测试C#中是否存在图像

Question

我正在为SiteScope编写诊断页面,我们需要测试的一个区域是,是否可以从Web服务器访问文件/媒体资产的连接.我认为我可以这样做的一种方法是通过代码加载图像并测试以查看IIS状态消息是否为200.

所以基本上我应该能够在站点内导航到这样的文件夹:/media/1/image.jpg并查看它是否返回200 ...如果不抛出异常.

我正在努力弄清楚如何编写这段代码.

任何帮助是极大的赞赏.

谢谢

Answer 1

只需使用HEAD.如果您不需要,无需下载整个图像.这里有一些样板代码.

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

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

Answer 2

您可能还想检查是否有一个OK状态代码(即HTTP 200),并且响应对象中的mime类型与您期望的匹配.你可以沿着这条线延伸

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;
    }
}

Answer 3

您必须处置HTTPWebResponse对象,否则您将遇到问题,因为我有...

    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;
            }
    }

Answer 4

我之前使用过这样的东西,但可能有更好的方法:

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";
}