NOLOCK with Linq to SQL

Question

Is it possible to get Linq2Sql to emit a NOLOCK in its SQL? And if so, how?

Answer 1

Further to theKing's LinqPad My Extensions addition:

public static IQueryable DumpNoLock(this IQueryable query)
{
    using (var txn = GetNewReadUncommittedScope())
    {
        return query.Dump();
    }   
}

public static System.Transactions.TransactionScope GetNewReadUncommittedScope()
{
    return new System.Transactions.TransactionScope(
        System.Transactions.TransactionScopeOption.RequiresNew,
        new System.Transactions.TransactionOptions
        {
            IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted
        });
}
public static IQueryable DumpNoLock(this IQueryable query, string description)
{
    using (var txn = GetNewReadUncommittedScope())
    {
        return query.Dump(description);
    }   
}

public static List ToListNoLock(this IQueryable query)
{
    using (var txn = GetNewReadUncommittedScope())
    {
        return query.ToList();
    }   
}

public static U NoLock(this IQueryable query, Func,U> expr)
{
    using (var txn = GetNewReadUncommittedScope())
    {
        return expr(query);
    }   
}

The last one means you can do a NOLOCK on any evaluating queries you haven't a NoLock explicitly written for (like I've got for ToListNoLock above). So, for example:

somequery.NoLock((x)=>x.Count()).Dump();

will evaluate the query with NOLOCK.

Note that you have to ensure you're evaluating the query. E.g. .NoLock((x)=>x.Distinct()).Count().Dump() won't do anything usefully different from .Distinct().Count().Dump().