本文整理汇总了C#中EntityEntry.GetCurrentEntityValue方法的典型用法代码示例。如果您正苦于以下问题：C# EntityEntry.GetCurrentEntityValue方法的具体用法？C# EntityEntry.GetCurrentEntityValue怎么用？C# EntityEntry.GetCurrentEntityValue使用的例子？那么, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类EntityEntry的用法示例。
在下文中一共展示了EntityEntry.GetCurrentEntityValue方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的C#代码示例。
示例1: CreateKeyFromForeignKeyValues
/// <summary>
/// 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.
/// </summary>
/// <param name="dependentEntry"> The EntityEntry for the dependent that contains the FK </param>
/// <param name="constraint"> The constraint that describes this FK relationship </param>
/// <param name="principalEntitySet"> The entity set at the principal end of the the relationship </param>
/// <param name="useOriginalValues"> If true then the key will be constructed from the original FK values </param>
/// <returns> The key, or null if any value in the key is null </returns>
public static EntityKey CreateKeyFromForeignKeyValues(
EntityEntry dependentEntry, ReferentialConstraint constraint, EntitySet principalEntitySet, bool useOriginalValues)
{
// Build the key values. If any part of the key is null, then the entire key
// is considered null.
var dependentProps = constraint.ToProperties;
var numValues = dependentProps.Count;
if (numValues == 1)
{
var 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<KeyValuePair<string, object>>)keyValues)
var keyNames = principalEntitySet.ElementType.KeyMemberNames;
Debug.Assert(keyNames.Length == numValues, "Number of entity set key names does not match constraint names");
var values = new object[numValues];
var principalProps = constraint.FromProperties;
for (var i = 0; i < numValues; i++)
{
var value = useOriginalValues
? dependentEntry.GetOriginalEntityValue(dependentProps[i].Name)
: dependentEntry.GetCurrentEntityValue(dependentProps[i].Name);
if (value == DBNull.Value)
{
return null;
}
var 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);
}