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C++ .NET And Using ADO.NET 2

 

 

What we have in this page?

1. Choosing a .NET Framework Data Provider

2. ADO.NET Namespaces

3. ADO.NET Assemblies

4. Creating a Connected Application

5. Connecting to a Database

 

 

 

 

 

Choosing a .NET Framework Data Provider

 

Depending on the design and data source for your application, your choice of .NET Framework data provider can improve the performance, capability, and integrity of your application. The following table discusses the advantages and limitations of each .NET Framework data provider.

 

 

 

ADO.NET Namespaces

 

The classes in ADO.NET are divided into the six namespaces shown in the following table.

 

 

 

Connecting to a Database

 

In this exercise, you will create a new application to perform all the operations described in the preceding section. The first step is to connect to the database. This exercise uses the Microsoft Northwind database. You may already have a copy if you have Microsoft Office installed on your PC. There is a SQL version of the Northwind sample database that can be downloaded from Microsoft site and also available at Visualcplusdotnet.com. The new version of the SQL database sample is AdventureWorks.

 

1.      Create a Visual C++ CLR Console Application project named ConnectedApplication.

 

 

2.      In the ConnectedApplication.cpp file, after the using namespace System; statement, add the following statements:

// Generic ADO.NET definitions

using namespace System::Data;

// Specific definitions for the OleDb data provider

using namespace System::Data::OleDb;

 

 

If you are using SQL Server 7 or later, you can use the SQL Server data provider instead. To do so, use the System::Data::SqlClient namespace and replace all the class names that begin OleDb with Sql. For example, replace OleDbException with SqlException.

 

3.      In the main() function, create an OleDbConnection object as follows:

// Create the connection

OleDbConnection ^ cnNwind = gcnew OleDbConnection();

 

 

4.      The OleDbConnection object has a ConnectionString property, which enables you to specify the database you want to use. Set the ConnectionString property as follows:

 

// Set the connection string

cnNwind->ConnectionString =

    L" Provider=Microsoft.Jet.OLEDB.4.0; "

    L"Data Source=C:\\temp\\northwind.mdb";

 

This connection string defines a connection to the Northwind database, using the Microsoft Jet database engine. You will need to edit the Data Source path to point to your copy of Northwind. If you are using SQL Server, you’ll need to provide a SQL Server connection string. You’ll also need to connect to a SQL Server version of the Northwind database.

 

5.      Open the database connection as follows:

try

{

  // Open the database

  cnNwind->Open();

  Console::WriteLine(L"Connected to database successfully!");

}

catch (OleDbException ^ pe)

{

  Console::Write(L"Error occurred: ");

  Console::WriteLine(pe->Message);

}

 

 

Just about everything you do with databases can generate an exception. Therefore, you should always enclose your database code in a try and catch block, as shown in the preceding code.

 

 

 

 

6.      At the end of the main() function, close the database connection as follows:

// Close the connection

if (cnNwind->State != ConnectionState::Closed)

{

  cnNwind->Close();

}

Console::WriteLine(L"The database connection is closed...");

 

 

The State property indicates the current state of the connection. The allowable values for this property are defined in the ConnectionState enumerated type, which is located in the System::Data namespace.

 

7.      Build your program, and fix any compiler errors. Run the program. If all is well, you’ll see the message shown in the following figure displayed on the console.

 

 

 

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

 

 

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