The Mysterious Invalid Parameter Used Error

Recently I was trying to write a little C# function for cropping images. I expected it to be a quick 5 minute task but I ended up spending a huge amount of time getting it to work correctly. I kept getting a very stubborn and mysterious error - “Invalid Parameter Used” - whenever I tried to save my newly cropped image by doing bitmap.Save(). I tried various suggestions I found on forums and blogs to no avail.

Finally I figured out what the problem was. I was encapulatning the Bitmap and Graphics objects inside a “using” statement. So the Bitmap object was being prematurely disposed before I returned it back to the caller.

So in the end my solution looked like this. I just god rid of the “usings”.

public Bitmap CropImage(Image image, Rectangle cropRect)
{
    Bitmap bitmap = new Bitmap(cropRect.Width, cropRect.Height, PixelFormat.Format24bppRgb);
    bitmap.SetResolution(image.HorizontalResolution, image.VerticalResolution);
    Graphics graphics = Graphics.FromImage(bitmap);
    graphics.DrawImage(image, 0, 0, cropRect, GraphicsUnit.Pixel);
    return bitmap;
}

Usage -
Bitmap croppedBmp = CropImage(”~/uploads/test.jpg”, new Rectangle(x, y, width, height));
croppedBmp.Save();

Moral of the story: If you are getting this error while calling Bitmap.Save() then make sure you are not disposing your Bitmap object prematurely. Hope this helps.

How to unzip files in .NET using SharpZipLib

SharpZipLib is a great open source library for handeling all kinds of gzip/zip compression/decompression. More Info - http://www.icsharpcode.net/OpenSource/SharpZipLib/

In the following example I’m passing the HtmlInputFile object directly into the ZipInputStream to decompress the PostedFile and save its contents on the server.

.
.
using System.IO;    
using ICSharpCode.SharpZipLib.Zip
.
.
private void UnzipAndSave(HtmlInputFile objFileUpload)
{
    ZipInputStream s = new ZipInputStream(objFileUpload.PostedFile.InputStream);

    ZipEntry theEntry;
    string virtualPath = "~/uploads/";
    string fileName = string.Empty;
    string fileExtension = string.Empty;
    string fileSize = string.Empty;

    while ((theEntry = s.GetNextEntry()) != null)
    {
        fileName = Path.GetFileName(theEntry.Name);
        fileExtension = Path.GetExtension(fileName);

        if (!string.IsNullOrEmpty(fileName))
        {
            try
            {
                FileStream streamWriter = File.Create(Server.MapPath(virtualPath + fileName));
                int size = 2048;
                byte[] data = new byte[2048];

                do
                {
                    size = s.Read(data, 0, data.Length);
                    streamWriter.Write(data, 0, size);
                } while (size > 0);

                fileSize = Convert.ToDecimal(streamWriter.Length / 1024).ToString() + ” KB”;

                streamWriter.Close();

                //Add custom code here to add each file to the DB, etc.
            }
            catch (Exception ex)
            {
                Response.Write(ex.ToString());
            }
        }
    }

    s.Close();
}

How to manipulate video in .NET using ffmpeg

In this case I’m resizing the video and converting it to FLV format. For more ffmpeg commandline options - http://ffmpeg.mplayerhq.hu/ffmpeg-doc.html

private void ConvertVideo(string srcURL, string destURL)
{
    string ffmpegURL = "~/project/tools/ffmpeg.exe";
    DirectoryInfo directoryInfo = new DirectoryInfo(Path.GetDirectoryName(Server.MapPath(ffmpegURL)));

    ProcessStartInfo startInfo = new ProcessStartInfo();
    startInfo.FileName = Server.MapPath(ffmpegURL);
    startInfo.Arguments = string.Format("-i \"{0}\" -s 368x216 -aspect 1.7777 \"{1}\"", srcURL, destURL);
    startInfo.WorkingDirectory = directoryInfo.FullName;
    startInfo.UseShellExecute = false;
    startInfo.RedirectStandardOutput = true;
    startInfo.RedirectStandardInput = true;
    startInfo.RedirectStandardError = true;

    using (Process process = new Process())
    {
        process.StartInfo = startInfo;

        try
        {
            process.Start();
            StreamReader standardOutput = process.StandardOutput;
            StreamWriter standardInput = process.StandardInput;
            StreamReader standardError = process.StandardError;
            process.WaitForExit();

            lblError.Text = standardError.ReadToEnd();
            lblOutput.Text = standardOutput.ReadToEnd();
        }
        catch (Exception ex)
        {
            Response.Write(ex.ToString());
        }
    }
}

Event Driven Developement using ASP.NET & C#

Until recently I wasn’t entirely familiar with the concepts of Event Driven Programming, Event Bubbling, etc. Being a .NET developer I’ve been exposed to events and delegates but I never really understood the concept in its entirety. Somehow I had a hard time readily finding good sources online focusing on event driven programming especially using ASP.NET/C#. But I had to get myself more familiarized with the concept since I need to use a lot of that in my current project. So after doing some digging I found couple of good links which explain the concept quite well -

• Delegates and Events in C# / .NET
• Event Driven ASP.NET Development with C#

Hope that helps.

10 ASP.NET Performance and Scalability Secrets

Very good article. Covers all the following topics:

• ASP.NET Pipeline optimization
• ASP.NET Process configuration optimization
• Things you must do for ASP.NET before going live
• Content Delivery Network
• Caching AJAX calls on browser
• Making best use of Browser Cache
• On demand progressive UI loading for fast smooth experience
• Optimize ASP.NET 2.0 Profile provider
• How to query ASP.NET 2.0 Membership tables without bringing down the site
• Prevent Denial of Service (DOS) attack

http://www.codeproject.com/KB/aspnet/10ASPNetPerformance.aspx