AuthenticationHeaderValue Class

Overview

The AuthenticationHeaderValue class provides a way to represent and manipulate HTTP authentication headers. HTTP authentication headers are used to provide credentials or other information required to authenticate a client request to a server. This class parses and formats standard HTTP authentication header strings, such as "Basic", "Digest", "Bearer", etc., along with their associated parameters.

Key aspects include:

• Representing the authentication scheme (e.g., "Basic").
• Storing and retrieving scheme-specific parameters.
• Parsing strings into a structured object.
• Formatting the object back into a string representation.

This class is immutable, meaning once an instance is created, its properties cannot be changed.

Syntax

public sealed class AuthenticationHeaderValue

Members

Constructors

• AuthenticationHeaderValue(string scheme)
  (string scheme)
  Initializes a new instance of the AuthenticationHeaderValue class with the specified authentication scheme.
• AuthenticationHeaderValue(string scheme, object[] parameters)
  (string scheme, object[] parameters)
  Initializes a new instance of the AuthenticationHeaderValue class with the specified authentication scheme and parameters.

Properties

• Scheme
  public string Scheme { get; }
  Gets the HTTP authentication scheme.
• Parameters
  public ICollection> Parameters { get; }
  Gets the parameters for the HTTP authentication scheme.

Methods

• ToString()
  public override string ToString()
  Returns a string representation of the current object.
• Equals(object obj)
  public override bool Equals(object obj)
  Determines whether the specified object is equal to the current object.
• GetHashCode()
  public override int GetHashCode()
  Serves as the default hash function.
• Parse(string value)
  public static AuthenticationHeaderValue Parse(string value)
  Parses a string into an AuthenticationHeaderValue instance.
• TryParse(string value, out AuthenticationHeaderValue result)
  public static bool TryParse(string value, out AuthenticationHeaderValue result)
  Tries to parse a string into an AuthenticationHeaderValue instance without throwing an exception.

Operators

• ==
  public static bool operator ==(AuthenticationHeaderValue left, AuthenticationHeaderValue right)
  Compares two AuthenticationHeaderValue objects for equality.
• !=
  public static bool operator !=(AuthenticationHeaderValue left, AuthenticationHeaderValue right)
  Compares two AuthenticationHeaderValue objects for inequality.

Remarks

The AuthenticationHeaderValue class is primarily used with the HttpClient class to set the Authorization header for outgoing HTTP requests. It allows for structured representation of authentication schemes like Basic, Digest, OAuth, and custom schemes.

When using the Parameters property, the values are stored as key-value pairs. The keys are typically parameter names (e.g., "realm", "nonce") and the values are their corresponding strings.

The Parse and TryParse methods are useful for deserializing authentication header strings received from a server or for processing user input.

Consider the following common authentication schemes:

• Basic: new AuthenticationHeaderValue("Basic", "username:password") (Base64 encoded).
• Bearer: new AuthenticationHeaderValue("Bearer", "your_access_token").
• Digest: Often involves multiple parameters like realm, nonce, etc.

Examples

using System;
using System.Net.Http;
using System.Net.Http.Headers;

public class Example
{
    public static void Main()
    {
        // Basic Authentication: Scheme and encoded credentials
        string encodedCredentials = Convert.ToBase64String(System.Text.Encoding.ASCII.GetBytes("user:password"));
        AuthenticationHeaderValue basicAuth = new AuthenticationHeaderValue("Basic", encodedCredentials);

        Console.WriteLine($"Basic Auth Header: {basicAuth}");
        // Output: Basic Auth Header: Basic dXNlcjpwYXNzd29yZA==

        // Bearer Token Authentication
        string accessToken = "your_secure_access_token_here";
        AuthenticationHeaderValue bearerAuth = new AuthenticationHeaderValue("Bearer", accessToken);

        Console.WriteLine($"Bearer Auth Header: {bearerAuth}");
        // Output: Bearer Auth Header: Bearer your_secure_access_token_here

        // Using with HttpClient
        using (var httpClient = new HttpClient())
        {
            httpClient.DefaultRequestHeaders.Authorization = bearerAuth;
            // Now any requests made by this httpClient will include the Authorization header
            // var response = await httpClient.GetAsync("https://api.example.com/data");
        }
    }
}

using System;
using System.Net.Http.Headers;

public class ParseExample
{
    public static void Main()
    {
        string headerString = "Digest realm=\"testrealm\",nonce=\"dcd98b7102dd2f0e8b9478346826607f\",opaque=\"5ccc069c403ebaf930d4215f1961f701\"";

        AuthenticationHeaderValue authHeader;
        if (AuthenticationHeaderValue.TryParse(headerString, out authHeader))
        {
            Console.WriteLine($"Parsed Scheme: {authHeader.Scheme}");
            // Output: Parsed Scheme: Digest

            Console.WriteLine("Parameters:");
            foreach (var parameter in authHeader.Parameters)
            {
                Console.WriteLine($"  - {parameter.Key}: {parameter.Value}");
            }
            // Output:
            // Parameters:
            //   - realm: testrealm
            //   - nonce: dcd98b7102dd2f0e8b9478346826607f
            //   - opaque: 5ccc069c403ebaf930d4215f1961f701
        }
        else
        {
            Console.WriteLine("Failed to parse the authentication header.");
        }
    }
}