SqlDataReader.Close Method
Assembly: System.Data (in system.data.dll)
You must explicitly call the Close method when you are through using the SqlDataReader to use the associated SqlConnection for any other purpose.
The Close method fills in the values for output parameters, return values and RecordsAffected, increasing the time that it takes to close a SqlDataReader that was used to process a large or complex query. When the return values and the number of records affected by a query are not significant, the time that it takes to close the SqlDataReader can be reduced by calling the Cancel method of the associated SqlCommand object before calling the Close method.
 Caution |
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| Do not call Close or Dispose on a Connection, a DataReader, or any other managed object in the Finalize method of your class. In a finalizer, you should only release unmanaged resources that your class owns directly. If your class does not own any unmanaged resources, do not include a Finalize method in your class definition. For more information, see Garbage Collection. |
The following example creates a SqlConnection, a SqlCommand, and a SqlDataReader. The example reads through the data, writing it out to the console window. The code then closes the SqlDataReader. The SqlConnection is closed automatically at the end of the using code block.
private static void ReadOrderData(string connectionString) { string queryString = "SELECT OrderID, CustomerID FROM dbo.Orders;"; using (SqlConnection connection = new SqlConnection(connectionString)) { SqlCommand command = new SqlCommand(queryString, connection); connection.Open(); SqlDataReader reader = command.ExecuteReader(); // Call Read before accessing data. while (reader.Read()) { Console.WriteLine(String.Format("{0, {1", reader[0], reader[1])); // Call Close when done reading. reader.Close();
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
If you attempt to close the SqlDataReader before you have read all the rows, the Close operation will retrieve the remaining data from the stream. If there is a significant amount of data left in the stream, this may take long enough to cause a timeout exception.
The solution is to use the Cancel method on the SqlCommand used to open the DataReader. You can also restrict the result set to be smaller if you don't intend to use all of it.
- 9/13/2006
- Speedbird186
