Usage and Importance of Using in C#

using System.IO;
using System.Text;

using MyProject = TruckingApp.Services;  

MyProject.Truck newObj = new MyProject.Truck();  

using namespace1 = TruckingApp1.Services;  
using namespace2 = TruckingApp2.Services;  
using namespace3 = TruckingApp3.Services;  
   
namespace2.Truck newObj = new namespace2.Truck();  

TruckingApp.Services2.Truck newObj = new TruckingApp.Services2.Truck();  

You can do the same as what the using statement is doing by using try-catch block and calling the Dispose() inside the finally block explicitly. But the using statement does the calls automatically to make the code cleaner and more elegant. Within the using block, the object is read-only and cannot be modified or reassigned.

Let's explain how to implement the using statement in ADO.NET, calling WebService, IO operations, EntityFramework and so on.

ADO.NET

string connString = "Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;";  
   
using (SqlConnection conn = new SqlConnection(connString))  
{  
      SqlCommand cmd = conn.CreateCommand();  
      cmd.CommandText = "SELECT CustomerId, CompanyName FROM Customers";  
      conn.Open();  
   
      using (SqlDataReader dr = cmd.ExecuteReader())  
      {  
         while (dr.Read())  
         Console.WriteLine("{0}\t{1}", dr.GetString(0), dr.GetString(1));  
      }  
}

In the preceding code I am not closing any connection, it will close automatically. The using statement will call conn.Close() automatically due to the using statement (using (SqlConnection conn = new SqlConnection(connString)) and the same for a SqlDataReader object.

And also if any exception occurs it will close the connection automatically.

Entity Framework

The using statement can also be used in EntityFramework and Transaction.

Code

public string GetDriver()  
{  
      try  
      {  
            // Creating Transaction object through using statemnt  
            using (TransactionScope trans = new TransactionScope())  
            {  
                  // Creating entity framework connection object through Using statement  
                  using (TruckingDBEntities cc = new TruckingDBEntities ())  
                  {  
                        // Getting employee list  
                        List<emp> empList = (from temp in cc.Employees  
                                                        Where temp.name = “manas”  
                                                        Select temp).ToList();  
                  }  
               // Means all operations are successful and needs to commit.  
                trans.Complete();  
         }  
   }  
   catch (Exception ex)  
   {  
         // Log error for future reference  
   }  
}

Web Service

These days, a web service call is often used in our applications. We can also use the using statement when calling a web service. Once we call the web service if we forgot to dispose of the object then the using statement helps in closing and disposing of the object because web service objects are heavy.

Code

// Calling Webserice with username and password  
using (TruckServiceClient sc = new TruckServiceClient())  
{  
      // Appending username and password to request  
      sc.ClientCredentials.UserName.UserName = "uid";  
      sc.ClientCredentials.UserName.Password = "pwd";  
   
      // Calling webs service method  
      string returndata = sc.GetData(100);  
}

IO operations

The using statement can also be used when we do any kind of IO operations. It also helps to dispose of IO objects.

Code

try  
{  
    using (StreamWriter sw = File.AppendText(filePath))  
    {  
        sw.WriteLine(message);  
    }  
}  
catch(Exception ex)  
{  
   // Handle exception  
} 

Lastly we can implement the using statement in custom classes like:

Class Emloyee  
{  
   Public void getEmp()  
   {  
      // Do some operations  
   }  
}

Call the Employee class method using the using statement as in the following:

Using(Employee emp = new Employee())  
{  
   emp.getEmp();  
}

From the preceding discussion, you can understand that the "using" keyword plays a vital role.

First, to add a namespace as a type, or a namespace as an alias.

Secondly, to dispose of and close the objects wisely. It enhances the performance of an application.

Please extensively use the using statement in projects.

I hope it helps you to understand the usage and importance of the using keyword in C#.

Happy coding!