This is not the place for a singleton and the singleton is not implemented
correctly since it doesn't take into account any race conditions that might
occur with a multi-threaded app such as asp.net. Also you would not want to
dispose of the connection in the singleton since that defeats the purpose of
the singleton.
The connection should be created and destroyed when needed and not kept live
by using the singleton.
On 10/16/07, Abhijit Gadkari <[EMAIL PROTECTED]> wrote:
>
> We are writing an ASP.NET application. We have used singleton for
> instantiating a database connection as explained in the following code
> sample.
>
>
>
> Design thought was to use only one instance of MyDb across all the pages
> in
> this web application. Is this a correct singleton implementation for
> Asp.NETweb application for managing database connection? In fact, this
> code got C –
> or D in our internal code review. Don't know why? Any idea on how to
> improve
> this code to A level.
>
>
>
> public sealed class AppDbProvider : IDisposable
>
> {
>
> public static readonly AppDbProvider instance = new
> AppDbProvider();
>
>
>
> private readonly MyDb _d = new MyDb(ConfigurationManager
> .ConnectionStrings["my_connection"].ConnectionString,
>
> ConfigurationManager.ConnectionStrings[
> "my_connection"].ProviderName);
>
>
>
> public MyDb GetDbConnection()
>
> {
>
> if (_d != null)
>
> return _d;
>
> else
>
> throw new Exception("Problem with Database Connection in
> AppDbProvider.");
>
> }
>
>
>
> #region IDisposable Members
>
>
>
> public void Dispose()
>
> {
>
> if (_d != null)
>
> _d.Dispose();
>
>
>
> Dispose();
>
>
>
> }
>
>
>
> #endregion
>
> }
>
>
>
> Now in code behind file, we have following code
>
>
>
>
>
> public partial class CreatePage
>
> {
>
> private AmgDb _d;
>
>
>
> try
>
> {
>
> _d = AppDbProvider.instance.GetDbConnection();
>
> }
>
> Catch (Exception exce)
>
> {
>
> Response.write(exce.message);
>
> }
>
>
>
> }
>
>
>
> And in the end, in the page unload event we have following cleanup code
>
>
>
> protected void Page_Unload(object sender, EventArgs e)
>
> {
>
> if (_d != null)
>
> {
>
> _d = null;
>
> }
>
> }
>
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