263 lines
16 KiB
C#
263 lines
16 KiB
C#
using Microsoft.Extensions.AI;
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using Microsoft.Extensions.DependencyInjection;
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using ModelContextProtocol.Protocol;
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using System.Reflection;
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namespace ModelContextProtocol.Server;
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/// <summary>
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/// Represents an invocable resource used by Model Context Protocol clients and servers.
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/// </summary>
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/// <remarks>
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/// <para>
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/// <see cref="McpServerResource"/> is an abstract base class that represents an MCP resource for use in the server (as opposed
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/// to <see cref="Resource"/> or <see cref="ResourceTemplate"/>, which provide the protocol representations of a resource). Instances of
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/// <see cref="McpServerResource"/> can be added into a <see cref="IServiceCollection"/> to be picked up automatically when
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/// <see cref="McpServer"/> is used to create an <see cref="McpServer"/>, or added into a <see cref="McpServerPrimitiveCollection{McpServerResource}"/>.
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/// </para>
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/// <para>
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/// Most commonly, <see cref="McpServerResource"/> instances are created using the static <see cref="M:McpServerResource.Create"/> methods.
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/// These methods enable creating an <see cref="McpServerResource"/> for a method, specified via a <see cref="Delegate"/> or
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/// <see cref="MethodInfo"/>, and are what are used implicitly by WithResourcesFromAssembly and
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/// <see cref="M:McpServerBuilderExtensions.WithResources"/>. The <see cref="M:McpServerResource.Create"/> methods
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/// create <see cref="McpServerResource"/> instances capable of working with a large variety of .NET method signatures, automatically handling
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/// how parameters are marshaled into the method from the URI received from the MCP client, and how the return value is marshaled back
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/// into the <see cref="ReadResourceResult"/> that's then serialized and sent back to the client.
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/// </para>
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/// <para>
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/// <see cref="McpServerResource"/> is used to represent both direct resources (for example,"resource://example") and templated
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/// resources (for example,"resource://example/{id}").
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/// </para>
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/// <para>
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/// Read resource requests do not contain separate arguments, only a URI. However, for templated resources, portions of that URI may be considered
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/// as arguments and may be bound to parameters. Further, resource methods may accept parameters that will be bound to arguments based on their type.
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/// <list type="bullet">
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/// <item>
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/// <description>
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/// <see cref="CancellationToken"/> parameters are automatically bound to a <see cref="CancellationToken"/> provided by the
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/// <see cref="McpServer"/> and that respects any <see cref="CancelledNotificationParams"/>s sent by the client for this operation's
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/// <see cref="RequestId"/>.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="IServiceProvider"/> parameters are bound from the <see cref="RequestContext{ReadResourceRequestParams}"/> for this request.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="McpServer"/> parameters are bound directly to the <see cref="McpServer"/> instance associated
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/// with this request's <see cref="RequestContext{ReadResourceRequestParams}"/>. Such parameters may be used to understand
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/// what server is being used to process the request, and to interact with the client issuing the request to that server.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="IProgress{ProgressNotificationValue}"/> parameters accepting <see cref="ProgressNotificationValue"/> values
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/// are bound to an <see cref="IProgress{ProgressNotificationValue}"/> instance manufactured to forward progress notifications
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/// from the resource to the client. If the client included a <see cref="ProgressToken"/> in their request, progress reports issued
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/// to this instance will propagate to the client as <see cref="NotificationMethods.ProgressNotification"/> notifications with
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/// that token. If the client did not include a <see cref="ProgressToken"/>, the instance will ignore any progress reports issued to it.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// When the <see cref="McpServerResource"/> is constructed, it may be passed an <see cref="IServiceProvider"/> via
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/// <see cref="McpServerResourceCreateOptions.Services"/>. Any parameter that can be satisfied by that <see cref="IServiceProvider"/>
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/// according to <see cref="IServiceProviderIsService"/> will be resolved from the <see cref="IServiceProvider"/> provided to the
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/// resource invocation rather than from the argument collection.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// Any parameter attributed with <see cref="FromKeyedServicesAttribute"/> will similarly be resolved from the
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/// <see cref="IServiceProvider"/> provided to the resource invocation rather than from the argument collection.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// All other parameters are bound from the data in the URI.
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/// </description>
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/// </item>
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/// </list>
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/// </para>
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/// <para>
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/// Return values from a method are used to create the <see cref="ReadResourceResult"/> that is sent back to the client:
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/// </para>
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/// <list type="table">
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/// <item>
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/// <term><see cref="ResourceContents"/></term>
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/// <description>Wrapped in a list containing the single <see cref="ResourceContents"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="TextContent"/></term>
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/// <description>Converted to a list containing a single <see cref="TextResourceContents"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="DataContent"/></term>
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/// <description>Converted to a list containing a single <see cref="BlobResourceContents"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="string"/></term>
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/// <description>Converted to a list containing a single <see cref="TextResourceContents"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="IEnumerable{ResourceContents}"/> of <see cref="ResourceContents"/></term>
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/// <description>Returned directly as a list of <see cref="ResourceContents"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="IEnumerable{AIContent}"/> of <see cref="AIContent"/></term>
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/// <description>Converted to a list containing a <see cref="TextResourceContents"/> for each <see cref="TextContentBlock"/> and a <see cref="BlobResourceContents"/> for each <see cref="DataContent"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="IEnumerable{String}"/> of <see cref="string"/></term>
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/// <description>Converted to a list containing a <see cref="TextResourceContents"/>, one for each <see cref="string"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="ReadResourceResult"/></term>
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/// <description>Returned directly without modification.</description>
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/// </item>
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/// </list>
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/// <para>
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/// Other returned types will result in an <see cref="InvalidOperationException"/> being thrown.
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/// </para>
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/// </remarks>
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public abstract class McpServerResource : IMcpServerPrimitive
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{
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/// <summary>Initializes a new instance of the <see cref="McpServerResource"/> class.</summary>
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protected McpServerResource()
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{
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}
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/// <summary>Gets a value that indicates whether this resource is a URI template with parameters as opposed to a direct resource.</summary>
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public bool IsTemplated => ProtocolResourceTemplate.UriTemplate.Contains('{');
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/// <summary>Gets the protocol <see cref="ResourceTemplate"/> type for this instance.</summary>
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/// <remarks>
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/// <para>
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/// The <see cref="ProtocolResourceTemplate"/> property represents the underlying resource template definition as defined in the
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/// Model Context Protocol specification. It contains metadata like the resource templates's URI template, name, and description.
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/// </para>
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/// <para>
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/// Every valid resource URI is a valid resource URI template, and thus this property always returns an instance.
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/// In contrast, the <see cref="ProtocolResource"/> property might return <see langword="null"/> if the resource template
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/// contains a parameter, in which case the resource template URI is not a valid resource URI.
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/// </para>
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/// </remarks>
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public abstract ResourceTemplate ProtocolResourceTemplate { get; }
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/// <summary>Gets the protocol <see cref="Resource"/> type for this instance.</summary>
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/// <remarks>
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/// The ProtocolResourceTemplate property represents the underlying resource template definition as defined in the
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/// Model Context Protocol specification. It contains metadata like the resource templates's URI template, name, and description.
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/// </remarks>
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public virtual Resource? ProtocolResource => ProtocolResourceTemplate.AsResource();
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/// <summary>
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/// Gets the metadata for this resource instance.
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/// </summary>
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/// <remarks>
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/// Contains attributes from the associated MethodInfo and declaring class (if any),
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/// with class-level attributes appearing before method-level attributes.
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/// </remarks>
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public abstract IReadOnlyList<object> Metadata { get; }
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/// <summary>
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/// Evaluates whether the <paramref name="uri"/> matches the <see cref="ProtocolResourceTemplate"/>
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/// and can be used as the <see cref="ReadResourceRequestParams.Uri"/> passed to <see cref="ReadAsync"/>.
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/// </summary>
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/// <param name="uri">The URI being evaluated for this resource.</param>
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/// <returns>
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/// <see langword="true"/> if the <paramref name="uri"/> matches the <see cref="ProtocolResourceTemplate"/>; otherwise, <see langword="false"/>.
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/// </returns>
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public abstract bool IsMatch(string uri);
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/// <summary>
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/// Gets the resource, rendering it with the provided request parameters and returning the resource result.
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/// </summary>
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/// <param name="request">
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/// The request context containing information about the resource invocation, including any arguments
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/// passed to the resource. This object provides access to both the request parameters and the server context.
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/// </param>
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/// <param name="cancellationToken">
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/// The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.
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/// </param>
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/// <returns>
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/// A <see cref="ValueTask{ReadResourceResult}"/> representing the asynchronous operation, containing a <see cref="ReadResourceResult"/> with
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/// the resource content and messages.
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/// </returns>
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/// <exception cref="ArgumentNullException"><paramref name="request"/> is <see langword="null"/>.</exception>
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/// <exception cref="InvalidOperationException">
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/// The <see cref="ReadResourceRequestParams.Uri"/> did not match the <see cref="ProtocolResourceTemplate"/> for this resource,
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/// the resource implementation returned <see langword="null"/>, or the resource implementation returned an unsupported result type.
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/// </exception>
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public abstract ValueTask<ReadResourceResult> ReadAsync(
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RequestContext<ReadResourceRequestParams> request,
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CancellationToken cancellationToken = default);
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/// <summary>
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/// Creates an <see cref="McpServerResource"/> instance for a method, specified via a <see cref="Delegate"/> instance.
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/// </summary>
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/// <param name="method">The method to be represented via the created <see cref="McpServerResource"/>.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerResource"/> to control its behavior.</param>
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/// <returns>The created <see cref="McpServerResource"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> is <see langword="null"/>.</exception>
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public static McpServerResource Create(
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Delegate method,
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McpServerResourceCreateOptions? options = null) =>
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AIFunctionMcpServerResource.Create(method, options);
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/// <summary>
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/// Creates an <see cref="McpServerResource"/> instance for a method, specified via a <see cref="Delegate"/> instance.
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/// </summary>
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/// <param name="method">The method to be represented via the created <see cref="McpServerResource"/>.</param>
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/// <param name="target">The instance if <paramref name="method"/> is an instance method; otherwise, <see langword="null"/>.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerResource"/> to control its behavior.</param>
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/// <returns>The created <see cref="McpServerResource"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> is <see langword="null"/>.</exception>
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/// <exception cref="ArgumentException"><paramref name="method"/> is an instance method but <paramref name="target"/> is <see langword="null"/>.</exception>
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public static McpServerResource Create(
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MethodInfo method,
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object? target = null,
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McpServerResourceCreateOptions? options = null) =>
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AIFunctionMcpServerResource.Create(method, target, options);
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/// <summary>
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/// Creates an <see cref="McpServerResource"/> instance for a method, specified via an <see cref="MethodInfo"/> for
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/// an instance method, along with a <see cref="Type"/> representing the type of the target object to
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/// instantiate each time the method is invoked.
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/// </summary>
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/// <param name="method">The instance method to be represented via the created <see cref="AIFunction"/>.</param>
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/// <param name="createTargetFunc">
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/// The callback used on each function invocation to create an instance of the type on which the instance method <paramref name="method"/>
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/// will be invoked. If the returned instance is <see cref="IAsyncDisposable"/> or <see cref="IDisposable"/>, it will
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/// be disposed of after method completes its invocation.
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/// </param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerResource"/> to control its behavior.</param>
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/// <returns>The created <see cref="AIFunction"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> is <see langword="null"/>.</exception>
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public static McpServerResource Create(
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MethodInfo method,
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Func<RequestContext<ReadResourceRequestParams>, object> createTargetFunc,
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McpServerResourceCreateOptions? options = null) =>
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AIFunctionMcpServerResource.Create(method, createTargetFunc, options);
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/// <summary>Creates an <see cref="McpServerResource"/> that wraps the specified <see cref="AIFunction"/>.</summary>
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/// <param name="function">The function to wrap.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerResource"/> to control its behavior.</param>
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/// <exception cref="ArgumentNullException"><paramref name="function"/> is <see langword="null"/>.</exception>
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/// <remarks>
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/// Unlike the other overloads of Create, the <see cref="McpServerResource"/> created by <see cref="Create(AIFunction, McpServerResourceCreateOptions)"/>
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/// does not provide all of the special parameter handling for MCP-specific concepts, like <see cref="McpServer"/>.
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/// </remarks>
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public static McpServerResource Create(
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AIFunction function,
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McpServerResourceCreateOptions? options = null) =>
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AIFunctionMcpServerResource.Create(function, options);
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/// <inheritdoc />
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public override string ToString() => ProtocolResourceTemplate.UriTemplate;
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/// <inheritdoc />
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string IMcpServerPrimitive.Id => ProtocolResourceTemplate.UriTemplate;
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}
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