System.ArgumentException when the code get the stream of image file - ASPX - asp.net

Question

i hope anyone to help me in this code that i don't know where,what and why this problem has tookplace !!
i have this code responsible to get images from directory to make a simple watermark for each one, but there is an exception when the code arrive to read the image as streams..
please look at this code :
DirectoryInfo[] dir = new DirectoryInfo[2];
dir[0] = new DirectoryInfo(Server.MapPath("Image/DB/Large/"));
dir[1] = new DirectoryInfo(Server.MapPath("Image/DB/Slide/"));
Image signature = Image.FromFile(Server.MapPath("Image/Design/signature.png"));
for (int i = 0; i < dir.Length; i++)
{
FileInfo[] fs = dir[i].GetFiles("*.jpg");
foreach (FileInfo s in fs)
{
FileStream strm = s.OpenRead();
String name = s.Name;
System.Drawing.Image img = System.Drawing.Image.FromStream(strm);
Graphics g = Graphics.FromImage(img);
g.SmoothingMode = SmoothingMode.HighQuality;
g.DrawImage(signature, new Point(0, 0));
g.Dispose();
strm.Close();
if (i == 0)
{
String v = Server.MapPath("Image/DB/Large/" + name);
img.Save(v);
}
else if (i == 1)
{
String v = Server.MapPath("Image/DB/Slide/" + name);
img.Save(v);
}
}
}
Excception Details :
[ArgumentException: .] System.Drawing.Image.FromStream(Stream stream, Boolean
useEmbeddedColorManagement, Boolean validateImageData) +1065883
System.Drawing.Image.FromStream(Stream stream) +8 Developer.Page_Load(Object sender,
EventArgs e) in f:\.NET Programming\‫FaieqSahwish_V.2.0\Developer.aspx.cs:29
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t,
EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender,
EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

Answer 1

According to the FromStream documentation a ArgumentException is thrown if the stream is not a valid image format or if the stream is null.
Have you verified that neither of these conditions are met for the stream passed into FromStream?

Answer 2

When the exception happens, Visual studio might bring up a debugger. What I'd do is check to make sure your images are what you think they are, and then I'd step through your code and make sure that all the fields are as they should be.
as Ken Henderson said, something(like your FileStream) might be null
Here's a quick sample that i put together myself. It throws no exception.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.IO;
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
DirectoryInfo dir = new DirectoryInfo(#".");
FileInfo[] fi = dir.GetFiles("*.jpg");
FileStream fs = fi[0].OpenRead();
//FileStream fs = new FileStream("New Bitmap Image.jpg", FileMode.Open);
System.Drawing.Image.FromStream(fs);
}
}
}