We use LINQ in our ASP .NET application to run database queries and commands. We have been having concurrency issues on updates to tables in which we update the value of a Date field. More specifically, if two users click a button at the exact same time and the code attempts to update a Date field in the database then the built-in optimistic concurrency fails to do its job and one the users throws an exception.
Here’s the weird part, if we go into the DBML and set the field’s time stamp property to true and run the unit tests it works just fine…no explicit locks needed.
We would like to understand this a bit more before implementing this throughout the entire system. Does anyone have some understanding as to why this works?
Without knowing the details of your system I would guess that is because SQL Server DATETIME has a resolution of 3 ms at best, giving a high probability for conflicts. TIMESTAMP is a counter in desquise and cannot conflict.