mcs/class/referencesource/System.Data.Entity/System/Data/Mapping/Update/Internal/Propagator.JoinPropagator.SubstitutingCloneVisitor.cs

   1 //---------------------------------------------------------------------
   2 // <copyright file="Propagator.JoinPropagator.SubstitutingCloneVisitor.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.Collections.Generic;
  11 using System.Data.Common;
  12
  13 namespace System.Data.Mapping.Update.Internal
  14 {
  15     internal partial class Propagator
  16     {
  17         private partial class JoinPropagator
  18         {
  19             /// <summary>
  20             /// Describes the mode of behavior for the <see cref="PlaceholderPopulator"/>.
  21             /// </summary>
  22             private enum PopulateMode
  23             {
  24                 /// <summary>
  25                 /// Produce a null extension record (for outer joins) marked as modified
  26                 /// </summary>
  27                 NullModified,
  28                 /// <summary>
  29                 /// Produce a null extension record (for outer joins) marked as preserve
  30                 /// </summary>
  31                 NullPreserve,
  32                 /// <summary>
  33                 /// Produce a placeholder for a record that is known to exist but whose specific
  34                 /// values are unknown.
  35                 /// </summary>
  36                 Unknown,
  37             }
  38
  39             /// <summary>
  40             /// Fills in a placeholder with join key data (also performs a clone so that the
  41             /// placeholder can be reused).
  42             /// </summary>
  43             /// <remarks>
  44             /// Clones of placeholder nodes are created when either the structure of the node
  45             /// needs to change or the record markup for the node needs to change.
  46             /// </remarks>
  47             private static class PlaceholderPopulator
  48             {
  49                 #region Methods
  50                 /// <summary>
  51                 /// Construct a new placeholder with the shape of the given placeholder. Key values are
  52                 /// injected into the resulting place holder and default values are substituted with
  53                 /// either propagator constants or progagator nulls depending on the mode established
  54                 /// by the <paramref name="mode"/> flag.
  55                 /// </summary>
  56                 /// <remarks>
  57                 /// The key is essentially an array of values. The key map indicates that for a particular
  58                 /// placeholder an expression (keyMap.Keys) corresponds to some ordinal in the key array.
  59                 /// </remarks>
  60                 /// <param name="placeholder">Placeholder to clone</param>
  61                 /// <param name="key">Key to substitute</param>
  62                 /// <param name="placeholderKey">Key elements in the placeholder (ordinally aligned with 'key')</param>
  63                 /// <param name="mode">Mode of operation.</param>
  64                 /// <param name="translator">Translator context.</param>
  65                 /// <returns>Cloned placeholder with key values</returns>
  66                 internal static PropagatorResult Populate(PropagatorResult placeholder, CompositeKey key,
  67                     CompositeKey placeholderKey, PopulateMode mode, UpdateTranslator translator)
  68                 {
  69                     EntityUtil.CheckArgumentNull(placeholder, "placeholder");
  70                     EntityUtil.CheckArgumentNull(key, "key");
  71                     EntityUtil.CheckArgumentNull(placeholderKey, "placeholderKey");
  72                     EntityUtil.CheckArgumentNull(translator, "translator");
  73
  74                     // Figure out which flags to apply to generated elements.
  75                     bool isNull = mode == PopulateMode.NullModified || mode == PopulateMode.NullPreserve;
  76                     bool preserve = mode == PopulateMode.NullPreserve || mode == PopulateMode.Unknown;
  77                     PropagatorFlags flags = PropagatorFlags.NoFlags;
  78                     if (!isNull) { flags |= PropagatorFlags.Unknown; } // only null values are known
  79                     if (preserve) { flags |= PropagatorFlags.Preserve; }
  80
  81                     PropagatorResult result = placeholder.Replace(node =>
  82                         {
  83                             // See if this is a key element
  84                             int keyIndex = -1;
  85                             for (int i = 0; i < placeholderKey.KeyComponents.Length; i++)
  86                             {
  87                                 if (placeholderKey.KeyComponents[i] == node)
  88                                 {
  89                                     keyIndex = i;
  90                                     break;
  91                                 }
  92                             }
  93
  94                             if (keyIndex != -1)
  95                             {
  96                                 // Key value.
  97                                 return key.KeyComponents[keyIndex];
  98                             }
  99                             else
 100                             {
 101                                 // for simple entries, just return using the markup context for this
 102                                 // populator
 103                                 object value = isNull ? null : node.GetSimpleValue();
 104                                 return PropagatorResult.CreateSimpleValue(flags, value);
 105                             }
 106                         });
 107
 108                     return result;
 109                 }
 110                 #endregion
 111             }
 112         }
 113     }
 114 }