mcs/class/referencesource/System.Data.Entity/System/Data/Objects/DataClasses/RelationshipNavigation.cs

   1 //---------------------------------------------------------------------
   2 // <copyright file="RelationshipNavigation.cs" company="Microsoft">
   3 //      Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 //
   6 // @owner       Microsoft
   7 // @backupOwner Microsoft
   8 //---------------------------------------------------------------------
   9
  10 using System;
  11 using System.Collections.Generic;
  12 using System.Data.Common;
  13 using System.Globalization;
  14 using System.Text;
  15 using System.Data.Metadata.Edm;
  16
  17 namespace System.Data.Objects.DataClasses
  18 {
  19     /// <summary>
  20     /// This class describes a relationship navigation from the
  21     /// navigation property on one entity to another entity.  It is
  22     /// used throughout the collections and refs system to describe a
  23     /// relationship and to connect from the navigation property on
  24     /// one end of a relationship to the navigation property on the
  25     /// other end.
  26     /// </summary>
  27     [Serializable]
  28     internal class RelationshipNavigation
  29     {
  30         // ------------
  31         // Constructors
  32         // ------------
  33
  34         /// <summary>
  35         /// Creates a navigation object with the given relationship
  36         /// name, role name for the source and role name for the
  37         /// destination.
  38         /// </summary>
  39         /// <param name="relationshipName">Canonical-space name of the relationship.</param>
  40         /// <param name="from">Name of the role which is the source of the navigation.</param>
  41         /// <param name="to">Name of the role which is the destination of the navigation.</param>
  42         /// <param name="fromAccessor">The navigation property which is the source of the navigation.</param>
  43         /// <param name="toAccessor">The navigation property which is the destination of the navigation.</param>
  44         internal RelationshipNavigation(string relationshipName, string from, string to, NavigationPropertyAccessor fromAccessor, NavigationPropertyAccessor toAccessor)
  45         {
  46             EntityUtil.CheckStringArgument(relationshipName, "relationshipName");
  47             EntityUtil.CheckStringArgument(from, "from");
  48             EntityUtil.CheckStringArgument(to, "to");
  49
  50             _relationshipName = relationshipName;
  51             _from = from;
  52             _to = to;
  53
  54             _fromAccessor = fromAccessor;
  55             _toAccessor = toAccessor;
  56         }
  57
  58         // ------
  59         // Fields
  60         // ------
  61
  62         // The following fields are serialized.  Adding or removing a serialized field is considered
  63         // a breaking change.  This includes changing the field type or field name of existing
  64         // serialized fields. If you need to make this kind of change, it may be possible, but it
  65         // will require some custom serialization/deserialization code.
  66         private readonly string _relationshipName;
  67         private readonly string _from;
  68         private readonly string _to;
  69
  70         [NonSerialized]
  71         private RelationshipNavigation _reverse;
  72
  73         [NonSerialized]
  74         private NavigationPropertyAccessor _fromAccessor;
  75
  76         [NonSerialized]
  77         private NavigationPropertyAccessor _toAccessor;
  78
  79         // ----------
  80         // Properties
  81         // ----------
  82
  83         /// <summary>
  84         /// Canonical-space relationship name.
  85         /// </summary>
  86         internal string RelationshipName
  87         {
  88             get
  89             {
  90                 return _relationshipName;
  91             }
  92         }
  93
  94         /// <summary>
  95         /// Role name for the source of this navigation.
  96         /// </summary>
  97         internal string From
  98         {
  99             get
 100             {
 101                 return _from;
 102             }
 103         }
 104
 105         /// <summary>
 106         /// Role name for the destination of this navigation.
 107         /// </summary>
 108         internal string To
 109         {
 110             get
 111             {
 112                 return _to;
 113             }
 114         }
 115
 116         /// <summary>
 117         /// Navigation property name for the destination of this navigation.
 118         /// NOTE: There is not a FromPropertyAccessor property on RelationshipNavigation because it is not currently accessed anywhere
 119         ///       It is only used to calculate the "reverse" RelationshipNavigation.
 120         /// </summary>
 121         internal NavigationPropertyAccessor ToPropertyAccessor
 122         {
 123             get { return _toAccessor; }
 124         }
 125
 126         internal bool IsInitialized
 127         {
 128             get { return _toAccessor != null && _fromAccessor != null; }
 129         }
 130
 131         internal void InitializeAccessors(NavigationPropertyAccessor fromAccessor, NavigationPropertyAccessor toAccessor)
 132         {
 133             _fromAccessor = fromAccessor;
 134             _toAccessor = toAccessor;
 135         }
 136
 137         /// <summary>
 138         /// The "reverse" version of this navigation.
 139         /// </summary>
 140         internal RelationshipNavigation Reverse
 141         {
 142             get
 143             {
 144                 if (_reverse == null || !_reverse.IsInitialized)
 145                 {
 146                     // the reverse relationship is exactly like this
 147                     // one but from & to are switched
 148                     _reverse = new RelationshipNavigation(_relationshipName, _to, _from, _toAccessor, _fromAccessor);
 149                 }
 150
 151                 return _reverse;
 152             }
 153         }
 154
 155         /// <summary>
 156         /// Compares this instance to a given Navigation by their values.
 157         /// </summary>
 158         public override bool Equals(object obj)
 159         {
 160                 RelationshipNavigation compareTo = obj as RelationshipNavigation;
 161                 return ((this == compareTo)
 162                         || ((null != this) && (null != compareTo)
 163                             && (this.RelationshipName == compareTo.RelationshipName)
 164                             && (this.From == compareTo.From)
 165                             && (this.To == compareTo.To)));
 166         }
 167
 168         /// <summary>
 169         /// Returns a value-based hash code.
 170         /// </summary>
 171         /// <returns>the hash value of this Navigation</returns>
 172         public override int GetHashCode()
 173         {
 174                 return this.RelationshipName.GetHashCode();
 175         }
 176
 177         // -------
 178         // Methods
 179         // -------
 180
 181         /// <summary>
 182         /// ToString is provided to simplify debugging, etc.
 183         /// </summary>
 184         public override string ToString()
 185         {
 186             return String.Format(CultureInfo.InvariantCulture,
 187                                  "RelationshipNavigation: ({0},{1},{2})",
 188                                  _relationshipName,
 189                                  _from,
 190                                  _to);
 191         }
 192     }
 193 }