Test to see if an image exists in C#

Question

I am writing a diagnostic page for SiteScope and one area we need to test is if the connection to the file/media assets are accesible from the web server. One way I think I can do this is load the image via code behind and test to see if the IIS status message is 200.

So basically I should be able to navigate to within the site to a folder like this: /media/1/image.jpg and see if it returns 200...if not throw exception.

I am struggling to figure out how to write this code.

Any help is greatly appreciated.

Thanks

What if I want to test a page with URL like http://localhost/homepage and see if there is any missing image in this page ? My initial idea is to read the page using HttpWebRequest, get the Response then look into the content, for each <img> element, spawn another Request. Any different idea ? — Dio Phung
– Dio Phung, Commented Aug 15, 2014 at 4:03
Possible duplicate of How to check if a file exists on an webserver by its URL? — Esko
– Esko, Commented Apr 2, 2019 at 5:33

Greg Dean · Accepted Answer · 2008-10-10 16:26:36Z

53

Just use HEAD. No need to download the entire image if you don't need it. Here some boilerplate code.

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("url");
request.Method = "HEAD";

bool exists;
try
{
    request.GetResponse();
    exists = true;
}
catch
{
   exists = false;
}

answered Oct 10, 2008 at 16:26

Greg Dean

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3 Comments

JL. Over a year ago

Can this method be applied to folders if they exist or not?

Kiquenet Over a year ago

@JL, what folders? filesystem ??

Rudey Over a year ago

Won't this return true for every file, not just images?

VMAtm · Accepted Answer · 2012-05-23 11:59:20Z

22

You might want to also check that you got an OK status code (ie HTTP 200) and that the mime type from the response object matches what you're expecting. You could extend that along the lines of,

public bool doesImageExistRemotely(string uriToImage, string mimeType)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uriToImage);
    request.Method = "HEAD";

    try
    {
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();

        if (response.StatusCode == HttpStatusCode.OK && response.ContentType == mimeType)
        {
            return true;
        }
        else
        {
            return false;
        }   
    }
    catch
    {
        return false;
    }
}

edited May 23, 2012 at 11:59

VMAtm

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answered Oct 10, 2008 at 19:02

Anjisan

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3 Comments

asuciu Over a year ago

I would like to add that if you add a using statement around HttpWebResponse request ... you will make sure your app will not hang after three consecutive requests. This scenario may come up when a BackgroundWorker is used. using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) { //the logic comes here }

asuciu Over a year ago

Also if you get any ProtocolError (The remote server returned an error: (500) Internal Server Error.) change: request.Method="GET";

Shimmy Weitzhandler Over a year ago

What's the mimeType to be specified for image?

Bill Daugherty II · Accepted Answer · 2008-10-25 12:18:10Z

You have to dispose of the HTTPWebResponse object, otherwise you will have issues as I have had...

    public bool DoesImageExistRemotely(string uriToImage)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uriToImage);

            request.Method = "HEAD";

            try
            {
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {

                    if (response.StatusCode == HttpStatusCode.OK)
                    {
                        return true;
                    }
                    else
                    {
                        return false;
                    }
                }
            }
            catch (WebException) { return false; }
            catch
            {
                return false;
            }
    }

beno · Accepted Answer · 2008-10-10 16:31:14Z

6

I've used something like this before, but there's probably a better way:

try
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://somewhere/picture.jpg");
    request.Credentials = System.Net.CredentialCache.DefaultCredentials;
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    myImg.ImageUrl = "http://somewhere/picture.jpg";
}
catch (Exception ex)
{
    // image doesn't exist, set to default picture
    myImg.ImageUrl = "http://somewhere/default.jpg";
}

answered Oct 10, 2008 at 16:31

beno

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Comments

Community · Accepted Answer · 2017-05-23 11:46:24Z

1

If you are getting an exception during the request like "The remote server returned an error: (401) Unauthorized.",

This can be resolved by adding the following line

request.Credentials = new NetworkCredential(username, password);

Question and answer added to this questions from check if image exists on intranet.

edited May 23, 2017 at 11:46

CommunityBot

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answered Nov 2, 2011 at 10:34

jhamm

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Comments

Paulos02 · Accepted Answer · 2013-10-07 15:06:37Z

If url exists like http:\server.myImageSite.com the answer is false too only if imageSize > 0 is true.

  public static void GetPictureSize(string url, ref float width, ref float height, ref string err)
  {
    System.Net.HttpWebRequest wreq;
    System.Net.HttpWebResponse wresp;
    System.IO.Stream mystream;
    System.Drawing.Bitmap bmp;

    bmp = null;
    mystream = null;
    wresp = null;
    try
    {
        wreq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url);
        wreq.AllowWriteStreamBuffering = true;

        wresp = (HttpWebResponse)wreq.GetResponse();

        if ((mystream = wresp.GetResponseStream()) != null)
            bmp = new System.Drawing.Bitmap(mystream);
    }
    catch (Exception er)
    {
        err = er.Message;
        return;
    }
    finally
    {
        if (mystream != null)
            mystream.Close();

        if (wresp != null)
            wresp.Close();
    }
    width = bmp.Width;
    height = bmp.Height;
}

public static bool ImageUrlExists(string url)
{

    float width = 0;
    float height = 0;
    string err = null;
    GetPictureSize(url, ref width, ref height, ref err);
    return width > 0;
}

Jeremy Caney · Accepted Answer · 2024-04-05 00:28:40Z

1

Check if the file exists in the folder where you store the asset on the website.

System.IO.File.Exists(Server.MapPath("~/img/testimg.jpg"));

edited Apr 5, 2024 at 0:28

Jeremy Caney

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answered Apr 4, 2024 at 17:53

Cizzan

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Comments

user25519 · Accepted Answer · 2008-10-10 16:30:08Z

-1

I'd look into an HttpWebRequest instead - I think the previous answer will actually download data, whereas you should be able to get the response without data from HttpWebRequest.

http://msdn.microsoft.com/en-us/library/456dfw4f.aspx until step #4 should do the trick. There are other fields on HttpWebResponse for getting the numerical code if needs be...

hth Jack

answered Oct 10, 2008 at 16:30

user25519

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1 Comment

Greg Dean Over a year ago

The only thing it will download is the response header, which is by definition the "response"

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