distinguish html link and image link like Facebook attach in .NET

like facebook attach link,

when i share a link -> facebook fetch the html page

when i share a image link -> facebook fetch the image

so at server side (.NET, C#), how can i distin开发者_运维百科guish a html link or image link

any help?

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You could try a couple things:

• Do a regex on the URL and check for a file extension. E.g. \.(png|jpg|gif|bmp)$
• Actually retrieve the document, and check the mime type

Also, check answers to this question:

Regex to check if valid URL that ends in .jpg, .png, or .gif

The most recent answer there mentions a library called FastImage.