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A C# Http Multipart/form-data parser that works correctly on binary data and very large files.
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Http Multipart Parser

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Release Notes NuGet (stable) MyGet (prerelease)
GitHub release Nuget MyGet Pre Release

About

The Http Multipart Parser does it exactly what it claims on the tin: parses multipart/form-data. This particular parser is well suited to parsing large data from streams as it doesn't attempt to read the entire stream at once and procudes a set of streams for file data.

Installation

The easiest way to include HttpMultipartParser in your project is by adding the nuget package to your project:

PM> Install-Package HttpMultipartParser

.NET framework suport

The parser was built for and tested on NET 4.6.1, NET 4,7,2 and NETSTANDARD 2.0. Versions 2.2.4 was the last version of HttpMultipartParser that supported older .NET platforms such as NET 4.5 and NETSTANDARD 1.3.

Usage

Non-Streaming (Simple, don't use on very large files)

  1. Parse the stream containing the multipart/form-data by invoking MultipartFormDataParser.Parse (or it's asynchronous counterpart MultipartFormDataParser.ParseAsync).
  2. Access the data through the parser.

Streaming (Handles large files)

  1. Create a new StreamingMultipartFormDataParser with the stream containing the multipart/form-data
  2. Set up the ParameterHandler and FileHandler delegates
  3. Call parser.Run() (or it's asynchronous counterpart parser.RunAsync())
  4. The delegates will be called as data streams in.

Examples

Single file

// stream:
-----------------------------41952539122868
Content-Disposition: form-data; name="username"

example
-----------------------------41952539122868
Content-Disposition: form-data; name="email"

example@data.com
-----------------------------41952539122868
Content-Disposition: form-data; name="files[]"; filename="photo1.jpg"
Content-Type: image/jpeg

ExampleBinaryData012031203
-----------------------------41952539122868--

// ===== Simple Parsing ====
// You can parse synchronously:
var parser = MultipartFormDataParser.Parse(stream);

// Or you can parse asynchronously:
var parser = await MultipartFormDataParser.ParseAsync(stream).ConfigureAwait(false);

// From this point the data is parsed, we can retrieve the
// form data using the GetParameterValue method.
var username = parser.GetParameterValue("username");
var email = parser.GetParameterValue("email")

// Files are stored in a list:
var file = parser.Files.First();
string filename = file.FileName;
Stream data = file.Data;

// ==== Advanced Parsing ====
var parser = new StreamingMultipartFormDataParser(stream);
parser.ParameterHandler += parameter => DoSomethingWithParameter(parameter);
parser.FileHandler += (name, fileName, type, disposition, buffer, bytes) =>
{
    // Write the part of the file we've recieved to a file stream. (Or do something else)
    filestream.Write(buffer, 0, bytes);
}

// You can parse synchronously:
parser.Run();

// Or you can parse asynchronously:
await parser.RunAsync().ConfigureAwait(false);

Multiple Parameters

// stream:
-----------------------------41952539122868
Content-Disposition: form-data; name="checkbox"

likes_cake
-----------------------------41952539122868
Content-Disposition: form-data; name="checkbox"

likes_cookies
-----------------------------41952539122868--

// ===== Simple Parsing ====
// You can parse synchronously:
var parser = MultipartFormDataParser.Parse(stream);

// Or you can parse asynchronously:
var parser = await MultipartFormDataParser.ParseAsync(stream).ConfigureAwait(false);

// From this point the data is parsed, we can retrieve the
// form data from the GetParameterValues method
var checkboxResponses = parser.GetParameterValues("checkbox");
foreach(var parameter in checkboxResponses)
{
    Console.WriteLine("Parameter {0} is {1}", parameter.Name, parameter.Data)
}

Multiple Files

// stream:
-----------------------------41111539122868
Content-Disposition: form-data; name="files[]"; filename="photo1.jpg"
Content-Type: image/jpeg

MoreBinaryData
-----------------------------41111539122868
Content-Disposition: form-data; name="files[]"; filename="photo2.jpg"
Content-Type: image/jpeg

ImagineLotsOfBinaryData
-----------------------------41111539122868--

// ===== Simple Parsing ====
// You can parse synchronously:
var parser = MultipartFormDataParser.Parse(stream);

// Or you can parse asynchronously:
var parser = await MultipartFormDataParser.ParseAsync(stream).ConfigureAwait(false);

// Loop through all the files
foreach(var file in parser.Files)
{
    Stream data = file.Data;

    // Do stuff with the data.
}

// ==== Advanced Parsing ====
var parser = new StreamingMultipartFormDataParser(stream);
parser.ParameterHandler += parameter => DoSomethingWithParameter(parameter);
parser.FileHandler += (name, fileName, type, disposition, buffer, bytes) =>
{
    // Write the part of the file we've recieved to a file stream. (Or do something else)
    // Assume that filesreamsByName is a Dictionary<string, FileStream> of all the files
    // we are writing.
    filestreamsByName[name].Write(buffer, 0, bytes);
};
parser.StreamClosedHandler += () 
{
    // Do things when my input stream is closed
};

// You can parse synchronously:
parser.Run();

// Or you can parse asynchronously:
await parser.RunAsync().ConfigureAwait(false);

Licensing

This project is licensed under MIT.

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