Connected vs. Disconnected Architecture in C#

In C# and database programming, there are two primary architectures for working with data: connected and disconnected architectures. Each one of them has its own characteristics and use cases. Let's explore the key differences between these two architectures, illustrated with a source code example and output:

1. Connected Architecture:
   • Characteristics:
     • In a connected architecture, an application maintains an open connection to the database throughout its operation.
     • Data is read directly from the database when needed and is updated in real-time.
     • Changes made by one user are immediately visible to other users.
   • Use Cases:
     • Real-time data requirements, such as financial systems or systems with multiple users concurrently modifying data.
     • When data integrity and consistency across multiple users are critical.
2. Disconnected Architecture:
   • Characteristics:
     • In a disconnected architecture, an application retrieves data from the database, disconnects from the database, and works with the data in memory.
     • Data is cached locally and changes are made to the local copy.
     • Data is updated in the database only when explicitly synchronized.
   • Use Cases:
     • Mobile applications or occasionally connected applications where a continuous database connection is not feasible.
     • Reducing the load on the database server and improving application scalability.

Source Code Example (Connected Architecture):

Here's a simple C# example illustrating a connected architecture using SQL Server:

using System;
using System.Data;
using System.Data.SqlClient;

class Program
{
static void Main()
{
	string connectionString = "Data Source=YourServer;Initial Catalog=YourDatabase;Integrated Security=True";

	using (SqlConnection connection = new SqlConnection(connectionString))
	{
		connection.Open();

		string query = "SELECT * FROM Employees";
		SqlCommand command = new SqlCommand(query, connection);

		SqlDataReader reader = command.ExecuteReader();

		while (reader.Read())
		{
			Console.WriteLine($"Employee ID: {reader["EmployeeID"]}, Name: {reader["FirstName"]} {reader["LastName"]}");
		}

		reader.Close();
	}
}
}

Expected Output (Connected Architecture):

Employee ID: 1, Name: John Smith
Employee ID: 2, Name: Jane Doe
Employee ID: 3, Name: Bob Johnson

Source Code Example (Disconnected Architecture):

Here's a simple C# example illustrating a disconnected architecture using DataSet:

using System;
using System.Data;
using System.Data.SqlClient;

class Program
{
static void Main()
{
	string connectionString = "Data Source=YourServer;Initial Catalog=YourDatabase;Integrated Security=True";

	using (SqlConnection connection = new SqlConnection(connectionString))
	{
		connection.Open();

		string query = "SELECT * FROM Employees";
		SqlDataAdapter adapter = new SqlDataAdapter(query, connection);

		DataSet dataSet = new DataSet();
		adapter.Fill(dataSet, "Employees");

		foreach (DataRow row in dataSet.Tables["Employees"].Rows)
		{
			Console.WriteLine($"Employee ID: {row["EmployeeID"]}, Name: {row["FirstName"]} {row["LastName"]}");
		}
	}
}
}

Expected Output (Disconnected Architecture):

Employee ID: 1, Name: John Smith
Employee ID: 2, Name: Jane Doe
Employee ID: 3, Name: Bob Johnson

In the disconnected architecture example, data is retrieved from the database into a DataSet, and the application can work with the data without maintaining an open database connection. The changes are only persisted to the database when explicitly synchronized.

In summary, the key difference between connected and disconnected architectures in C# is how data is managed: connected architecture maintains a live connection to the database, while disconnected architecture retrieves and caches data locally, reducing the need for a continuous connection. The choice between the two depends on the application's requirements and constraints.