问题:

using (var writer = File.CreateText(fullFilePath))
{
   file.Write(fileContent);
}

Given the above code, can the file size be known from StreamWriter?

回答1:

Yes, you can, try the following

long length = writer.BaseStream.Length;//will give unexpected output if autoflush is false and write has been called just before

Note: writer.BaseStream.Length property can return unexpected results since StreamWriter doesn't write immediately. It caches so to get expected output you need AutoFlush = true

writer.AutoFlush = true; or writer.Flush();
long length = writer.BaseStream.Length;//will give expected output

回答2:

I think what you are looking for if you need properties of a specific file is FileInfo.

FileInfo info = new FileInfo(fullFilePath);
//Gets the size, in bytes, of the current file.
long size = info.Length;

回答3:

Here you go! Just use the FileInfo class in the System.IO namespace :)

using System.IO;

var fullFilePath = "C:\path\to\some\file.txt";
var fileInfo = new FileInfo(fullFilePath);

Console.WriteLine("The size of the file is: " + fileInfo.Length);