C# method to lock SQL Server table

Question

I have a C# program that needs to perform a group of mass updates (20k+) to a SQL Server table. Since other users can update these records one at a time via an intranet website,

Answer 1

It's all about Isolation level here. Change your Transaction Isolation Level to ReadCommited (didn't lookup the Enum Value in C# but that should be close). When you execute the first update/insert to the table, SQL will start locking and no one will be able to read the data you're changing/adding until you Commit or Rollback thr transaction, provided they are not performing dirty reads (using NoLock on their SQL, or have the connection Isolation level set to Read Uncommited).. Be careful though, depending on how you're inserting/updating data you may lock the whole table for the duration of your transaction though which would cause timeout errors at the client when they try to read from this table while your transaction is open. Without seeing the SQL behind the updates though I can't tell if that will happen here.