问题
I am trying to get a user's thumbnail from another intranet site but some of them do not follow the pre-defined format meaning I would want to load up a default thumbnail instead.
Whats the best way to check if an image URL is valid?
回答1:
Depending on how you are getting your images a variation of this might work
<html>
<body>
<img src="<dynamic handler url>" alt="My Username" onError="this.src='defaultProfile.jpg';" />
</body>
</html>
This is how you would do it in ASP.NET.
Designer -
<asp:Image ImageUrl="NonexistentImage.Jpg" ID="profileImage" Height="50" Width="50" runat=server />
Code Behind (c#)
profileImage.Attributes["onerror"] = "this.src='http://www.cs.uofs.edu/~olivetoj2/blah.jpg';";
This works perfectly for me.
回答2:
WebRequest webRequest = WebRequest.Create(url);
WebResponse webResponse;
try
{
webResponse = webRequest.GetResponse();
}
catch //If exception thrown then couldn't get response from address
{
return 0;
}
return 1;
回答3:
You can acheive this in jQuery quite easily.
$("#myImage")
.load(function() { alert("it loaded ok") })
.error(function() { $(this).attr("src", alternateImage) });
回答4:
From the code-behind check
File.Exists(Server.MapPath("file path"))
If it returns true then assign the value, otherwise assign your default thumbnail.
来源：https://stackoverflow.com/questions/10812985/asp-net-check-if-imageurl-exists