Does TRUNCATE TABLE affects isolation level in Sql Server? As I am working on the project which has SQL SERVER  as a database....I'm maintaining isolation level in my project where I enabled snapshot isolation level for my project....

As I have to make some dirty read, I am querying it with setting SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED..I've implemented it in stored proc...Here is short version of my stored proc

ALTER PROCEDURE [dbo].[proc_ReadDirtyData]
@id INT,
@mode VARCHAR(5)

AS
BEGIN
    --Read Dirty Data
    IF (@mode = 'RDD')
    BEGIN
            SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
            SELECT * FROM tbl_transaction
            WHERE id = @id;--@id foreign key in tbl_transaction.
                           --This read has been done during the transaction from C# Apps
    END
END


In my C# apps, following structure is maintained

snapshot transaction start

stage1 : tblmaster --generates id
stage2 :tblchild --inserts the data with above id as foreign key.After successfull inserting,
          --dirty read goes here applying where equal to above id for other operation

if(operationSuccessful)
{
     transactionCommit()
}
else
{
     transactionRollback();
}

snapshot transaction end


I am getting problem in stage2 after TRUNCATE operation on operated table... 

I've been checking whether it makes correct dirty reads,so I used to clear the data of that specific table where dirty read has been occured...

But, the problem comes when I use TRUNCATE for clearing the table data....If I use TRUNCATE, I can't make dirty reads where as if I use DELETE, it perfectly works for dirty read....

Here, I want to make clear that I'm not making dirty read during TRUNCATE/DELETE operation...After TRUNCATE/DELETE operation only, I go for dirty read of fresh data......

Now, I'm curious that whether TRUNCATE affects internal isolation of that table or not....
TRUNCATE table will take a SCH-M lock on the table.

Even at READ UNCOMMITTED level the SELECT query will need to take a SCH-S lock. This won't be possible until the TRUNCATE transaction has ended and the  conflicting SCH-M lock has been released.