transaction question in SQL Server 2008

Question

I am using SQL Server 2008 Enterprise. And using ADO.Net + C# + .Net 3.5 + ASP.Net as client to access database. When I access SQL Server 2008 tables, I always invoke stored procedure from my C# + ADO.Net code.

My question is, if I do not have any transaction control (I mean begin/end transaction) from my client C# + ADO.Net code, and I also do not have any transaction control (I mean begin/end transaction) in sql stored procedure code. Then my question is, each single Insert/Delete/Update/Select statement will act as a single transaction? Is that correct? For example, in the following store procedure, delete/insert/select will act as 3 single transactions?

create PROCEDURE [dbo].[FooProc]    
(  
 @Param1 int 
 ,@Param2 int  
 ,@Param3 int  
)    
AS    

DELETE FooTable WHERE  Param1 = @Param1     

INSERT INTO FooTable    
 (  
 Param1  
 ,Param2  
 ,Param3  
  )    
 VALUES    
 (  
 @Param1  
 ,@Param2  
 ,@Param3  
  )    

DECLARE @ID bigint    
 SET @ID = ISNULL(@@Identity,-1)    
 IF @ID > 0    
 BEGIN    
      SELECT IdentityStr FROM FooTable WHERE ID = @ID 
 END 

Answer 1

If you don't handle transactions then each statement will be independent and might interfere with other users running the stored procedure at the same time.

Answer 2

Then my question is, each single Insert/Delete/Update/Select statement will act as a single transaction?

Yes, without explicit transaction control, each SQL statement will be wrapped in its own transaction. The single statement is guaranteed to be executed as a whole or fail as a whole.

The single statements will run under the current transaction isolation level: normally read committed. So it won't read uncommitted changes from other statements, but it might suffer from nonrepeatable reads, or phantom values.