VB.NET

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VB.NET Interview questions and answer part 3.

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By Nishant Kumar 

Part 1 | Part 2 | Part 3 | Part 4 | part 5

Define arrays and collections.  |   Why do you use properties instead of fields?  |   Define delegate.  |   Define parse method.  |   Briefly describe kinds of multidimensional arrays.  |   What is encapsulation?  |   Define method overloading.  |   Describe an abstract class.  |   Describe Break mode.  |    Define Watch window?  |   What is trace? Describe its working.  |   Describe exception handling in VB.NET.  |   What is data provider? Explain its components.  |   ADO.NET.  |   Explain commandType property of a SqlCommand object.  |   Define typed and untyped DataSet objects.   

Question - Define arrays and collections.
Answer - An array is fixed length type that can store group of objects. A collection can also store group of objects. But unlike an array which is fixed length, the collection can grow or shrink dynamically, and items can be added or removed at run time.

Question - Why do you use properties instead of fields?
Answer - You can provide validation code with properties that validate data being read or set. You can not add any validation code while using fields.

Question - Define delegate.
Answer - A delegate acts like a strongly typed function pointer. Delegates can invoke the methods that they reference without making explicit calls to those methods.

Question - Define parse method.
Answer - Parse method is used to convert string value to numeric type. All numeric data type have a Parse method.

Question - Briefly describe kinds of multidimensional arrays.
Answer - Multidimensional arrays are just like a table structure with rows and column. Multidimensional arrays can be either rectangular arrays or jagged arrays. A rectangular array has same number of columns for each row. A Jagged array can contain different number of columns for each row.

Question - What is encapsulation?
Answer -

Question - Define method overloading.
Answer - It allows several methods with the same name but different signatures. It is useful where several similar functionalities are required.

Question - Describe an abstract class.
Answer - An abstract class is a class that cannot be instantiated but must be inherited. It can contain both implemented methods and abstract methods.

Question - Describe Break mode.
Answer - Break mode allows reading code line-by-line. You can observe code in Break mode by using Step Into, Step Over, Step Out, Run To Cursor, and Set Next Statement.

Question - Define Watch window?
Answer - Watch window is used to watch the values of application variables in Break mode.

Question - What is trace? Describe its working.
Answer - Trace produces messages about program conditions even after application is compiled and released without interrupting application execution.

Steps to add Trace in the code.
Create an instance of TextWriterTraceListener and add it to the Listeners collection.
Configure the TextWriterTraceListener to write output to a text file.
Create Trace switches that control when Trace statements are executed.
Compile and deploy the application with Trace defined.
Enable the Trace switches in the application .config file.

Question - Describe exception handling in VB.NET.
Answer - The Try block encapsulate set of code that is error prone and can throw exception. If an exception is thrown, it can be caught in an appropriate Catch (catch) block. You have Finally block that can contain code that must be executed even if no exception is handled.

Question - What is data provider? Explain its components.
Answer - Data Provider is a set of components that facilitate data access.
It contains components like connection, command, dataReader, dataAdapter.
Connection object connects to the data source.
Command object represents a direct command to the data source.
DataReader object that provides connected, forward-only, read-only access to a database.
DataAdapter that provides disconnected data access.