Fastest way to read file length C#
Solution 1
The natural way to get the file size in .NET is the FileInfo.Length property you mentioned.
I am not sure Stream.Length
is slower (it won't read the whole file anyway), but it's definitely more natural to use FileInfo
instead of a FileStream
if you do not plan to read the file.
Here's a small benchmark that will provide some numeric values:
private static void Main(string[] args)
{
string filePath = ...; // Path to 2.5 GB file here
Stopwatch z1 = new Stopwatch();
Stopwatch z2 = new Stopwatch();
int count = 10000;
z1.Start();
for (int i = 0; i < count; i++)
{
long length;
using (Stream stream = new FileStream(filePath, FileMode.Open))
{
length = stream.Length;
}
}
z1.Stop();
z2.Start();
for (int i = 0; i < count; i++)
{
long length = new FileInfo(filePath).Length;
}
z2.Stop();
Console.WriteLine(string.Format("Stream: {0}", z1.ElapsedMilliseconds));
Console.WriteLine(string.Format("FileInfo: {0}", z2.ElapsedMilliseconds));
Console.ReadKey();
}
Results:
Stream: 886
FileInfo: 727
Solution 2
Both will access the file system metadata rather than reading the whole file. I don't know which is more efficient necessarily, as a rule of thumb I'd say that if you only want to know the length (and other metadata), use FileInfo
- whereas if you're opening the file as a stream anyway, use FileStream.Length
.
jpints14
Updated on June 25, 2022Comments
-
jpints14 almost 2 years
I am using
fs.Length
, wherefs
is aFileStream
.Is this an
O(1)
operation? I would think this would just read from the properties of the file, as opposed to going through the file to find when the seek position has reached the end. The file I am trying to find the length of could easily range from 1 MB to 4-5 GB.However I noticed that there is a
FileInfo
class, which also has aLength
property.Do both of these
Length
properties theoretically take the same amount of time? Or does isfs.Length
slower because it must open theFileStream
first?