我遇到过情况,在'乐观更新'的情况下需要EF只读属性(您不会从数据库加载域对象的当前状态以检查哪些属性真的发生更改。你只需将你的对象设置为Modified,并将它更新到数据库。在这种情况下,你避免了冗余的选择和合并操作)。EF 4.1中的只读属性
你不能写这样的:DataContext.Entry(entity).Property(propertyName).IsModified = false;
,因为'false'值的设置不被支持,你会得到一个异常。 (在EF 4.1中)
我创建了一个简单的结构,用于在存储库中注册只读属性。 因此,您可以轻松修改非读取属性。
您对此有何看法?
public abstract class RepositoryBase<T> where T : class
{
private const string MethodReferenceErrorFormat = "Expression '{0}' refers to a method, not a property.";
private const string FieldReferenceErrorFormat = "Expression '{0}' refers to a field, not a property.";
protected IList<PropertyInfo> _readOnlyProperties;
/// <summary>
/// This method is used to register readonly property for Entity.
/// </summary>
/// <param name="propertyLambda">Entity property as LambdaExpression</param>
protected void RegisterReadOnlyProperty<TProperty>(Expression<Func<T, TProperty>> propertyLambda)
{
Guard.ArgumentNotNull(propertyLambda, "propertyLambda");
var propertyMember = propertyLambda.Body as MemberExpression;
if (propertyMember == null)
{
var exceptionMessage = string.Format(MethodReferenceErrorFormat, propertyLambda);
throw new ArgumentException(exceptionMessage);
}
var propertyInfo = propertyMember.Member as PropertyInfo;
if (propertyInfo == null)
{
var exceptionMessage = string.Format(FieldReferenceErrorFormat, propertyLambda);
throw new ArgumentException(exceptionMessage);
}
_readOnlyProperties.Add(propertyInfo);
}
/// <summary>
/// This method is used to attach domain object to DbContext and mark it as modified to save changes.
/// </summary>
/// <param name="entity">Detached entity</param>
public void SetModified(T entity)
{
Guard.ArgumentNotNull(entity, "entity");
//Mark whole entity as Modified, when collection of readonly properties is empty.
if(_readOnlyProperties.Count == 0)
{
DataContext.Entry(entity).State = EntityState.Modified;
return;
}
//Attach entity to DbContext.
_dbSet.Attach(entity);
//Mark all properties except readonly as Modified.
var allProperties = entity.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
var propertiesForUpdate = allProperties.Except(_readOnlyProperties);
foreach (var propertyInfo in propertiesForUpdate)
{
DataContext.Entry(entity).Property(propertyInfo.Name).IsModified = true;
}
}
谢谢!你的版本看起来不错! – zonder 2011-04-21 21:30:44
当我使用它时,它给了我下面的错误,无法将Lambda表达式转换为Type'Expression> []',因为它不是委托类型 –
2013-05-16 08:01:06