How to return XML in ASP.NET?
I've found the proper way to return XML to a client in ASP.NET. I think if I point out the wrong ways, it will make the right way more understandable.
Incorrect:
Response.Write(doc.ToString());
Incorrect:
Response.Write(doc.InnerXml);
Incorrect:
Response.ContentType = "text/xml";
Response.ContentEncoding = System.Text.Encoding.UTF8;
doc.Save(Response.OutputStream);
Correct:
Response.ContentType = "text/xml"; //Must be 'text/xml'
Response.ContentEncoding = System.Text.Encoding.UTF8; //We'd like UTF-8
doc.Save(Response.Output); //Save to the text-writer
//using the encoding of the text-writer
//(which comes from response.contentEncoding)
Use a TextWriter
Do not use Response.OutputStream
Do use Response.Output
Both are streams, but Output is a TextWriter. When an XmlDocument saves itself to a TextWriter, it will use the encoding specified by that TextWriter. The XmlDocument will automatically change the xml declaration node to match the encoding used by the TextWriter. e.g. in this case the XML declaration node:
<?xml version="1.0" encoding="ISO-8859-1"?>
would become
<?xml version="1.0" encoding="UTF-8"?>
This is because the TextWriter has been set to UTF-8. (More on this in a moment). As the TextWriter is fed character data, it will encode it with the byte sequences appropriate for its set encoding.
Incorrect:
doc.Save(Response.OutputStream);
In this example the document is incorrectly saved to the OutputStream, which performs no encoding change, and may not match the response's content-encoding or the XML declaration node's specified encoding.
Correct
doc.Save(Response.Output);
The XML document is correctly saved to a TextWriter object, ensuring the encoding is properly handled.
Set Encoding
The encoding given to the client in the header:
Response.ContentEncoding = ...
must match the XML document's encoding:
<?xml version="1.0" encoding="..."?>
must match the actual encoding present in the byte sequences sent to the client. To make all three of these things agree, set the single line:
Response.ContentEncoding = System.Text.Encoding.UTF8;
When the encoding is set on the Response object, it sets the same encoding on the TextWriter. The encoding set of the TextWriter causes the XmlDocument to change the xml declaration:
<?xml version="1.0" encoding="UTF-8"?>
when the document is Saved:
doc.Save(someTextWriter);
Save to the response Output
You do not want to save the document to a binary stream, or write a string:
Incorrect:
doc.Save(Response.OutputStream);
Here the XML is incorrectly saved to a binary stream. The final byte encoding sequence won't match the XML declaration, or the web-server response's content-encoding.
Incorrect:
Response.Write(doc.ToString());
Response.Write(doc.InnerXml);
Here the XML is incorrectly converted to a string, which does not have an encoding. The XML declaration node is not updated to reflect the encoding of the response, and the response is not properly encoded to match the response's encoding. Also, storing the XML in an intermediate string wastes memory.
You don't want to save the XML to a string, or stuff the XML into a string and response.Write a string, because that:
- doesn't follow the encoding specified
- doesn't set the XML declaration node to match
- wastes memory
Do use doc.Save(Response.Output);
Do not use doc.Save(Response.OutputStream);
Do not use Response.Write(doc.ToString());
Do not use 'Response.Write(doc.InnerXml);`
Set the content-type
The Response's ContentType must be set to "text/xml". If not, the client will not know you are sending it XML.
Final Answer
Response.Clear(); //Optional: if we've sent anything before
Response.ContentType = "text/xml"; //Must be 'text/xml'
Response.ContentEncoding = System.Text.Encoding.UTF8; //We'd like UTF-8
doc.Save(Response.Output); //Save to the text-writer
//using the encoding of the text-writer
//(which comes from response.contentEncoding)
Response.End(); //Optional: will end processing
Complete Example
Rob Kennedy had the good point that I failed to include the start-to-finish example.
GetPatronInformation.ashx:
<%@ WebHandler Language="C#" Class="Handler" %>
using System;
using System.Web;
using System.Xml;
using System.IO;
using System.Data.Common;
//Why a "Handler" and not a full ASP.NET form?
//Because many people online critisized my original solution
//that involved the aspx (and cutting out all the HTML in the front file),
//noting the overhead of a full viewstate build-up/tear-down and processing,
//when it's not a web-form at all. (It's a pure processing.)
public class Handler : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
//GetXmlToShow will look for parameters from the context
XmlDocument doc = GetXmlToShow(context);
//Don't forget to set a valid xml type.
//If you leave the default "text/html", the browser will refuse to display it correctly
context.Response.ContentType = "text/xml";
//We'd like UTF-8.
context.Response.ContentEncoding = System.Text.Encoding.UTF8;
//context.Response.ContentEncoding = System.Text.Encoding.UnicodeEncoding; //But no reason you couldn't use UTF-16:
//context.Response.ContentEncoding = System.Text.Encoding.UTF32; //Or UTF-32
//context.Response.ContentEncoding = new System.Text.Encoding(500); //Or EBCDIC (500 is the code page for IBM EBCDIC International)
//context.Response.ContentEncoding = System.Text.Encoding.ASCII; //Or ASCII
//context.Response.ContentEncoding = new System.Text.Encoding(28591); //Or ISO8859-1
//context.Response.ContentEncoding = new System.Text.Encoding(1252); //Or Windows-1252 (a version of ISO8859-1, but with 18 useful characters where they were empty spaces)
//Tell the client don't cache it (it's too volatile)
//Commenting out NoCache allows the browser to cache the results (so they can view the XML source)
//But leaves the possiblity that the browser might not request a fresh copy
//context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
//And now we tell the browser that it expires immediately, and the cached copy you have should be refreshed
context.Response.Expires = -1;
context.Response.Cache.SetAllowResponseInBrowserHistory(true); //"works around an Internet Explorer bug"
doc.Save(context.Response.Output); //doc saves itself to the textwriter, using the encoding of the text-writer (which comes from response.contentEncoding)
#region Notes
/*
* 1. Use Response.Output, and NOT Response.OutputStream.
* Both are streams, but Output is a TextWriter.
* When an XmlDocument saves itself to a TextWriter, it will use the encoding
* specified by the TextWriter. The XmlDocument will automatically change any
* XML declaration node, i.e.:
* <?xml version="1.0" encoding="ISO-8859-1"?>
* to match the encoding used by the Response.Output's encoding setting
* 2. The Response.Output TextWriter's encoding settings comes from the
* Response.ContentEncoding value.
* 3. Use doc.Save, not Response.Write(doc.ToString()) or Response.Write(doc.InnerXml)
* 3. You DON'T want to save the XML to a string, or stuff the XML into a string
* and response.Write that, because that
* - doesn't follow the encoding specified
* - wastes memory
*
* To sum up: by Saving to a TextWriter: the XML Declaration node, the XML contents,
* and the HTML Response content-encoding will all match.
*/
#endregion Notes
}
private XmlDocument GetXmlToShow(HttpContext context)
{
//Use context.Request to get the account number they want to return
//GET /GetPatronInformation.ashx?accountNumber=619
//Or since this is sample code, pull XML out of your rear:
XmlDocument doc = new XmlDocument();
doc.LoadXml("<Patron><Name>Rob Kennedy</Name></Patron>");
return doc;
}
public bool IsReusable { get { return false; } }
}
How to make ASP.NET Core return XML result?
Try this solution
[HttpGet]
[HttpPost]
public ContentResult GetXml(string value)
{
var xml = $"<result><value>{value}</value></result>";
return new ContentResult
{
Content = xml,
ContentType = "application/xml",
StatusCode = 200
};
}
Return complete XML response from ASP .NET Core Web API method
You need to configure XML output formatter like this:
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
services.AddMvc(options =>
{
options.Filters.Add(new ProducesAttribute("text/xml"));
options.OutputFormatters.Add(new XmlSerializerOutputFormatter(new XmlWriterSettings
{
OmitXmlDeclaration = false
}));
}).AddXmlSerializerFormatters();
}
Sample output:
<?xml version="1.0" encoding="utf-8"?>
<ArrayOfString xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<string>value1</string>
<string>value2</string>
</ArrayOfString>
WebAPI to Return XML
If you return a serializable object, WebAPI will automatically send JSON or XML based on the Accept header that your client sends.
If you return a string, you'll get a string.
How to return XML from ASP.NET 4 Web API to ASP.NET Core 2 application?
Update the controller on the server:
public HttpResponseMessage Get()
{
//process the request
.........
string XML="<note><body>Message content</body></note>";
return new HttpResponseMessage()
{
Content = new StringContent(XML, Encoding.UTF8, "application/xml")
};
}
Return XML as HTTP response
I would go for an HttpHandler. This way you circumvent all asp.net control creation etc. which is better for performance and seeing as you will not be outputting any html there's no point in using an actual aspx page.
Returning XML from web API c#
Since you are returning a string from the action, ASP.Net Web API is creating the equivalent XML to represent a string.
Now, if you were to ensure that API uses XML serialization, client can add accept header to the request. Alternatively, you can specify the formatter either the way you have or in the action itself by returning Content using following constructor:
return Content (HttpStatusCodeHere, doc.DocumentElement, Configuration.Formatters.XmlFormatter)
Note that I do not have access to Visual Studio so class/property names might not be accurate.
Return XML From Web Api
For all those that helped. Thanks a ton.
Credit goes to Steve16351 for giving me the hint that got me going in the right direction.
So the problem was in the way I had defined my DataObject class. I needed two changes.
Firstly a paramaterless constructor.
Secondly, I needed to specify property setters. Initially didn't think I needed setters since I would never need to Post data using this class as it's underlying data source is read only.
How do I return Xml with declaration using an ActionResult in ASP.NET MVC?
Maybe try this:
public IActionResult Index()
{
// you need to convert your xml to string
var xmlString = "xml content..";
return this.Content(xmlString, "text/xml");
}
See https://learn.microsoft.com/en-us/previous-versions/aspnet/web-frameworks/dd492713%28v%3dvs.100%29
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