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ADO.Net interview questions and answers

Can you explain the difference between an ADO.NET Dataset and an ADO Record set ?

There two main basic difference between record set and dataset :

  • With dataset you can retrieve data from two databases like oracle and sql server merge them in one dataset , with record set this is not possible
  • All representation of Dataset is using XML while record set uses COM.
  • Record set cannot be transmitted on HTTP while Dateset can be.

How can do pessimistic locking?

Pessimistic locking is done by using transaction isolation levels like read committed, read uncommitted repeatable read and serializable.

What’s difference between “Optimistic” and “Pessimistic” locking?

In optimistic locking there is no locking actually . It only checks if the old values are changed , in case they are changed it means somebody has changed the data, so it raises expection.
In pessimistic locking you actually lock the record, depending on the type of lock no other process can make modifications to the record.

What is difference between dataset and data reader?

Following are some major differences between dataset and data reader :

  • Dataset is a disconnected architecture while data reader is connected architecture.
  • Data Reader provides forward-only and read-only access to data, while dataset moves back as well as forward.
  • Datasetobject is an in-memory database with tables, row and columns while datareader is just simple table which can be read only in a forward direction.
  • Dataset can persist contents while data reader cannot persist contents, they are read only and forward only.

What is the use of command objects?

Command objects helps to execute SQL statements Following are the methods provided by command object :

  • Execute NonQuery : Executes insert, update and delete SQL commands . Returns an Integer indicating the number of rows affected by the query.
  • Execute Reader : Executes select SQL statements which can either be in your .Net code or in a stored procedure, Returns a “Datareader” object.
  • ExecuteScalar : Executes SQL command and returns only a single value like count, sum, first record etc.