what is Ado.Net

To understand ADO.Net, analyze the figure shown below.

From the above figure, it is very clear that every application whether it be a web application like Asp.Net web Forms app and Asp.Net MVC app or a Desktop application like WPF app or Winforms app or a Web Service like Web API or WCF, needs to communicate to a data source like SQL Server, but SQL Server doesn't understand .Net languages Like c# or VB, then a big a question that arises in mind is how to communicate with data sources like SQL Server from any .Net Application, Here comes the Ado.Net, DO.NET is the core data access technology for .NET languages. With the help of Ado.Net, we can communicate to Data Sources like SQL Server using our favorite Language c# or VB. You can think of ADO.NET, as a set of classes or a sort of framework, that can be used to interact or communicate with data sources like Databases and XML files, the data can then be consumed in any .NET application whether it be a desktop application or web application, etc. ADO stands for Microsoft ActiveX Data Objects.

How does Sql Server understand C#?

Databases only understand SQL. If a .NET application (Web, Desktop, Console etc.) has to retrieve data, then the application needs to
    1. Connect to the Database
    2. Prepare an SQL Command
    3. Execute the Command
    4. Retrieve the results and display in the application

Ado.Net provides some classes that enables us to accomplish all these task , for example if we want to communicate with Sql Server then we can use following code.

 SqlConnection con = new SqlConnection("data source=.; database=Sample; integrated security=SSPI");
 SqlCommand cmd = new SqlCommand("Select * from tblEmplpoyee", con);
 con.Open();
 SqlDataReader rdr = cmd.ExecuteReader();
 GridView1.DataSource = rdr;
 GridView1.DataBind();
 con.Close();

Please Notice that we are using objects of classes like SQLConnection, SQLCommand and SQLDataReader classes where All these objects are prefixed with the word SQL, because they reprsent the same data source that is Sql Server, All these classes are present in System.Data.SqlClient namespace, so importe this namespace before using thses objects.

So, we can say that System.Data.SqlClient is the .Net data provider for SQL Server.

Similarly follow below code to connect to Oracle Database and retrieve data.

   OracleConnection con = new OracleConnection("Oracle Database Connection String");
  OracleCommand cmd = new OracleCommand("Select * from tblEmployee", con);
  con.Open();
  OracleDataReader rdr = cmd.ExecuteReader();
  GridView1.DataSource = rdr;
  GridView1.DataBind();
  con.Close();

Notice here we are using OracleConnection, OracleCommand and OracleDataReader classes and their objects are prefixed with the word Oracle because the data provider is OracleClient, so, please don't forget to import namespace System.Data.OracleClient as all these classes are present in this namespace only.

So, we can say that the .NET data provider for Oracle is System.Data.OracleClient.

Similarly,If we want to connect to OLEDB datasources like Excel, Access etc, we can use OleDbConnection, OleDbCommand and OleDbDataReader classes.

So, .NET data provider for OLEDB is System.Data.OleDb.

Thus we have following .NET Data Providers
    Data Provider for SQL Server is System.Data.SqlClient
    Data Provider for Oracle is System.Data.OracleClient
    Data Provider for OLEDB is System.Data.OleDb
    Data Provider for ODBC is System.Data.Odbc
   

Please note that, depending on the provider, the following ADO.NET objects have a different prefix
  1. Connection - SQLConnection for Sql Server, OracleConnection for oracle, OleDbConnection and OdbcConnection for MSAccess etc
  2. Command - SQLCommand for SQL Server, OracleCommand for Oracle Server, OleDbCommand and OdbcCommand for MSAccess etc
  3. DataReader - SQLDataReader for SQL Server, OracleDataReader for Oracle, OleDbDataReader and OdbcDataReader for MSAccess etc
  4. DataAdapter - SQLDataAdapter for SQL Server, OracleDataAdapter for Oracle, OleDbDataAdapter and OdbcDataAdapter for MSAccess etc

The DataSet object is not provider-specific. Once we connect to a Database, execute the command, and retrieve data into the .NET application. The data will be stored in a DataSet and work independently of the database. we will discuss DataSet and DataAdapter in later articles.