I have the following code:
protected static void InsertOrUpdate<T>(
IDbConnection connection,
T item,
Expression<Func<T, bool>> singleItemPredicate,
Expression<Func<T, object>> updateOnlyFields = null)
{
var type = item.GetType();
var idProperty = type.GetProperty("Id");
var currentId = (int)idProperty.GetValue(item);
if (currentId != 0)
{
throw new ApplicationException("Cannot insert or update with non-zero ID");
}
var existingItem = connection.Select(singleItemPredicate).SingleOrDefault();
if (existingItem == null)
{
Insert(connection, item);
return;
}
var existingId = (int)idProperty.GetValue(existingItem);
idProperty.SetValue(item, existingId);
var affectedRowCount = connection.UpdateOnly(item, onlyFields: updateOnlyFields, where: singleItemPredicate);
if (affectedRowCount != 1)
{
throw new ApplicationException("Update failed");
}
}
But using default isolation level, this may produce errors with multiple threads working on the same table.
What I would like is the select-row
to specify that I want an update lock, something like:
var existingItem = connection.Select(singleItemPredicate).WithUpdateLock().SingleOrDefault();
How would I best go about this in ServiceStack OrmLite?
You could use the new SqlExpression SQL Filter just added in v4.5.5 that's now ( available on MyGet ) to customize the generated SQL then execute the custom Typed SqlExpression, eg:
var q = connection.From<T>()
.Where(singleItemPredicate)
.WithSqlFilter(sql => sql + " WITH UPDLOCK");
var existingItem = connection.Select(q).SingleOrDefault();
if (existingItem == null)
{
connection.Insert(item);
return;
}
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