我曾经遇到这样的情况,需要在“乐观更新”情况下拥有EF只读属性(您不需要从数据库加载当前状态的域对象来检查哪些属性实际上已更改。您只需将对象设置为已修改,并将其更新到数据库中。在这种情况下,您可以避免冗余的选择和合并操作)。
您不能像这样编写代码:
我创建了一个简单的结构来注册只读属性在存储库中。因此,您可以轻松地修改非只读属性。
您对此有何看法?
您不能像这样编写代码:
DataContext.Entry(entity).Property(propertyName).IsModified = false;
,因为不支持设置“false”值,您会收到异常(在EF 4.1中)。我创建了一个简单的结构来注册只读属性在存储库中。因此,您可以轻松地修改非只读属性。
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;
}
}