context: //  This file is part of YamlDotNet - A .NET library for YAML.
  //  Copyright (c) Antoine Aubry and contributors
  //  Copyright (c) 2011 Andy Pickett
  
  //  Permission is hereby granted, free of charge, to any person obtaining a copy of
  //  this software and associated documentation files (the "Software"), to deal in
  //  the Software without restriction, including without limitation the rights to
  //  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  //  of the Software, and to permit persons to whom the Software is furnished to do
  //  so, subject to the following conditions:
  
  //  The above copyright notice and this permission notice shall be included in all
  //  copies or substantial portions of the Software.
  
  //  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  //  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  //  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  //  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  //  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  //  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  //  SOFTWARE.
  
  using System;
  using System.Collections.Generic;
  using System.Reflection;
  using System.Text;
  using YamlDotNet.Core;
  using YamlDotNet.Core.Events;
  using YamlDotNet.Serialization;
  
  namespace YamlDotNet.RepresentationModel
  {
      /// <summary>
      /// Represents a mapping node in the YAML document.
      /// </summary>
      [Serializable]
      public sealed class YamlMappingNode : YamlNode, IEnumerable<KeyValuePair<YamlNode, YamlNode>>, IYamlConvertible
      {
          private readonly IDictionary<YamlNode, YamlNode> children = new Dictionary<YamlNode, YamlNode>();
  
          /// <summary>
          /// Gets the children of the current node.
          /// </summary>
          /// <value>The children.</value>
          public IDictionary<YamlNode, YamlNode> Children
          {
              get
              {
                  return children;
              }
          }
  
          /// <summary>
          /// Gets or sets the style of the node.
          /// </summary>
          /// <value>The style.</value>
          public MappingStyle Style { get; set; }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          internal YamlMappingNode(IParser parser, DocumentLoadingState state)
          {
              Load(parser, state);
          }
  
          private void Load(IParser parser, DocumentLoadingState state)
          {
              var mapping = parser.Expect<MappingStart>();
              Load(mapping, state);
              Style = mapping.Style;
  
              bool hasUnresolvedAliases = false;
              while (!parser.Accept<MappingEnd>())
              {
                  var key = ParseNode(parser, state);
                  var value = ParseNode(parser, state);
  
                  try
                  {
                      children.Add(key, value);
                  }
                  catch (ArgumentException err)
                  {
                      throw new YamlException(key.Start, key.End, "Duplicate key", err);
                  }
  
                  hasUnresolvedAliases |= key is YamlAliasNode || value is YamlAliasNode;
              }
  
              if (hasUnresolvedAliases)
              {
                  state.AddNodeWithUnresolvedAliases(this);
              }
  
              parser.Expect<MappingEnd>();
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          public YamlMappingNode()
          {
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          public YamlMappingNode(int dummy) // dummy makes the call to the constructor unambiguous to buggy compilers like mono in Unity.
          {
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          public YamlMappingNode(params KeyValuePair<YamlNode, YamlNode>[] children)
              : this((IEnumerable<KeyValuePair<YamlNode, YamlNode>>)children)
          {
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          public YamlMappingNode(IEnumerable<KeyValuePair<YamlNode, YamlNode>> children)
          {
              foreach (var child in children)
              {
                  this.children.Add(child);
              }
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          /// <param name="children">A sequence of <see cref="YamlNode"/> where even elements are keys and odd elements are values.</param>
          public YamlMappingNode(params YamlNode[] children)
              : this((IEnumerable<YamlNode>)children)
          {
          }
  
          /// <summary>
          /// Initializes a new instance of the <see cref="YamlMappingNode"/> class.
          /// </summary>
          /// <param name="children">A sequence of <see cref="YamlNode"/> where even elements are keys and odd elements are values.</param>
          public YamlMappingNode(IEnumerable<YamlNode> children)
          {
              using (var enumerator = children.GetEnumerator())
              {
                  while (enumerator.MoveNext())
                  {
                      var key = enumerator.Current;
                      if (!enumerator.MoveNext())
                      {
                          throw new ArgumentException("When constructing a mapping node with a sequence, the number of elements of the sequence must be even.");
                      }
  
                      Add(key, enumerator.Current);
                  }
              }
          }
  
          /// <summary>
          /// Adds the specified mapping to the <see cref="Children"/> collection.
          /// </summary>
          /// <param name="key">The key node.</param>
          /// <param name="value">The value node.</param>
          public void Add(YamlNode key, YamlNode value)
          {
              children.Add(key, value);
          }
  
          /// <summary>
          /// Adds the specified mapping to the <see cref="Children"/> collection.
          /// </summary>
          /// <param name="key">The key node.</param>
          /// <param name="value">The value node.</param>
          public void Add(string key, YamlNode value)
          {
              children.Add(new YamlScalarNode(key), value);
          }
  
          /// <summary>
          /// Adds the specified mapping to the <see cref="Children"/> collection.
          /// </summary>
          /// <param name="key">The key node.</param>
          /// <param name="value">The value node.</param>
          public void Add(YamlNode key, string value)
          {
              children.Add(key, new YamlScalarNode(value));
          }
  
          /// <summary>
          /// Adds the specified mapping to the <see cref="Children"/> collection.
          /// </summary>
          /// <param name="key">The key node.</param>
          /// <param name="value">The value node.</param>
          public void Add(string key, string value)
          {
              children.Add(new YamlScalarNode(key), new YamlScalarNode(value));
          }
  
          /// <summary>
          /// Resolves the aliases that could not be resolved when the node was created.
          /// </summary>
          /// <param name="state">The state of the document.</param>
          internal override void ResolveAliases(DocumentLoadingState state)
          {
  
gt:             Dictionary<YamlNode, YamlNode> keysToUpdate = null;