HttpLibHeaderValue

Represents a header value that can be converted to and from a string.

This is a fundamental type for handling HTTP headers within the System.Net.Http namespace, providing a standardized way to parse and format header values.

Namespace

System.Net.Http.Headers

Class Declaration

public abstract class HttpLibHeaderValue

Introduction

The HttpLibHeaderValue class serves as an abstract base class for types that represent HTTP header values. It defines the essential contract for parsing header values from strings and formatting them back into strings.

Key Concepts

Parsing: Implementations of HttpLibHeaderValue must provide logic to parse a string representation of a header value into a structured object.
Formatting: They must also be able to format the object back into its string representation.
Extensibility: This abstract class allows for the creation of custom header value parsers and formatters for specific HTTP headers.

Common Implementations

Several concrete classes inherit from HttpLibHeaderValue to handle common HTTP header types:

HttpHeaderValue (A generic base for typed header values)
MediaTypeHeaderValue (For Content-Type headers)
RangeUnitHeaderValue (For Range headers)
TransferCodingHeaderValue (For Transfer-Encoding headers)

Abstract Members

Subclasses must implement the following members:

`public abstract bool TryParse(string value, out HttpLibHeaderValue result);`

public abstract bool TryParse(string value, out HttpLibHeaderValue result)

Attempts to parse a string representation of a header value into an instance of a derived class.

Parameters

value: The string to parse.
result: When this method returns, contains the parsed header value if the parsing succeeded, or null if the parsing failed.

Returns

true if the string was parsed successfully; otherwise, false.

`public abstract string ToString();`

public abstract string ToString()

Converts the header value object back into its string representation.

Returns

The string representation of the header value.

Example Usage

Parsing a Content-Type header:


using System.Net.Http.Headers;

string contentTypeString = "application/json; charset=utf-8";
HttpLibHeaderValue parsedValue;

if (MediaTypeHeaderValue.TryParse(contentTypeString, out parsedValue))
{
    MediaTypeHeaderValue mediaType = (MediaTypeHeaderValue)parsedValue;
    Console.WriteLine($"Media Type: {mediaType.MediaType}"); // Output: application/json
    Console.WriteLine($"Char Set: {mediaType.CharSet}");     // Output: utf-8
    Console.WriteLine($"Formatted: {mediaType.ToString()}");  // Output: application/json; charset=utf-8
}
else
{
    Console.WriteLine("Failed to parse Content-Type header.");
}

Creating and formatting a header value:


using System.Net.Http.Headers;

var customHeader = new StringWithQualityHeaderValue("gzip");
string headerString = customHeader.ToString();
Console.WriteLine($"Custom Header: {headerString}"); // Output: gzip

Related Types

HttpLibHeaderValue: The abstract base class.
HttpHeaderValue: A generic base for typed header values, offering more robust parsing and validation.
MediaTypeHeaderValue: Represents Content-Type and Accept header values.
RangeUnitHeaderValue: Represents the unit for Range headers.
TransferCodingHeaderValue: Represents values for the Transfer-Encoding header.
StringWithQualityHeaderValue: Represents header values that include a quality factor, like Accept-Encoding.

`HttpHeaderValue<T>`

public abstract class HttpHeaderValue<T> : HttpLibHeaderValue where T : HttpLibHeaderValue, new()

A generic abstract base class for typed header values. It simplifies the implementation of TryParse by providing a default mechanism to create new instances.

`MediaTypeHeaderValue`

public sealed class MediaTypeHeaderValue : HttpHeaderValue<MediaTypeHeaderValue>

Represents a media type header value, such as "text/html; charset=utf-8". Used for Content-Type and Accept headers.

Members

string MediaType: Gets or sets the media type (e.g., "text/html").
string CharSet: Gets or sets the character set (e.g., "utf-8").
NameValueCollection Parameters: Gets the collection of parameters associated with the media type.
static bool TryParse(string value, out MediaTypeHeaderValue parsedValue): Attempts to parse a string into a MediaTypeHeaderValue.

`RangeUnitHeaderValue`

public sealed class RangeUnitHeaderValue : HttpLibHeaderValue

Represents the unit used in a Range header, such as "bytes".

Members

string Unit: Gets the unit name (e.g., "bytes").
static bool TryParse(string value, out RangeUnitHeaderValue parsedValue): Attempts to parse a string into a RangeUnitHeaderValue.

`TransferCodingHeaderValue`

public abstract class TransferCodingHeaderValue : HttpLibHeaderValue

Abstract base class for transfer coding header values.

Example Implementations

TransferCodingWithQualityHeaderValue