Configure the isolation level to allow ReadUncommited while updating data

Question

I begin a transaction with SqlConnection.BeginTransaction() and I do a DELETE and some INSERTs. There is any configuration I can do on the isolation level to allow any query to read the data on a "dirty way" during the transaction?

Basically I want to prevent locks while I update the data. The problem is; I can't control the SELECTs. If I define a ReadUncommited isolation level on my transaction will the external querys have rights to read the data without waiting or is required to define it on this querys?

For example:

try
{                         
   connection.Open();
   transaction=connection.BeginTransaction(IsolationLevel.ReadUncommited);            

   // DELETE
   foreach (int i in fibarray)
   {
       // INSERTS
   }
   transaction.Commit();
}
catch (Exception ex)
{
   if (transaction.Connection != null)
       transaction.Rollback();
}             

Meanwhile, the SELECTS on another machine I have not the access.

Answer 1

Each connection/session establishes for itself what level of dirtiness it's willing to put up with. There's no way for a different connection to suddenly force a connection to see dirtier data (or, conversely, to be more strict)

The SELECTs have all of the control over their own locking/blocking behaviour. And UPDATEs always have to apply some exclusive locks to complete successfully. So if you cannot change the SELECTs, then you can't overcome your current situation.

Answer 2

Try WITH(NOLOCK) clause on the other SELECTS. This clause will read dirty data.

Example

SELECT ....
FROM <tablename> WITH(NOLOCK) 
WHERE ......

More info here

EDIT: BTW, setting the isolation level ReadUncommited will make the current transaction read uncommitted data, it doesn't control the isolation level of transactions of of the current scope.