How to get the size on disk of a file in c#

Question

Hi

     I want to get the size on disk of a selected file in c#.By using FileInfo.Length i am able to get the file size.But i need "size on disk" in c#.

                    Thanks in advance

Thanks

Chandu.Sanka

Answer 1

With the DriveInfo class.

Regards.

Answer 2

HI  V.Tortola

      when i click  file properties window.below the size property of the file,there is another property as "SIZE ON DISK".I need the value of that property.I don't need hard disk information.

Answer 3

The size on disk is returned by the FileInfo object or the StreamReader base object length property- it will get the value on how many bytes are available to read for that file as its true value.

I'm curious why you need the other property? (Size on disk)

Answer 4

Hi ahmedilyas

   i want to display properties form when i click properties of a file from my application itself.Right now i am able to retrive all the information regarding a file like file type,creation,modified time etc..,There is only one task left.that is "SIZE ON DISK".

Thanks

Chandu.Sanka

Answer 5

The size on disk should be the sum of the size of the clusters that store the file:
  long sizeondisk = clustersize * ((filelength + clustersize - 1) / clustersize);

You'll need to dip into P/Invoke to find the cluster size; GetDiskFreeSpace() returns it.

Answer 6

If you are using ntfs this approach won't work for files with the compressed attribute on.
On such files the 'size on disk' is usually smaller than the actual file size 
   :-)

 

 

Answer 7

The Win32 function GetCompressedFileSize() can get the size of a compressed file. Use File.GetAttributes() to determine whether the file is compressed.

Answer 8

The size on disk should be the sum of the size of the clusters that store the file:
  long sizeondisk = clustersize * ((filelength + clustersize - 1) / clustersize);

You'll need to dip into P/Invoke to find the cluster size; GetDiskFreeSpace() returns it.

This formula is realy stupid and useless because it means that:

clustersize * ((filelength + clustersize - 1) / clustersize)=

= (clustersize /clustersize)* (filelength + clustersize - 1)=

= 1* (filelength + clustersize - 1)=

=filelength + clustersize - 1

and this is not true

Answer 9

You're forgetting that this is a computer program, not a purely mathematical equation.
((filelength + clustersize - 1) / clustersize) is calculated independently and since it's an operation on integers, the result is floored to the closest lower integer.

Therefore what you are saying is incorrect.