I have implemented a Restful web service in C# .Net and I want to enable users to upload images via this.
What I currently have is a service that only accepts text data. Ideally I need to get an image from the user and store it in my database.
[OperationContract]
[WebInvoke(UriTemplate = "/{key}", Method = "POST")]
ResponseStatus InsertSensor(string key, Image image);
My question what is the most efficient way to do this?
Many Thanks,
An image is not something you can transmit down a wire.
Instead, you need to encode the image into a stream or byte array (probably using PNG or JPEG).
The client would then send these bytes to the server, and the server would store it in the database.
Sample project from MSDN: ASP.NET Web API: File Upload and Multipart MIME
Here's another write-up that might be useful: http://blogs.msdn.com/b/henrikn/archive/2012/03/01/file-upload-and-asp-net-web-api.aspx
You could allow the users to post the image to a http handler as described in this question.
Related
I am preparing CRUD endpoint for posts (like from social media) in my API (.NET 6, Swagger UI, MongoDb). POST endpoint takes string message and IFormFile with image and save it in db - image is being saved as byte array. User could send a post only with message, only with image or with both of them in the same time. Everything went smoth till the GET endpoint.
In case of returning one of them its fine. In case of returing both the message and the image there is a problem, because I cannot return FileContentResult with image in the same time with string message. I was about to return the message in response header, but I am not sure if its a good idea. Other possible way is to just return message property and image as e.g. stirng. One other way is to just temporarly store the image phisically and send just an url to it. I am not convinced to any of the solutions I figured out.
Could you please tell me, how you see it? Maybe you have faced similar situation in the past?
Kind regards
After searching in google and here, i saw the popular approach is to convert the image to byte array and then to base64 string. this part was easy, but sending it and receiving it over HTTP is harder, and I can't find an easy way to do it.
I have 2 main question which depend one another
Send with android on HTTP:
Android 6 deprecated HttpClient, so i don't want to use that.
I thought to use Volley but i cant figure out how to make it work right.
Can you please give me an example of code to transfer it in a simple and elegant way which will be easy to intercept with C#?
Receive with C# and use of web service:
I'm not sure what is the best way to implement it? Should I create a web service method? in case i should, how can i intercept the post request? Should I create a new page to handle only this part. this way i know how to handle the request.
Edit:
I managed to create a request using HttpClient, but the base64 string after converting the file made the URI too long.
any other ideas?
I found here a post for uploading files from Android to ASP.NET Web API. However the HTTPClient was used for handling HTTP request but I think you can use code as reference.
Found the simple and elegant solution i wanted!
I use loopj library, "android-async-http" for sending files with 3-4 lines.
Then i get the request to a new aspx file in my ASP.NET server, and save it using "Request.Files" object.
This is my first time developing this kind of system, so many of these concepts are very new to me. Any and all help would be appreciated. I'll try to sum up what I'm doing as efficiently as possible.
Background: I have a web application running AngularJS with Bootstrap. The app communicates with the server and DB through a web service programmed using C#. On the site, users can upload files and reference them later using direct links. There's no restriction to file type (yet), so just about anything is allowed.
My Goal: Having direct links creates a big security problem for me, since the documents/images are supposed to be private data. What I would prefer to do is validate a user's credentials when the link is clicked, then load the file in the browser using a more generic url path.
--Example--
"mysite.com/attachments/1" ---> (Image)
--instead of--
"mysite.com/data/files/importantImg.jpg"
Where I'm At: Not very far. My first thought was to add a page that sends the server request and receives a file byte stream along with mime type that I can reassemble and present to the user. However, I have no idea if this is possible using a web service that sends JSON requests, nor do I have a clue about how the reassembling process would work client-side.
Like I said, I'll take any and all advice. I'd love to learn more about this subject for future projects as well, but for now I just need to be pointed in the right direction.
Your first thought is correct, for it, you need to use the Response object, and more specifically the AddHeader and Write functions. Of course this will be a different page that will only handle file downloads, so it will be perfectly fine in your JSON web service.
I don't think you want to do this with a web service. Just use a regular IHttpHandler to perform the validation and return the data. So you would have the URL "attachments/1" get rewritten to "attachments/download.ashx?id=1". When you've verified access, write the data to the response stream. You can use the Content Disposition header to set the file name.
I am using WebClient.UploadFileAsync to upload local files to a web server and I would also like to pass some parameters with the post as well. I would like to send a few fields that will tell the PHP code on the server specific locations on where to save the uploaded files.
I tried to put the fields directly into the url, for example:
WebClient client = new WebClient();
Uri uri = new Uri("http://example.com/upload.php?field1=test");
client.UploadFileAsync(uri, "POST", "c:\test.jpg");
The PHP code returns false for isset($_REQUEST['field1']).
Thank you for any suggestions.
NOTE: this question was also asked in very similar format for vb.net a while back, but it did not get any answers,
WebClient's UploadFile is designed to send only a file (as byte[]) as part of request. From my understanding, UploadFile method closes the request stream after writing the binaries.
In your scenario, you actually request is has two parts 1. file as byte[] 2. the file name as string.
To do this, you have to use HttpWebRequest or any other high level class capable of creating request.
Refer to the post http://www.codeproject.com/KB/cs/uploadfileex.aspx?display=Print
which does a similar job
This article goes into detail about what is needed to accomplish posting of fields while uploading files using WebClient.
Unfortunately, most file upload scenarios are HTML form based and may
contain form fields in addition to the file data. This is where
WebClient falls flat. After review of the source code for WebClient,
it is obvious that there is no possibility of reusing it to perform a
file upload including additional form fields.
So, the only option is to create a custom implementation that conforms
to rfc1867, rfc2388 and the W3C multipart/form-data specification that
will enable file upload with additional form fields and exposes
control of cookies and headers.
I would look into using the QueryString property of the WebClient to set the value of field1 (as well as any other QueryString parameters to the request).
NameValueCollection query = new NameValueCollection();
query.Add("field1", "test");
client.QueryString = query;
Reference: http://msdn.microsoft.com/en-us/library/system.net.webclient.querystring(v=VS.100).aspx
I have a device that uses a custom scripting language. This language provides the capability to set http request headers then perform a post to a URL. The server that the device communicates with is running .net, and I would like the handler on the server to retrieve data from the device by simply pulling it from the Request.Files[] collection. To do this, does the device need to support multipart posting or is it possible for the uploaded content to show up in the Files collection by simply setting a number of headers then sending the data?
I'm not a linux guy, but I did a search and I found this. Does it help at all? (see section 4.3)
http://curl.haxx.se/docs/httpscripting.html
If you mean that at the server end you want the file(s) to be readable via HttpRequest.Files, then I believe so.
I think the format that this expects is based on the File Upload RFC and therefore if you follow the standard procedure for submitting a file upload then it'll work.
As to how you go about formatting the request from your device - I'm afraid I can't help on that one. Assuming you can format an Http Post, writing any headers you need and then formatting the Post body with the file content, it'll work, though.
In order for .Net to be able to read a file posted to a header it must be in the multipart posting format. Otherwise it will just be text noise in the header and .Net won't know what to do with it.