Add ModelContextProtocol.Core package (#428)

src/ModelContextProtocol.Core/McpException.cs

@@ -0,0 +1,73 @@
+namespace ModelContextProtocol;
+
+/// <summary>
+/// Represents an exception that is thrown when an Model Context Protocol (MCP) error occurs.
+/// </summary>
+/// <remarks>
+/// This exception is used to represent failures to do with protocol-level concerns, such as invalid JSON-RPC requests,
+/// invalid parameters, or internal errors. It is not intended to be used for application-level errors.
+/// <see cref="Exception.Message"/> or <see cref="ErrorCode"/> from a <see cref="McpException"/> may be 
+/// propagated to the remote endpoint; sensitive information should not be included. If sensitive details need
+/// to be included, a different exception type should be used.
+/// </remarks>
+public class McpException : Exception
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="McpException"/> class.
+    /// </summary>
+    public McpException()
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="McpException"/> class with a specified error message.
+    /// </summary>
+    /// <param name="message">The message that describes the error.</param>
+    public McpException(string message) : base(message)
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="McpException"/> class with a specified error message and a reference to the inner exception that is the cause of this exception.
+    /// </summary>
+    /// <param name="message">The message that describes the error.</param>
+    /// <param name="innerException">The exception that is the cause of the current exception, or a null reference if no inner exception is specified.</param>
+    public McpException(string message, Exception? innerException) : base(message, innerException)
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="McpException"/> class with a specified error message and JSON-RPC error code.
+    /// </summary>
+    /// <param name="message">The message that describes the error.</param>
+    /// <param name="errorCode">A <see cref="McpErrorCode"/>.</param>
+    public McpException(string message, McpErrorCode errorCode) : this(message, null, errorCode)
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="McpException"/> class with a specified error message, inner exception, and JSON-RPC error code.
+    /// </summary>
+    /// <param name="message">The message that describes the error.</param>
+    /// <param name="innerException">The exception that is the cause of the current exception, or a null reference if no inner exception is specified.</param>
+    /// <param name="errorCode">A <see cref="McpErrorCode"/>.</param>
+    public McpException(string message, Exception? innerException, McpErrorCode errorCode) : base(message, innerException)
+    {
+        ErrorCode = errorCode;
+    }
+
+    /// <summary>
+    /// Gets the error code associated with this exception.
+    /// </summary>
+    /// <remarks>
+    /// This property contains a standard JSON-RPC error code as defined in the MCP specification. Common error codes include:
+    /// <list type="bullet">
+    /// <item><description>-32700: Parse error - Invalid JSON received</description></item>
+    /// <item><description>-32600: Invalid request - The JSON is not a valid Request object</description></item>
+    /// <item><description>-32601: Method not found - The method does not exist or is not available</description></item>
+    /// <item><description>-32602: Invalid params - Invalid method parameters</description></item>
+    /// <item><description>-32603: Internal error - Internal JSON-RPC error</description></item>
+    /// </list>
+    /// </remarks>
+    public McpErrorCode ErrorCode { get; } = McpErrorCode.InternalError;
+}