- How do you register a component? Expected answer: Compiling the component, running REGSVR32 MyDLL.dll
- 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 - 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.
- What two methods are called from the ObjectContext object to inform MTS that the transaction was successful or unsuccessful? Expected answer: SetComplete and SetAbort.
- What is the tool used to configure the port range and protocols for DCOM communications? Expected answer: DCOMCONFIG.EXE
- What does Option Explicit refer to? Expected answer: All variables must be declared before use. Their type is not required.
- 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
- 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.
- 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.
- 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.
- 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
- Under the ADO Command Object, what collection is responsible for input to stored procedures? Expected answer: The Parameters collection.
- What are some benefits of using MTS? Expected answer: Database Pooling, Transactional operations, Deployment, Security, Remote Execution.
- 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.
- 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.
- 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.
VB Interview Questions
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