VB Interview Questions

1. How do you register a component? Expected answer: Compiling the component, running REGSVR32 MyDLL.dll

2. Name and explain the different compatibility types when creating a COM component. Expected answer: No Compatibility ? New GUID created, references from other components will not workProject Compatibility ? Default for a new component Binary Compatibility ? GUID does not change, references from other components will work

3. Why iss it important to use source control software for source code? Expected answer: Modification history.Code ownership: Multiple people can not modify the same code at the same time.

4. What two methods are called from the ObjectContext object to inform MTS that the transaction was successful or unsuccessful? Expected answer: SetComplete and SetAbort.

5. What is the tool used to configure the port range and protocols for DCOM communications? Expected answer: DCOMCONFIG.EXE

6. What does Option Explicit refer to? Expected answer: All variables must be declared before use. Their type is not required.

7. What are the different ways to Declare and Instantiate an object in Visual Basic 6? Expected answer: Dim obj as OBJ.CLASS with eitherSet obj = New OBJ.CLASS orSet obj = CreateObject(?OBJ.CLASS?) orSet obj = GetObject( ,? OBJ.CLASS?)orDim obj as New OBJ.CLASS

8. Name the four different cursor types in ADO and describe them briefly. Expected answer: The cursor types are listed from least to most resource intensive.Forward Only ? Fastest, can only move forward in recordset Static ? Can move to any record in the recordset. Data is static and never changes.KeySet ? Changes are detectable, records that are deleted by other users are unavailable, and records created by other users are not detectedDynamic ? All changes are visible.

9. Name the four different locking type in ADO and describe them briefly. Expected answer: LockPessimistic ? Locks the row once after any edits occur.LockOptimistic ? Locks the row only when Update is called.LockBatchOptimistic ? Allows Batch Updates.LockReadOnly ? Read only. Can not alter the data.

10. Describe Database Connection pooling (relative to MTS ) Expected answer: This allows MTS to reuse database connections. Database connections are put to ?sleep? as opposed to being created and destroyed and are activated upon request.

11. What are the ADO objects? Explain them. Provide a scenario using three of them to return data from a database. Expected answer: Connection ? Connects to a data source; contains the Errors collectionCommand ? Executes commands to the data source. Is the only object that can accept parameters for a stored procedure.Recordset ? The set of data returned from the database.Scenario: There are many possibilities. The most likely is as follows:Dim conn As ADODB.ConnectionDim rs As ADODB.RecordsetDim Cmd As ADODB.Commandconn.ConnectionString = ?CONNECTION STRING?conn.OpenSet Cmd.ActiveConnection = connCmd.CommandText = ?SQL STATEMENT?Set rs = Cmd.ExecuteSet rs.ActiveConnection = Nothingconn.Close

12. Under the ADO Command Object, what collection is responsible for input to stored procedures? Expected answer: The Parameters collection.

13. What are some benefits of using MTS? Expected answer: Database Pooling, Transactional operations, Deployment, Security, Remote Execution.

14. What is the benefit of wrapping database calls into MTS transactions? Expected answer: If database calls are made within the context of a transaction, aborting the transaction will undo and changes that occur within that transaction. This removes the possibility of stranded, or partial data.

15. Describe and In Process vs. Out of Process component. Which is faster? Expected answer:An in-process component is implemented as a DLL, and runs in the same process space as its client app, enabling the most efficient communication between client and component.Each client app that uses the component starts a new instance of it.An out of process component is implemented as an EXE, and unlike a dll, runs in its own process space. As a result, exe’s are slower then dll’s because communications between client and component must be marshalled across process boundaries. A single instance of an out of process component can service many clients.

16. What are the main components of the ADO object model? How are they used? Expected answer:Connection: Used to make a connection between your app and an external data source, ie, sql server.Command: Used to build queries, including user-specific parameters, to access records from a data source (which are returned in a Recordset)Recordset:Used to access records returned from an SQL query. With a recordset, you can navigate returned records. You can also add, modify or delete records.