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Using Statement In C#

In this article, we will discuss the using statement in C#.

Purpose

Consider the following example: -

SqlConnection connection = new SqlConnection(connectionString);
SqlDataReader reader = null;

SqlCommand cmd = new SqlCommand(commandString, connection);
connection.Open();
reader = cmd.ExecuteReader();

while (reader.Read()) {
  listBox1.Items.Add(reader[0].ToString() + ", " + reader[1].ToString());
}

reader.Close();
connection.Close();

In the above example, the data is fetched from the database and bound to the Listbox. In case of any exception say on "listBox1.Items.Add()", the code will not execute further.

So, the reader and the connection will be in the open state because the below code will not execute.

reader.Close();
connection.Close();

To avoid this scenario, we have 2 options: -

Use the Try-Catch-Finally block and close Datareader and connection in the Finally block
Use the "using" statement to ensure that the Datareader and connection object will be closed before exiting the loop

Using Statement In Action

With the "using" statement, the above code is changed to: -

using(SqlConnection connection = new SqlConnection(connectionString)) {
  SqlCommand cmd = new SqlCommand(commandString, connection);
  connection.Open();

  using(SqlDataReader reader = cmd.ExecuteReader()) {
    while (reader.Read()) {
      listBox1.Items.Add(reader[0].ToString() + ", " + reader[1].ToString());
    }
  }
}

Posted By -	Karan Gupta

Posted On -	Tuesday, November 30, 2010

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