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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Map / Update / Internal / CompositeKey.cs / 1305376 / CompositeKey.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System.Data.Common.Utils; using System.Collections.Generic; using System.Collections.ObjectModel; using System.Diagnostics; using System.Linq; namespace System.Data.Mapping.Update.Internal { ////// Represents a key composed of multiple parts. /// internal class CompositeKey { #region Fields ////// Gets components of this composite key. /// internal readonly PropagatorResult[] KeyComponents; #endregion #region Constructors ////// Initialize a new composite key using the given constant values. Order is important. /// /// Key values. internal CompositeKey(PropagatorResult[] constants) { Debug.Assert(null != constants, "key values must be given"); KeyComponents = constants; } #endregion #region Methods ////// Creates a key comparer operating in the context of the given translator. /// internal static IEqualityComparerCreateComparer(KeyManager keyManager) { return new CompositeKeyComparer(keyManager); } /// /// Creates a merged key instance where each key component contains both elements. /// /// Must be a non-null compatible key (same number of components). ///Merged key. internal CompositeKey Merge(KeyManager keyManager, CompositeKey other) { Debug.Assert(null != other && other.KeyComponents.Length == this.KeyComponents.Length, "expected a compatible CompositeKey"); PropagatorResult[] mergedKeyValues = new PropagatorResult[this.KeyComponents.Length]; for (int i = 0; i < this.KeyComponents.Length; i++) { mergedKeyValues[i] = this.KeyComponents[i].Merge(keyManager, other.KeyComponents[i]); } return new CompositeKey(mergedKeyValues); } #endregion ////// Equality and comparison implementation for composite keys. /// private class CompositeKeyComparer : IEqualityComparer{ private readonly KeyManager _manager; internal CompositeKeyComparer(KeyManager manager) { _manager = EntityUtil.CheckArgumentNull(manager, "manager"); } // determines equality by comparing each key component public bool Equals(CompositeKey left, CompositeKey right) { // Short circuit the comparison if we know the other reference is equivalent if (object.ReferenceEquals(left, right)) { return true; } // If either side is null, return false order (both can't be null because of // the previous check) if (null == left || null == right) { return false; } Debug.Assert(null != left.KeyComponents && null != right.KeyComponents, "(Update/JoinPropagator) CompositeKey must be initialized"); if (left.KeyComponents.Length != right.KeyComponents.Length) { return false; } for (int i = 0; i < left.KeyComponents.Length; i++) { PropagatorResult leftValue = left.KeyComponents[i]; PropagatorResult rightValue = right.KeyComponents[i]; // if both side are identifiers, check if they're the same or one is constrained by the // other (if there is a dependent-principal relationship, they get fixed up to the same // value) if (leftValue.Identifier != PropagatorResult.NullIdentifier) { if (rightValue.Identifier == PropagatorResult.NullIdentifier || _manager.GetCliqueIdentifier(leftValue.Identifier) != _manager.GetCliqueIdentifier(rightValue.Identifier)) { return false; } } else { if (rightValue.Identifier != PropagatorResult.NullIdentifier || !ByValueEqualityComparer.Default.Equals(leftValue.GetSimpleValue(), rightValue.GetSimpleValue())) { return false; } } } return true; } // creates a hash code by XORing hash codes for all key components. public int GetHashCode(CompositeKey key) { EntityUtil.CheckArgumentNull(key, "key"); int result = 0; foreach (PropagatorResult keyComponent in key.KeyComponents) { result = (result << 5) ^ GetComponentHashCode(keyComponent); } return result; } // Gets the value to use for hash code private int GetComponentHashCode(PropagatorResult keyComponent) { if (keyComponent.Identifier == PropagatorResult.NullIdentifier) { // no identifier exists for this key component, so use the actual key // value Debug.Assert(null != keyComponent && null != keyComponent, "key value must not be null"); return ByValueEqualityComparer.Default.GetHashCode(keyComponent.GetSimpleValue()); } else { // use ID for FK graph clique (this ensures that keys fixed up to the same // value based on a constraint will have the same hash code) return _manager.GetCliqueIdentifier(keyComponent.Identifier).GetHashCode(); } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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