C# 无法将 System.String 转换为 System.Uri
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Cannot Convert System.String to System.Uri
提问by dezkev
I am using the Web Client Class to download files from the internet (Flickr actually).
This works fine as long as I use : WebClient().DownloadData(string), however this locks up the UI as it is Not asynchronous.
我正在使用 Web 客户端类从 Internet 下载文件（实际上是 Flickr）。只要我使用 : 就可以正常工作WebClient().DownloadData(string)，但是这会锁定 UI，因为它不是异步的。
However when I try WebClient().DownloadDatAsync(string), I get a compile error:
"Unable to convert System.String to System.Uri".
但是，当我尝试时WebClient().DownloadDatAsync(string)，出现编译错误：“无法将 System.String 转换为 System.Uri”。
The string MediumUrl returns "http://farm4.static.flickr.com/2232/2232/someimage.jpg"
字符串 MediumUrl 返回 "http://farm4.static.flickr.com/2232/2232/someimage.jpg"
So the question is how do I convert the string "http://farm4.static.flickr.com/2232/2232/someimage.jpg"to a Uri.
所以问题是如何将字符串转换"http://farm4.static.flickr.com/2232/2232/someimage.jpg"为 Uri。
Things I have tried-
我尝试过的事情-
- I have tried to cast it to Uri but that does not work either.
I have tried
Uri myuri = new uri(string)- errors out as above.foreach (Photo photo in allphotos) { //Console.WriteLine(String.Format("photo title is :{0}", photo.Title)); objimage = new MemoryStream(wc.DownloadData(photo.MediumUrl)); images.Add(new Pictures(new Bitmap(objimage), photo.MediumUrl, photo.Title)); }
- 我试图将它转换为 Uri 但这也不起作用。
我试过
Uri myuri = new uri(string)- 错误如上。foreach (Photo photo in allphotos) { //Console.WriteLine(String.Format("photo title is :{0}", photo.Title)); objimage = new MemoryStream(wc.DownloadData(photo.MediumUrl)); images.Add(new Pictures(new Bitmap(objimage), photo.MediumUrl, photo.Title)); }
回答by Thomas Levesque
objimage = new MemoryStream(wc.DownloadData(new Uri(photo.MediumUrl)));
b) I have tried Uri myuri = new uri(string) - errors out as above.
b) 我试过 Uri myuri = new uri(string) - 上面的错误。
This is the usual way to create a Uri from a string... I don't see why it wouldn't work if the string is a valid URI
这是从字符串创建 Uri 的常用方法......如果字符串是有效的 URI，我不明白为什么它不起作用
回答by Daniel Elliott
var yourUri = new UriBuilder(yourString).Uri;
So your example would be:
所以你的例子是：
wc.DownloadDataAsync(new UriBuilder(photo.MediumUrl).Uri);
objimage = new MemoryStream(wc.Result);
You may need to put a check in to see the operation has completed.
您可能需要签入以查看操作已完成。
Hope that helps,
希望有帮助，
Dan
担
回答by Mitch Wheat
If I understand your code correctly, then
如果我正确理解你的代码，那么
wc.DownloadDataAsync(new Uri(photo.MediumUrl));
should work.
应该管用。
回答by Digitalex
This works just fine;
这很好用；
System.Uri uri = new System.Uri("http://farm4.static.flickr.com/2232/2232/someimage.jpg");
By the way; I notice you mistyped the expression new uri(..., with lowercase uri. This is not your problem, is it? Because it should be "new Uri".
顺便一提; 我注意到你错误地输入了表达式 new uri(..., 用小写的 uri。这不是你的问题，是吗？因为它应该是“new Uri”。
回答by Peter Kelly
Okay, so I think if the others have proved your URI is valid in their code and it compiles etc. and you also mention it is generated at runtime - it could be that the UriString you are generating at runtime is invalid and not what you are expecting?
好的，所以我认为如果其他人已经证明您的 URI 在他们的代码中有效并且可以编译等，并且您还提到它是在运行时生成的 - 可能是您在运行时生成的 UriString 无效，而不是您的身份期待？
Instead of letting an exception be thrown for attempting to create a Uri from an invalid string, I would suggest the following method IsWellFormedUriStringon the Uriclass.
我不会因为尝试从无效字符串创建 Uri 而抛出异常，而是建议在Uri类上使用以下方法IsWellFormedUriString。
string uriString = "your_UriString_here";
if (Uri.IsWellFormedUriString(uriString, UriKind.Absolute))
{
Uri uri = new Uri(uriString);
}
else
{
Logger.WriteEvent("invalid uriString: " + uriString);
}
Might help with your debugging also.
也可能有助于您的调试。
