how to get file size before upload in c#

If you are using Asp File Upload Control than You can use PostedFile.ContentLength property of File Upload Control.


For detailed info, Kindly have a look at following.

MSDN--FileUploadControl.PostedFile.ContentLength Property

Hope it will help. :)

You will need javascript code for that .You can write a function on javascript which will send the file size after uploading a file if file upload .

<asp:fileupload id="fu_Upload" runat="server" onchange="javascript:getFileSize(this);" xmlns:asp="#unknown">

function getFileSize(input) {
var file = input.files[0];
return file.size;
}

try this

using System;
using System.IO;

class Program
{
    static void Main()
    {
    // The name of the file
    const string fileName = "test.txt";

    // Create new FileInfo object and get the Length.
    FileInfo f = new FileInfo(fileName);
    long s1 = f.Length;

    // Change something with the file.
    File.AppendAllText(fileName, " More characters.");

    // Create another FileInfo object and get the Length.
    FileInfo f2 = new FileInfo(fileName);
    long s2 = f2.Length;

    // Print out the length of the file before and after.
    Console.WriteLine("Before and after: " + s1.ToString() +
        " " + s2.ToString());

    // Get the difference between the two sizes.
    long change = s2 - s1;
    Console.WriteLine("Size increase: " + change.ToString());
    }
}