Image URL validation in C#

Question

How can i check if my image link is valid for both IE and FF? For example this link works just in FF, no image is displayed in IE browser. I checked the image and the color space is RGB. So image space problem is excluded.

Thanks.

Answer 1

Here is a class that will let you validate any kind of URI and will support multi-threaded validation of collection of URIs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Net;
using System.Threading;

namespace UrlValidation
{
    public class UrlValidator
    {
        internal static readonly Hashtable URLVerifications = new Hashtable();
        internal readonly List<ManualResetEvent> Handles = new List<ManualResetEvent>();

        internal void ValidateUrls()
        {
            var urlsToValidate = new[] { "http://www.ok12376876.com", "http//:www.ok.com", "http://www.ok.com", "http://cnn.com" };
            URLVerifications.Clear();
            foreach (var url in urlsToValidate)
                CheckUrl(url);
            if (Handles.Count > 0)
                WaitHandle.WaitAll(Handles.ToArray());

            foreach (DictionaryEntry verification in URLVerifications)
                Console.WriteLine(verification.Value);
        }

        internal class RequestState
        {
            public WebRequest Request;
            public WebResponse Response;
            public ManualResetEvent Handle;
        }

        private void CheckUrl(string url)
        {
            var hashCode = url.GetHashCode();
            var evt = new ManualResetEvent(false);
            Handles.Add(evt);

            if (!Uri.IsWellFormedUriString(url, UriKind.Absolute))
            {
                URLVerifications[hashCode] = "Invalid URL.";
                evt.Set();
                return;
            }

            if (!URLVerifications.ContainsKey(hashCode))
                URLVerifications.Add(hashCode, null);
            // Create a new webrequest to the mentioned URL.   
            var wreq = WebRequest.Create(url);
            wreq.Timeout = 5000; // 5 seconds timeout per thread (ignored for async calls)
            var state = new RequestState{ Request = wreq, Handle = evt };
            // Start the Asynchronous call for response.
            var asyncResult = wreq.BeginGetResponse(RespCallback, state);
            ThreadPool.RegisterWaitForSingleObject(asyncResult.AsyncWaitHandle, TimeoutCallback, state, 5000, true);
        }

        private static void TimeoutCallback(object state, bool timedOut)
        {
            var reqState = (RequestState)state;
            if (timedOut)
            {
                var hashCode = reqState.Request.RequestUri.OriginalString.GetHashCode();
                URLVerifications[hashCode] = "Request timed out.";
                if (reqState.Request != null)
                    reqState.Request.Abort();
            }
        }

        private static void RespCallback(IAsyncResult asynchronousResult)
        {
            ManualResetEvent evt = null;
            int hashCode = 0;
            try
            {
                var reqState = (RequestState)asynchronousResult.AsyncState;
                hashCode = reqState.Request.RequestUri.OriginalString.GetHashCode();
                evt = reqState.Handle;
                reqState.Response = reqState.Request.EndGetResponse(asynchronousResult);
                var resp = ((HttpWebResponse)reqState.Response).StatusCode;
                URLVerifications[hashCode] = resp.ToString();
            }
            catch (WebException e)
            {
                if (hashCode != 0 && string.IsNullOrEmpty((string)URLVerifications[hashCode]))
                    URLVerifications[hashCode] = e.Response == null ? e.Status.ToString() : (int)((HttpWebResponse)e.Response).StatusCode + ": " + ((HttpWebResponse)e.Response).StatusCode;
            }
            finally
            {
                if (evt != null)
                    evt.Set();
            }
        }
    }
}

Hope that helps

Answer 2

Get a copy of fiddler to see the differences in response for each of the browsers. You may find that the headers are wrong and FF is correcting but IE is not.

http://www.fiddler2.com/fiddler2/

Hope this helps