ADO.NET Interview Preparation Guide
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ADO.NET Interview Questions and Answers will guide us now that ADO.NET is a set of computer software components that can be used by programmers to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems, though it can also be used to access data in non-relational sources. Learn ADO.NET with ADO.NET Interview Questions and Answers

42 ADO.NET Questions and Answers:

1 :: What is ADO.NET?

ADO.NET is a part of the Microsoft .NET Framework. This framework provides the set of classes that deal with data communication between various layers of the software architecture and the database. It provides a continuous access to different data source types such as SQL Server versions 7, 2000, 2005. It also provides connectivity options to data sources through OLE DB and XML. Connectivity may be established with other databases like Oracle, MySQL etc. as well.

ADO.NET has the ability to separate data access mechanisms, data manipulation mechanisms and data connectivity mechanisms.

ADO.NET introduces along with it the disconnected architecture. In a disconnected architecture, data may be stored in a DataSet. It contains providers for connecting to databases, commands for execution and retrieval of results.

The classes for ADO.NET are stored in the DLL System.Data.dll.
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2 :: can we connect two dataadapters to same data source using single connection at same time?

yes,we can connect two dataadapters to same datasource using single connection at same time.
There is a technology in ado.net 2.0 called MARS usinng Mars in connection string we can do it.
for eg:
cn.ConnectionString = "server=(local); database=employee; integrated security=sspi; MultipleActiveResultSets=True";
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3 :: Can we do database operations without using any of the ADO.net objects?

No its not at all possible.
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4 :: If we are not returning any records from the database, which method is to be used?

There is a method called Execute Non Query. This method executes the Update, Delete etc. This does not return any rows but will give the number of rows affected.
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5 :: how can i retrieve two tables of data at a time by using data reader?
Data reader read and forward only, how is it possible to get 2 tables of data at a time?

yes this is possible

If we execute 2 select command either in stored procedure or in select command and then executereader method fired of command object. it return 2 tables in datareader.

like :
string str="Select * from a;select * from b";
cmd.commandtext=str;
dr=cmd.executereader();

Now it return 2 tables in datareader (dr).
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6 :: Explain ExecuteNonQuery?

// Summary:

// Executes a Transact-SQL statement against the connection and returns the number of rows affected.

// Returns:

// The number of rows affected.
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7 :: What is the ExecuteScalar method?

// Summary:

Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.

// Returns:

The first column of the first row in the result set, or a null reference (Nothing in Visual Basic) if the result set is empty.
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8 :: Which one of the following objects is a high-level abstraction of the Connection and Command objects in ADO.NET?

DataReader DataSet DataTable DataView DataAdapter

Answer: DataAdapter
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9 :: How can we load multiple tables in to Dataset?

DataSet ds=new DataSet();

SqlDataAdapter dap=new SqlDataAdapter(Select * from <tablename>,<connection1>);

dap.Fill(ds,"TableOne");

SqlDataAdapter dap1=new SqlDataAdapter(Select * from <tablename>,<connection1>);

dap1.Fill(ds,"tableTwo");
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10 :: What is connection String?

connection String - a string which contains address of the database we want to connect to.
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