Question

I am trying to save Image at server by callback method when I try to execute code I get exception Demo Code Example: http://catalog.codeproject.com/Articles/17193/Upload-Images-Using-C-JavaScript-and-ASP-NET-2-0-C

Stream s = File.OpenRead(returnValue); in cs file I m geting exception File Not Found

  <input id="File1" runat="server"  onchange="PopulateList(this)" name="File1" type="File" />

<script language="javascript" type="text/javascript">

    var counter = 1;
    var newPath = '';
    var filePath = '';


    function PopulateList(obj) {
        // Upload the image to the server folder 
        filePath = obj.value;
        // calls the server's method using client callbacks    
        CallServer(obj.value, '');
    }

    function ReceiveServerData(rValue) {

        // The new path will contain the path of the image which is inside the server's folder 
        newPath = rValue;
        alert(newPath);
        //CreateNestedElements();

    }
</script>

In Cs File

protected string returnValue = String.Empty;

protected void Page_Load(object sender, EventArgs e)
{
    string[] filePaths = null;

    //HtmlInputHidden hiddenControl = (HtmlInputHidden)Page.FindControl("list");
    //if (!String.IsNullOrEmpty(hiddenControl.Value))
    //{
    //    filePaths = hiddenControl.Value.Split('|');

    //    //SaveFilesToDB(filePaths);

    //}

    // register the callback script 

    string sbReference = ClientScript.GetCallbackEventReference(this, "arg", "ReceiveServerData", "context");

    string cbScript = String.Empty;

    // check if the script is already registered or not 

    if (!ClientScript.IsClientScriptBlockRegistered("CallServer"))
    {

        cbScript = @" function CallServer(arg,context) { " + sbReference + "}";

        ClientScript.RegisterClientScriptBlock(this.GetType(), "CallServer", cbScript, true);

    }
}


public string GetCallbackResult()
{
    string fileName = System.IO.Path.GetFileName(returnValue);

    string path = Server.MapPath("Images/");
    string fullPath = path + fileName;

    Stream s = File.OpenRead(returnValue);

    byte[] buffer = new byte[s.Length];
    s.Read(buffer, 0, (int)s.Length);

    int len = (int)s.Length;

    s.Dispose();
    s.Close();

    FileStream fs = new FileStream(fullPath, FileMode.Create);
    fs.Write(buffer, 0, len);

    Bitmap bmp = new Bitmap(fs);


    if (System.IO.Path.GetExtension(returnValue).Equals(".gif"))
    {
        bmp.Save(fs, ImageFormat.Gif);
    }
    else
    {
        bmp.Save(fs, ImageFormat.Jpeg);
    }

    bmp.Dispose();

    fs.Dispose();
    fs.Close();                      

    return "Images/" + fileName;
}

public void RaiseCallbackEvent(string eventArgument)
{
    if (!String.IsNullOrEmpty(eventArgument))
    {
        returnValue = eventArgument;
    }
}

Answer 1

Unfortunately, the code-project article that you have linked is utterly rubbish – the code will work only if you are using the same machine as client and server and that too only in internet explorer. In other cases, you are bound to get an exception because the the file path that has been sent to server would be local file path on client machine and will not be present on the server machine (causing File.OpenRead to fail as path is invalid on server).

I am not sure exactly as what you want to achieve – you will find plenty of plugins or sample if you want to upload file asynchronously. For example, you may use AJAX toolkit AsyncFileUpload control.