Add ModelContextProtocol.Core package (#428)
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Stephen Halter
GitHub
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commit
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1 changed files with 239 additions and 94 deletions
215
src/ModelContextProtocol.Core/Client/McpClient.cs
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215
src/ModelContextProtocol.Core/Client/McpClient.cs
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using Microsoft.Extensions.Logging;
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using ModelContextProtocol.Protocol;
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using System.Text.Json;
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namespace ModelContextProtocol.Client;
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/// <inheritdoc/>
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internal sealed partial class McpClient : McpEndpoint, IMcpClient
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{
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private static Implementation DefaultImplementation { get; } = new()
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{
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Name = DefaultAssemblyName.Name ?? nameof(McpClient),
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Version = DefaultAssemblyName.Version?.ToString() ?? "1.0.0",
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};
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private readonly IClientTransport _clientTransport;
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private readonly McpClientOptions _options;
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private ITransport? _sessionTransport;
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private CancellationTokenSource? _connectCts;
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private ServerCapabilities? _serverCapabilities;
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private Implementation? _serverInfo;
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private string? _serverInstructions;
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/// <summary>
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/// Initializes a new instance of the <see cref="McpClient"/> class.
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/// </summary>
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/// <param name="clientTransport">The transport to use for communication with the server.</param>
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/// <param name="options">Options for the client, defining protocol version and capabilities.</param>
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/// <param name="loggerFactory">The logger factory.</param>
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public McpClient(IClientTransport clientTransport, McpClientOptions? options, ILoggerFactory? loggerFactory)
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: base(loggerFactory)
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{
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options ??= new();
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_clientTransport = clientTransport;
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_options = options;
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EndpointName = clientTransport.Name;
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if (options.Capabilities is { } capabilities)
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{
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if (capabilities.NotificationHandlers is { } notificationHandlers)
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{
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NotificationHandlers.RegisterRange(notificationHandlers);
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}
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if (capabilities.Sampling is { } samplingCapability)
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{
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if (samplingCapability.SamplingHandler is not { } samplingHandler)
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{
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throw new InvalidOperationException("Sampling capability was set but it did not provide a handler.");
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}
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RequestHandlers.Set(
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RequestMethods.SamplingCreateMessage,
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(request, _, cancellationToken) => samplingHandler(
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request,
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request?.Meta?.ProgressToken is { } token ? new TokenProgress(this, token) : NullProgress.Instance,
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cancellationToken),
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McpJsonUtilities.JsonContext.Default.CreateMessageRequestParams,
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McpJsonUtilities.JsonContext.Default.CreateMessageResult);
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}
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if (capabilities.Roots is { } rootsCapability)
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{
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if (rootsCapability.RootsHandler is not { } rootsHandler)
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{
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throw new InvalidOperationException("Roots capability was set but it did not provide a handler.");
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}
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RequestHandlers.Set(
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RequestMethods.RootsList,
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(request, _, cancellationToken) => rootsHandler(request, cancellationToken),
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McpJsonUtilities.JsonContext.Default.ListRootsRequestParams,
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McpJsonUtilities.JsonContext.Default.ListRootsResult);
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}
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if (capabilities.Elicitation is { } elicitationCapability)
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{
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if (elicitationCapability.ElicitationHandler is not { } elicitationHandler)
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{
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throw new InvalidOperationException("Elicitation capability was set but it did not provide a handler.");
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}
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RequestHandlers.Set(
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RequestMethods.ElicitationCreate,
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(request, _, cancellationToken) => elicitationHandler(request, cancellationToken),
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McpJsonUtilities.JsonContext.Default.ElicitRequestParams,
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McpJsonUtilities.JsonContext.Default.ElicitResult);
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}
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}
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}
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/// <inheritdoc/>
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public ServerCapabilities ServerCapabilities => _serverCapabilities ?? throw new InvalidOperationException("The client is not connected.");
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/// <inheritdoc/>
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public Implementation ServerInfo => _serverInfo ?? throw new InvalidOperationException("The client is not connected.");
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/// <inheritdoc/>
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public string? ServerInstructions => _serverInstructions;
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/// <inheritdoc/>
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public override string EndpointName { get; }
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/// <summary>
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/// Asynchronously connects to an MCP server, establishes the transport connection, and completes the initialization handshake.
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/// </summary>
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public async Task ConnectAsync(CancellationToken cancellationToken = default)
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{
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_connectCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
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cancellationToken = _connectCts.Token;
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try
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{
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// Connect transport
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_sessionTransport = await _clientTransport.ConnectAsync(cancellationToken).ConfigureAwait(false);
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InitializeSession(_sessionTransport);
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// We don't want the ConnectAsync token to cancel the session after we've successfully connected.
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// The base class handles cleaning up the session in DisposeAsync without our help.
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StartSession(_sessionTransport, fullSessionCancellationToken: CancellationToken.None);
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// Perform initialization sequence
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using var initializationCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
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initializationCts.CancelAfter(_options.InitializationTimeout);
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try
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{
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// Send initialize request
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var initializeResponse = await this.SendRequestAsync(
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RequestMethods.Initialize,
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new InitializeRequestParams
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{
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ProtocolVersion = _options.ProtocolVersion,
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Capabilities = _options.Capabilities ?? new ClientCapabilities(),
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ClientInfo = _options.ClientInfo ?? DefaultImplementation,
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},
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McpJsonUtilities.JsonContext.Default.InitializeRequestParams,
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McpJsonUtilities.JsonContext.Default.InitializeResult,
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cancellationToken: initializationCts.Token).ConfigureAwait(false);
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// Store server information
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if (_logger.IsEnabled(LogLevel.Information))
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{
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LogServerCapabilitiesReceived(EndpointName,
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capabilities: JsonSerializer.Serialize(initializeResponse.Capabilities, McpJsonUtilities.JsonContext.Default.ServerCapabilities),
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serverInfo: JsonSerializer.Serialize(initializeResponse.ServerInfo, McpJsonUtilities.JsonContext.Default.Implementation));
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}
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_serverCapabilities = initializeResponse.Capabilities;
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_serverInfo = initializeResponse.ServerInfo;
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_serverInstructions = initializeResponse.Instructions;
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// Validate protocol version
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if (initializeResponse.ProtocolVersion != _options.ProtocolVersion)
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{
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LogServerProtocolVersionMismatch(EndpointName, _options.ProtocolVersion, initializeResponse.ProtocolVersion);
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throw new McpException($"Server protocol version mismatch. Expected {_options.ProtocolVersion}, got {initializeResponse.ProtocolVersion}");
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}
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// Send initialized notification
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await SendMessageAsync(
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new JsonRpcNotification { Method = NotificationMethods.InitializedNotification },
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initializationCts.Token).ConfigureAwait(false);
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}
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catch (OperationCanceledException oce) when (initializationCts.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
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{
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LogClientInitializationTimeout(EndpointName);
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throw new TimeoutException("Initialization timed out", oce);
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}
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}
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catch (Exception e)
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{
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LogClientInitializationError(EndpointName, e);
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await DisposeAsync().ConfigureAwait(false);
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throw;
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}
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}
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/// <inheritdoc/>
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public override async ValueTask DisposeUnsynchronizedAsync()
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{
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try
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{
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if (_connectCts is not null)
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{
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await _connectCts.CancelAsync().ConfigureAwait(false);
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_connectCts.Dispose();
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}
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await base.DisposeUnsynchronizedAsync().ConfigureAwait(false);
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}
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finally
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{
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if (_sessionTransport is not null)
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{
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await _sessionTransport.DisposeAsync().ConfigureAwait(false);
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}
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}
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}
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[LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} client received server '{ServerInfo}' capabilities: '{Capabilities}'.")]
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private partial void LogServerCapabilitiesReceived(string endpointName, string capabilities, string serverInfo);
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[LoggerMessage(Level = LogLevel.Error, Message = "{EndpointName} client initialization error.")]
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private partial void LogClientInitializationError(string endpointName, Exception exception);
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[LoggerMessage(Level = LogLevel.Error, Message = "{EndpointName} client initialization timed out.")]
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private partial void LogClientInitializationTimeout(string endpointName);
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[LoggerMessage(Level = LogLevel.Error, Message = "{EndpointName} client protocol version mismatch with server. Expected '{Expected}', received '{Received}'.")]
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private partial void LogServerProtocolVersionMismatch(string endpointName, string expected, string received);
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}
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