Question

I was trying to test a resumable download using c#. I found that add range will help by looking at some blogs. But in the following code add range have no meaning.
Guys Suggest me how to solve the issue.
What method will be effective to make a Resumable download??

HttpWebRequest myrequest = null;
    HttpWebResponse myresponse = null;
    private int interval=2048;
    public bool set_url(string todonwloads,string tosaves)
    {
        this.todownload = todonwloads;
        this.tosave = tosaves;
        return true;
    }
    public bool start_download()
    {
        myrequest = (HttpWebRequest)WebRequest.Create(this.todownload);
       // it the following code. 
       //If i dont write addrange. It will download same portion of the file.
        myrequest.AddRange(4000,8000);

        try
        {
            myresponse = (HttpWebResponse)myrequest.GetResponse();
            if (myresponse.StatusCode == HttpStatusCode.OK)
            {
                Stream ReceiveSteam = myresponse.GetResponseStream();
                FileStream fs = new FileStream(
                                        this.tosave, 
                                        FileMode.Create, 
                                        FileAccess.Write, 
                                        FileShare.None);
                int reads;
                byte[] buffer = new byte[this.interval];
                while ((reads = ReceiveSteam.Read(
                                         buffer, 
                                         0, 
                                         this.interval)) > 0)
                {
                    fs.Write(buffer, 0, reads);
                }
                return true;
            }


        }
        catch (WebException ex)
        {

            throw ex;
        }
        finally
        {
            if (myresponse != null)
            {
                myresponse.Close();
            }
        }
        return false;

    }

Answer 1

You currently create and overwrite the file every time you download a section of the file:

//            Overwrites the file each time -\/
... = new FileStream(this.tosave, FileMode.Create, ...

You instead need to open or create the file using FileMode.OpenOrCreate, then seek to the last section of the file you wrote to:

// seek to the last end offset, you'll need to save this somehow
fs.Seek(lastOffset, SeekOrigin.Begin);

int reads;
byte[] buffer = new byte[this.interval];
while ((reads = ReceiveSteam.Read(buffer, 0, this.interval)) > 0)
{
    fs.Write(buffer, 0, reads);
    lastOffset += reads;
}