Interview Questions And Answers on ADO.NET in C#(part 1)

 1.What is Microsoft ADO.NET?
 

 Visual Studio .NET provides access to databases through the set of tools and namespaces collectively referred to as Microsoft ADO.NET

 2. What are the 3 major types of connection objects in ADO.NET? 

 OleDbConnection object : Use an OleDbConnection object to connect to a Microsoft  Access or third-party database, such as MySQL. OLE database connections use the OleDbDataAdapter object to perform commands and return data.

SqlConnection object : Use a SqlConnection object to connect to a Microsoft SQL Server database. SQL database connections use the SqlDataAdapter object to perform commands and return data.

OracleConnection object : Use an OracleConnection object to connect to Oracle databases. Oracle database connections use the OracleDataAdapter object to perform commands and return data. This connection object was introduced in Microsoft .NET Framework version 1.1.

3.List the 4 common ADO.NET Namespaces?

System.Data : Contains Classes, types, and services for creating and accessing data sets and their subordinate objects.

System.Data.SqlClient : Contains Classes and types for accessing Microsoft SQL Server databases.

System.Data.OracleClient : Contains Classes and types for accessing Oracle databases (Microsoft .NET Framework version 1.1 and later).

System.Data.OleDb : Contains Classes and types for accessing other databases

4 What is the difference between Data Reader and Data Adapter? 

1. Data Reader is read only forward only and much faster than Data Adapter.

2. If you use Data Reader you have to open and close connection explicitly where as if you use  Data Adapter the connection is automatically opened and closed.

 3. Data Reader is connection oriented where as Data Adapter is disconnected.

5.Will the connection be closed, if the SqlConnection object goes out of scope? 

No, If the SqlConnection goes out of scope, it won't be closed. Therefore, you must explicitly close the connection by calling Close or Dispose.

6.How do you read an XML file into a DataSet?

 Using the DataSet object’s ReadXML method.

7.When do you use ExecuteReader, ExecuteNonQuery, ExecuteScalar methods? If the command or stored procedure that is being executed returns a set of rows, then  we use ExecuteReader method. If the command or stored procedure that is being executed returns a single value then  we use ExecuteScalar method. If the command or stored procedure performs INSERT, DELETE or UPDATE operations, then we use ExecuteNonQuery method. ExecuteNonQuery method returns an integer specifying the number of rows inserted, deleted or updated. 8.How can you  identify the updated rows in a dataset? Using Rowstate property of the DataRow.If the RowState property of the DataRow is "Modified" then that DataRow can be treated as updated. 9.what is capacity of dataset? DataSet is logical represantation of database so it can store as much as database. 10 Can your class inherit from SqlCommand Class?  No, you cannot inheirt from SqlCommand Class. SqlCommand Class is a sealed class. It is a compile time error. 11.What is  Source?  It can be a database, text file, excel spread sheet or an XML file. 12.What is dataprovider?   A set of libraries that is used to communicate with data source.  Eg:  SQL data provider for SQL, Oracle data provider for Oracle, OLE DB data provider for access, excel or mysql. 13.What is SqlCommand? It allows to manipulate database by executing stored procedure or sql statements. 14.What is DataReader?  It provides a forward-only, read-only, connected recordset. 15.What is DataSet?  Dataset is a disconnected, in-memory representation of data.  It can contain multiple data table from different database. 16.What is SQL DataAdapter?   It populates dataset from data source.  It contains a reference to the connection object and opens and closes the connection automatically when reading from or writing to the database. 17.what is DataView?   It provides a means to filter and sort data within a data table. 18.What is the feature of the CommandBuilder class? Implementation of INSERT, DELETE and UPDATE commands is automatic and this class provides the necessary automation. You cannot extend or change the command builder while keeping the base algorithmintact to create action statements. 19.What are the two fundamental objects in ADO.NET? Data reader and Dataset are the two fundamental objects in ADO.NET. 20.What are major difference between classic ADO and ADO.NET? Following are some major differences between both :- In ADO we have recordset and in ADO.NET we have dataset. In recordset we can only have one table. Dataset can have multiple tables. All data persist in XML as compared to classic ADO where data persisted in Binary format also. 21.What is the use of connection object? It is used to connect a data to a Command object.  An OleDbConnection object is used with an OLE-DB provider A SqlConnection object uses Tabular Data Services (TDS) with MS SQL Server 22.What is the use of data adapter? These objects connect one or more Command objects to a Dataset object. They provide logic that would get data from the data store and populates the tables in the Dataset, or pushes the changes in the Dataset back into the data store.  An OleDbDataAdapter object is used with an OLE-DB provider .A SqlDataAdapter object uses Tabular Data Services with MS SQL Server. 23. What is connection pooling?  Connection pooling refers to the task of grouping database connections in cache to make them reusable because opening new connections every time to a database is a time-consuming process. Therefore, connection pooling enables you to reuse already existing and active database connections, whenever required, and increasing the performance of your application. You can enable or disable connection pooling in your application by setting the pooling property to either true or false in connection string. By default, it is enabled in an application. 24.Difference between dataset and datareader?  Dataset: DataSet object can contain multiple rowsets from the same data source as well as from the relationships between them. Dataset is a disconnected architecture. Dataset can persist data. Datareader: DataReader provides forward-only and read-only access to data. Datareader is connected architecture. Datareader can not persist data. 25   Which properties are used to bind a DataGridView control?                                                                                  The DataSource property and the DataMember property are used to bind  a DataGridView control. 26 What is the difference between the Clone() and Copy() methods of the DataSet class?  The Clone() method copies only the structure of a DataSet. The copied structure includes all the relation, constraint, and DataTable schemas used by the DataSet. TheClone() method does not copy the data, which is stored in theDataSet.The Copy() method copies the structure as well as the data stored in the DataSet. 27  What are basic methods of a DataAdapter? Fill FillSchema   Update  28 How can we connect to Microsoft Access ,Foxpro , Oracle etc ? Microsoft provides System.Data.OleDb namespace to communicate with databases like Access, Oracle etc. In short any OLE DB-Compliant database can be connected using System.Data.OldDb namespace. 29  Which is the best place to store connectionstring in .NET projects? Config files are the best places to store connectionstrings. If it is a web-based application “Web.config” file will be used and if it is a windows application “App.config” files will be used. 30 How can we save all data from dataset ? Dataset has “AcceptChanges” method which commits all the changes since last time “Acceptchanges” has been executed. 31 Can you edit data in the Repeter control? No, it just reads the information from its data source 32 Can DataAdapter object accept DataTable as parameter in Fill method? DataAdapter object can accept either DataTable or DataSet as parameter to fill data from database. 33 Which is better data reader or dataset?                           It depends upon the requirement .whenever we need only access data, DataReader is better. 34 Which adapter should you use, if you want to get the data from an Access database? OleDbDataAdapter is used to get the data from an Access database. 35 How do we use stored procedure in ADO.NET and how do we provide parameters to the stored procedures? ADO.NET provides the SqlCommand object, which provides the functionality of executing stored procedures