HttpContent Class

Definition

public ref class HttpContent abstract : IDisposable

public abstract class HttpContent : IDisposable

type HttpContent = class
 interface IDisposable

Public MustInherit Class HttpContent
Implements IDisposable

Inheritance

Object

HttpContent

Derived

System.Net.Http.ByteArrayContent

System.Net.Http.Json.JsonContent

System.Net.Http.MultipartContent

System.Net.Http.ReadOnlyMemoryContent

System.Net.Http.StreamContent

Implements

IDisposable

Examples

The following example shows a custom implementation of HttpContent. Some methods, despite being defined as virtual and not abstract, should still be overridden in the implementation for optimal behavior.

public class MyContent : HttpContent
{
 private readonly string _data;
 public MyContent(string data)
 {
 _data = data;
 }

 // Minimal implementation needed for an HTTP request content,
 // i.e. a content that will be sent via HttpClient, contains the 2 following methods.
 protected override bool TryComputeLength(out long length)
 {
 // This content doesn't support pre-computed length and
 // the request will NOT contain Content-Length header.
 length = 0;
 return false;
 }

 // SerializeToStream* methods are internally used by CopyTo* methods
 // which in turn are used to copy the content to the NetworkStream.
 protected override Task SerializeToStreamAsync(Stream stream, TransportContext? context)
 => stream.WriteAsync(Encoding.UTF8.GetBytes(_data)).AsTask();

 // Override SerializeToStreamAsync overload with CancellationToken
 // if the content serialization supports cancellation, otherwise the token will be dropped.
 protected override Task SerializeToStreamAsync(Stream stream, TransportContext? context, CancellationToken cancellationToken)
 => stream.WriteAsync(Encoding.UTF8.GetBytes(_data), cancellationToken).AsTask();

 // In rare cases when synchronous support is needed, e.g. synchronous CopyTo used by HttpClient.Send,
 // implement synchronous version of SerializeToStream.
 protected override void SerializeToStream(Stream stream, TransportContext? context, CancellationToken cancellationToken)
 => stream.Write(Encoding.UTF8.GetBytes(_data));

 // CreateContentReadStream* methods, if implemented, will be used by ReadAsStream* methods
 // to get the underlying stream and avoid buffering.
 // These methods will not be used by HttpClient on a custom content.
 // They are for content receiving and HttpClient uses its own internal implementation for an HTTP response content.
 protected override Task<Stream> CreateContentReadStreamAsync()
 => Task.FromResult<Stream>(new MemoryStream(Encoding.UTF8.GetBytes(_data)));

 // Override CreateContentReadStreamAsync overload with CancellationToken
 // if the content serialization supports cancellation, otherwise the token will be dropped.
 protected override Task<Stream> CreateContentReadStreamAsync(CancellationToken cancellationToken)
 => Task.FromResult<Stream>(new MemoryStream(Encoding.UTF8.GetBytes(_data))).WaitAsync(cancellationToken);

 // In rare cases when synchronous support is needed, e.g. synchronous ReadAsStream,
 // implement synchronous version of CreateContentRead.
 protected override Stream CreateContentReadStream(CancellationToken cancellationToken)
 => new MemoryStream(Encoding.UTF8.GetBytes(_data));
}

Remarks

There are various HTTP contents that can be used. These include the following.

1. ByteArrayContent - A content represented by a byte array, also serves as a base class for StringContent and FormUrlEncodedContent.

2. StringContent - A string-based content, by default serialized as text/plain Content-Type with UTF-8 encoding.

3. FormUrlEncodedContent - A content with name/value tuples serialized as application/x-www-form-urlencoded Content-Type.

4. MultipartContent - A content that can serialize multiple different HttpContent objects as multipart/* Content-Type.

5. JsonContent - A content that serializes objects as application/json Content-Type with UTF-8 encoding by default.

HTTP content class can be derived by a user to provide custom content serialization logic.