Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Objects / Internal / ForeignKeyFactory.cs / 1305376 / ForeignKeyFactory.cs
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using System.Data.Metadata.Edm; using System.Diagnostics; using System.Data.Objects.DataClasses; namespace System.Data.Objects.Internal { internal class ForeignKeyFactory { private const string s_NullPart = "EntityHasNullForeignKey"; private const string s_NullForeignKey = "EntityHasNullForeignKey.EntityHasNullForeignKey"; ////// Returns true if the supplied key represents a Conceptual Null /// /// The key to be checked public static bool IsConceptualNullKey(EntityKey key) { if (key == null) { return false; } return string.Equals(key.EntityContainerName, s_NullPart) && string.Equals(key.EntitySetName, s_NullPart); } ////// Checks if the Real Key represents different FK values /// than those present when the Conceptual Null was created /// /// The key representing the Conceptual Null /// The key to be checked ///True if the values are different, false otherwise public static bool IsConceptualNullKeyChanged(EntityKey conceptualNullKey, EntityKey realKey) { Debug.Assert(IsConceptualNullKey(conceptualNullKey), "The key supplied is not a null key"); if (realKey == null) { return true; } return !EntityKey.InternalEquals(conceptualNullKey, realKey, compareEntitySets: false); } ////// Creates an EntityKey that represents a Conceptual Null /// /// An EntityKey representing the existing FK values that could not be nulled ///EntityKey marked as a conceptual null with the FK values from the original key public static EntityKey CreateConceptualNullKey(EntityKey originalKey) { Debug.Assert(originalKey != null, "Original key can not be null"); //Conceptual nulls have special entity set name and a copy of the previous values EntityKey nullKey = new EntityKey(s_NullForeignKey, originalKey.EntityKeyValues); return nullKey; } ////// Creates an EntityKey for a principal entity based on the foreign key values contained /// in this entity. This implies that this entity is at the dependent end of the relationship. /// /// The EntityEntry for the dependent that contains the FK /// Identifies the principal end for which a key is required ///The key, or null if any value in the key is null public static EntityKey CreateKeyFromForeignKeyValues(EntityEntry dependentEntry, RelatedEnd relatedEnd) { // Note: there is only ever one constraint per association type ReferentialConstraint constraint = ((AssociationType)relatedEnd.RelationMetadata).ReferentialConstraints.First(); Debug.Assert(constraint.FromRole.Identity == relatedEnd.TargetRoleName, "Unexpected constraint role"); return CreateKeyFromForeignKeyValues(dependentEntry, constraint, relatedEnd.GetTargetEntitySetFromRelationshipSet(), useOriginalValues: false); } ////// Creates an EntityKey for a principal entity based on the foreign key values contained /// in this entity. This implies that this entity is at the dependent end of the relationship. /// /// The EntityEntry for the dependent that contains the FK /// The constraint that describes this FK relationship /// The entity set at the principal end of the the relationship /// If true then the key will be constructed from the original FK values ///The key, or null if any value in the key is null public static EntityKey CreateKeyFromForeignKeyValues(EntityEntry dependentEntry, ReferentialConstraint constraint, EntitySet principalEntitySet, bool useOriginalValues) { // Build the key values. If any component of the key is null, then the entire key // is considered null. var dependentProps = constraint.ToProperties; int numValues = dependentProps.Count; if (numValues == 1) { object keyValue = useOriginalValues ? dependentEntry.GetOriginalEntityValue(dependentProps.First().Name) : dependentEntry.GetCurrentEntityValue(dependentProps.First().Name); return keyValue == DBNull.Value ? null : new EntityKey(principalEntitySet, keyValue); } // Note that the properties in the principal entity set may be in a different order than // they appear in the constraint. Therefore, we create name value mappings to ensure that // the correct values are associated with the correct properties. // Unfortunately, there is not way to call the public EntityKey constructor that takes pairs // because the internal "object" constructor hides it. Even this doesn't work: // new EntityKey(principalEntitySet, (IEnumerable>)keyValues) string[] keyNames = principalEntitySet.ElementType.KeyMemberNames; Debug.Assert(keyNames.Length == numValues, "Number of entity set key names does not match constraint names"); object[] values = new object[numValues]; var principalProps = constraint.FromProperties; for (int i = 0; i < numValues; i++) { object value = useOriginalValues ? dependentEntry.GetOriginalEntityValue(dependentProps[i].Name) : dependentEntry.GetCurrentEntityValue(dependentProps[i].Name); if (value == DBNull.Value) { return null; } int keyIndex = Array.IndexOf(keyNames, principalProps[i].Name); Debug.Assert(keyIndex >= 0 && keyIndex < numValues, "Could not find constraint prop name in entity set key names"); values[keyIndex] = value; } return new EntityKey(principalEntitySet, values); } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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