the end of the file throws an IOException exception, and any attempt to read fails and throws a NotSupportedException exception.

So, you should use this

pic = (byte[])myPicutureFromDatabase;
using (var fs = new BinaryWriter(new FileStream(filepath, FileMode.Create, FileAccess.Write)))
       {
          fs.Write(pic);
          fs.Flush();
          continue;
        }

Tobia Zambon · Accepted Answer · 2013-07-31 10:09:53Z

1

No it appends the lines, you have specified it by writing FileMode.Append, you should specify FileMode.Create in order to append lines (or create a new file if it not exists)

answered Jul 31, 2013 at 10:09

Tobia Zambon

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1 Comment

user1788654 Over a year ago

thank you, I found the same solution right after posted the question. But thank you for the fast response.

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