> ## Documentation Index > Fetch the complete documentation index at: https://ai.easyaf.dev/llms.txt > Use this file to discover all available pages before exploring further. # WwwAuthenticateParser > Parses `WWW-Authenticate` response header values into [OAuthChallenge](/odata-mcp/api-reference/Microsoft/OData/Mcp/Authentication/Outbound/OAuthChallenge) instances u... ## Definition **Assembly:** Microsoft.OData.Mcp.Authentication.dll **Namespace:** Microsoft.OData.Mcp.Authentication.Outbound **Inheritance:** System.Object ## Syntax ```csharp theme={null} Microsoft.OData.Mcp.Authentication.Outbound.WwwAuthenticateParser ``` ## Summary Parses `WWW-Authenticate` response header values into [OAuthChallenge](https://ai.easyaf.dev/odata-mcp/api-reference/Microsoft/OData/Mcp/Authentication/Outbound/OAuthChallenge.md) instances using the RFC 9110 section 11.6.1 challenge grammar and the RFC 6750 / RFC 9728 OAuth auth-params. ## Remarks The grammar implemented is `challenge = auth-scheme [ 1*SP ( token68 / #auth-param ) ]` with `auth-param = token BWS "=" BWS ( token / quoted-string )`. A hand written tokenizer is used rather than a regular expression so that a comma inside a quoted-string never splits a challenge, and so that the scheme of a following challenge (a token that is not followed by `=`) is recognized correctly. A `token68` credential is consumed so that it cannot masquerade as an extra challenge, but it is not surfaced: OAuth challenges always use auth-params. ## Methods ### Parse Parses a single `WWW-Authenticate` header value and returns its first challenge. #### Syntax ```csharp theme={null} public static Microsoft.OData.Mcp.Authentication.Outbound.OAuthChallenge Parse(string headerValue) ``` #### Parameters | Name | Type | Description | | - | - | - | | `headerValue` | `string` | The raw header value, for example `Bearer realm="", scope="read"`. | #### Returns Type: `Microsoft.OData.Mcp.Authentication.Outbound.OAuthChallenge` The first [OAuthChallenge](https://ai.easyaf.dev/odata-mcp/api-reference/Microsoft/OData/Mcp/Authentication/Outbound/OAuthChallenge.md) in *headerValue*. #### Exceptions | Exception | Description | | - | - | | `ArgumentNullException` | *headerValue* is [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null). | | `ArgumentException` | *headerValue* is empty or white space. | | `FormatException` | *headerValue* does not contain a well formed challenge. | #### Examples ```csharp theme={null} var challenge = WwwAuthenticateParser.Parse("Bearer realm=\"\", client_id=\"00000003-0000-0000-c000-000000000000\""); Console.WriteLine(challenge.Scheme); // Bearer Console.WriteLine(challenge.Realm); // (empty string) Console.WriteLine(challenge.ResourceClientId); // 00000003-0000-0000-c000-000000000000 ``` #### Remarks Use [String)](https://learn.microsoft.com/dotnet/api/microsoft.odata.mcp.authentication.outbound.wwwauthenticateparser.parseall\(system.string\)) when a header value may advertise more than one scheme; this method deliberately keeps only the first challenge. ### ParseAll Parses a sequence of `WWW-Authenticate` header values, in order, into a flat challenge list. #### Syntax ```csharp theme={null} public static System.Collections.Generic.IReadOnlyList ParseAll(System.Collections.Generic.IEnumerable values) ``` #### Parameters | Name | Type | Description | | - | - | - | | `values` | `System.Collections.Generic.IEnumerable` | The header values, typically the ones surfaced on an OData execute result. | #### Returns Type: `System.Collections.Generic.IReadOnlyList` Every challenge advertised across *values*, in the order encountered. #### Exceptions | Exception | Description | | - | - | | `ArgumentNullException` | *values* is [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null). | | `FormatException` | One of the values is not a well formed challenge. | #### Remarks A response may repeat the header instead of comma joining it, and each value may itself carry more than one challenge. Entries that are [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null), empty, or white space carry no challenge and are skipped, so a response with no usable challenge yields an empty list rather than an exception; callers apply the "401 with no WWW-Authenticate" rule themselves. ### ParseAll Parses a single `WWW-Authenticate` header value that may advertise several challenges. #### Syntax ```csharp theme={null} public static System.Collections.Generic.IReadOnlyList ParseAll(string headerValue) ``` #### Parameters | Name | Type | Description | | - | - | - | | `headerValue` | `string` | The raw header value, for example `Bearer realm="a", Basic realm="b"`. | #### Returns Type: `System.Collections.Generic.IReadOnlyList` Every challenge in *headerValue*, in the order encountered. #### Exceptions | Exception | Description | | - | - | | `ArgumentNullException` | *headerValue* is [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null). | | `ArgumentException` | *headerValue* is empty or white space. | | `FormatException` | *headerValue* is not a well formed challenge list. | ### SelectBearer Selects the first `Bearer` challenge from a parsed challenge list. #### Syntax ```csharp theme={null} public static Microsoft.OData.Mcp.Authentication.Outbound.OAuthChallenge SelectBearer(System.Collections.Generic.IReadOnlyList challenges) ``` #### Parameters | Name | Type | Description | | - | - | - | | `challenges` | `System.Collections.Generic.IReadOnlyList` | The challenges to search, in the order the server advertised them. | #### Returns Type: `Microsoft.OData.Mcp.Authentication.Outbound.OAuthChallenge?` The first challenge whose scheme is `Bearer`, or [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null) when none is. #### Exceptions | Exception | Description | | - | - | | `ArgumentNullException` | *challenges* is [`null`](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null). | #### Remarks Authentication schemes are case-insensitive, so `bearer` and `Bearer` both match. 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