EntityTagHeaderParser Class

System.Net.Http.Headers

Parses the ETag header.

Syntax


public static class EntityTagHeaderParser

Methods

Parse(string value)

Parses an ETag header value.


public static EntityTagHeaderValue Parse(string value)

Parameters

string value: The ETag header value to parse.

Return Value

An instance of EntityTagHeaderValue.

Exceptions

ArgumentNullException: value is null.
FormatException: value is not a valid ETag header value.

TryParse(string value, out EntityTagHeaderValue result)

Tries to parse an ETag header value.


public static bool TryParse(string value, out EntityTagHeaderValue result)

Parameters

string value: The ETag header value to parse.
out EntityTagHeaderValue result: When this method returns, contains the parsed EntityTagHeaderValue.

Return Value

true if value is a valid ETag header value; otherwise, false.

Remarks

The EntityTagHeaderParser class is used internally by the HttpClient and related classes to parse the ETag header, which is used for cache validation.

An ETag header is a unique identifier for a specific version of a resource. It is used in conjunction with the If-None-Match request header to determine if a cached version of a resource is still current.

Example

The following code shows how to parse an ETag header value:

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

public class Example
{
    public static void Main()
    {
        string etagValue = "\"abcde\"";
        EntityTagHeaderValue etag;

        if (EntityTagHeaderParser.TryParse(etagValue, out etag))
        {
            Console.WriteLine($"Successfully parsed ETag: {etag.Tag}");
            Console.WriteLine($"IsStrong: {etag.IsStrong}");
        }
        else
        {
            Console.WriteLine("Failed to parse ETag.");
        }

        string invalidEtagValue = "invalid-etag";
        if (!EntityTagHeaderParser.TryParse(invalidEtagValue, out etag))
        {
            Console.WriteLine($"Correctly identified invalid ETag: {invalidEtagValue}");
        }
    }
}
                
            