I am using webclient to dowlnoad a file. I am calculating the progress percentage as below

1. I know the filesize (I read it from the database table) of the file going to be downloaded.

2. I am depending on the BytesRecieved property of WebClient to know the total bytes fetched during download.

3. The algorithm I am using is double dProgress = (e.BytesReceived / FileSize)*100); to calculate the progress percentage.

However i am not getting correct progress percentage to update the progress bar.

Is there any method to calculate progress开发者_C百科 percentage?

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Look at the following line: double dProgress = (e.BytesReceived / FileSize)*100)

If both e.BytesReceived and FileSize are integers then you will always have 0 * 100 = 0.

Make something like this:

double dProgress = ((double)e.BytesReceived / FileSize)*100.0

It is because / does integer division when dividing two integers. But you don't want that. So you convert one of the variables to double.

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BytesReceived and FileSize most probably are integers so you need to calculate progress this way:

double dProgress = 100.0 * e.BytesReceived / FileSize;

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If you are handling the DownloadProgressChanged event when doing an asynchronous download, the event args already has a ProgressPercentage on it, so there is no point in re-inventing it. A contrived example:

var client = new WebClient();
var reset = new ManualResetEvent(false);
client.DownloadProgressChanged += (s, e) => Console.WriteLine("{0} percent complete", e.ProgressPercentage);
client.DownloadFileCompleted += (s, e) => reset.Set();
client.DownloadFileAsync(new Uri("http://myfilepathhere.com"), "file.name");
//Block till download completes
reset.WaitOne();

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The problem is that both numbers are integers. When you devide them, they become smaller than 1, so they round down to 0. Typecast them to make the result a float:

double dProgress = ((double)e.BytesReceived / FileSize)*100)

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This is a very tricky problem with basic arithmetic and casting in C#.

Solution

First store the result of integer division in a double variable. And then type cast that to an integer.

int x = 5, y = 10, answer;
double ansDouble;
answer = (int)(x / y) * 100; //percentage calculation
Console.WriteLine("percentage={0}", answer);
//>output percentage=0

answer = (int)((double)x / y) * 100; //percentage calculation
Console.WriteLine("percentage={0}", answer);
//>output percentage=0

answer = (int)((double)x / (double)y) * 100; //percentage calculation
Console.WriteLine("x={0}", answer);
//>output percentage=0

answer = (int)(x/(double)y) * 100; //percentage calculation
Console.WriteLine("x={0}", answer);
//>output percentage=0

ansDouble = ((double)x / y) * 100;
answer = (int)ansDouble;
Console.WriteLine("percentage={0}", answer);
//>output percentage=50

Points to note

Turns out that x/y = 0, for any values of x and y as long as they are integers We can't solve this in one line by any casting combinations

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Try this:

WebClient Client = new WebClient();
Client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);

...

  void ProgressChanged(object sender, DownloadProgressChangedEventArgs e) {

            double bytesIn = double.Parse(e.BytesReceived.ToString());
            double totalBytes = double.Parse(e.TotalBytesToReceive.ToString());
            double percentage = bytesIn / totalBytes * 100;
            int percente = int.Parse(Math.Truncate(percentage).ToString());
            progressBar.Value = percente;
        }

Or just using the ProgressPercentage value.

 void ProgressChanged(object sender, DownloadProgressChangedEventArgs e) {
           progressBar.Value = e.ProgressPercentage; 
  }