.NET (Core and Framework)

Eddy Vluggen9-Sep-09 1:24

Eddy Vluggen

9-Sep-09 1:24

The Using statement usually cleans up[^], that is, if your object is disposable.

Alas, the documentation [^]for SqlConnection states;

MSDN wrote:
If the SqlConnection goes out of scope, it won't be closed. Therefore, you must explicitly close the connection by calling Close or Dispose. Close and Dispose are functionally equivalent. If the connection pooling value Pooling is set to true or yes, the underlying connection is returned back to the connection pool. On the other hand, if Pooling is set to false or no, the underlying connection to the server is actually closed.

I are Troll Smile | :)

Jaime Olivares9-Sep-09 3:13

Jaime Olivares

9-Sep-09 3:13

using will ensure you to dispose an IDisposable-derived object even if you return from inside the "using" block.

Best regards,
Jaime.

DaveyM699-Sep-09 3:49

DaveyM69

9-Sep-09 3:49

connection, command and dataReader will all have their Dispose or IDisposable.Dispose methods called.

Dave

Generic BackgroundWorker - My latest article!
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Why are you using VB6? Do you hate yourself? (Christian Graus)

supercat911-Sep-09 8:02

supercat9

11-Sep-09 8:02

In general, 'Using' is an almost magic bullet to ensure that allocated resources will get freed when used as indicated above. It's not always perfect, however. The biggest gotcha I have found is that a constructor itself creates iDisposable objects which are supposed to get disposed at a later time and an exception is thrown in the constructor, the constructor itself must dispose of those objects, since the partially-constructed object will be going out of scope.

For example, using VB syntax:

Sub New(whatever_arguments...)
  Try
    .. construct the object
  Catch
    Me.Dispose()
    Throw
  End Try
End Sub

Note that the catch block doesn't swallow an exception nor even throw a new one; it simply re-throws the old exception so as to preserve the stack trace.

muktaa15-Sep-09 1:12

muktaa

15-Sep-09 1:12

We can use .net class (Manage code) in using clause it will automatically goes out of scope. You don't need to close or dispose out side, Because they called dispose function.all the class which is implemented the idisposable intercace will work on using clause

Shameel22-Oct-09 5:37

ConfigurationManager: ConfigurationErrorsException after removing config attribute? [RESOLVED]

22-Oct-09 5:37

using keyword is nothing but a syntactic sugar over try-finally construct. For example, the following code

using (SqlConnection conn = new SqlConnection(...)) {
    ....
    ....
    ....
}

actually gets compiled to

SqlConnection conn = new SqlConnection(...);
try {
    ....
    ....
    ....
}
finally {
    if (conn is IDisposable) {
        conn.Dispose();
    }
}

Therefore, irrespective of whether an exception is thrown or a return statement is encountered, the finally blok is always executed and ensures that objects that implement IDisposable are always cleaned up (unless the runtime host chooses not to do so - just to complicate things).

Homncruse8-Sep-09 13:17

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

8-Sep-09 13:17

Exception message:
"Unrecognized attribute 'valid'. Note that attribute names are case-sensitive.

I used to have a field called "valid" in one of my configuration elements, but through the course of development it's now obsolete, so I'd like to remove it. I removed it from the ConfigurationElement subclass, and now when I try to read the config section (via config.GetSection), I get the above exception, which then makes my config section variable null, blah blah blah, no saved config = program effectively unusable from session to session.

Google fails me. MSDN fails me. Internet fails me.

I'm new to the ConfigurationManager, having only ever done equivalent functionality through .ini files before, so I'm sure there's probably just some "cleanup" command I can do that I'm just not aware of.

modified on Friday, October 23, 2009 2:41 PM

Shameel22-Oct-09 5:41

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

22-Oct-09 5:41

I believe you are writing a class to read configuration values from a config class. You have removed the 'valid' element from the spec but not from the config file. I think, removing the 'valid' element from the config file should solve your problem.

Homncruse22-Oct-09 6:36

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

22-Oct-09 6:36

Yes, that's more or less the problem, but since it's using the ConfigurationManager, the actual config file operations are completely hidden (as far as I know), or at least I don't know where to find it.

Shameel22-Oct-09 8:56

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

22-Oct-09 8:56

What kind of app r u developing? Windows or Web ? Whatever it is you should have full control over your config files.

Homncruse22-Oct-09 9:34

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

22-Oct-09 9:34

It's a Windows app using the built-in ConfigurationManager .NET capabilities. I based it on this MSDN code sample[^]. Maybe it'll be easier to just show some code:

Configuration classes:

public class SerialConfig : ConfigurationElement
    {
        /* *********************************** */
        /* This is the field I want to remove! */
        /* *********************************** */      
        // Fields
        [ConfigurationProperty("valid",
            DefaultValue = false,
            IsRequired = false)]
        //private int baud;
        public bool Valid
        {
            get
            {
                return (bool)this["valid"];
            }
            set
            {
                this["valid"] = (bool)value;
            }
        }


        [ConfigurationProperty("baud",
            DefaultValue = 115200,
            IsRequired = true)]
        //private int baud;
        public int Baud
        {
            get
            {
                return (int)this["baud"];
            }
            set
            {
                if((value == 115200) || (value == 9600))
                {
                    this["baud"] = value;
                }
                else
                {
                }
            }
        }

        [ConfigurationProperty("name",
            DefaultValue = "",
            IsRequired = true)]
        //private String name;
        public String Name
        {
            get
            {
                return (string)this["name"];
            }
            set
            {
                if (value.Contains("COM"))
                {
                    this["name"] = value;
                }
                else
                {
                    this["name"] = "INVALID";
                }
            }
        }
        
        // Constructors
        public SerialConfig(String name, int baud)
        {
            this["baud"] = baud;
            this["name"] = name;            
        }

        public SerialConfig(string name)
        {
            new SerialConfig(name, 115200);
        }

        public SerialConfig()
        {
            new SerialConfig("INVALID", 115200);
        }
    }

    // Define a custom section that is used by the application
    // to create custom configuration sections at the specified 
    // level in the configuration hierarchy that is in the 
    // proper configuration file.
    // This enables the user that has the proper access 
    // rights, to make changes to the configuration files.
    public class SerialConfigSection : ConfigurationSection
    {
        // Create a configuration section.
        public SerialConfigSection()
        {
            this["serialConfig"] = new SerialConfig();
        }

        // Set or get the SerialConfig. 
        [ConfigurationProperty("serialConfig")]
        public SerialConfig serialConfig
        {
            get
            {
                return (
                  (SerialConfig)this["serialConfig"]);
            }
            set
            {
                this["serialConfig"] = value;
            }
        }
    }

Actual usage of configuration

/// <summary>
/// Reads stored configuration settings from
/// ConfigurationUserLevel.PerUserRoamingAndLocal,
/// creating new default entries if corrupted or not present.
/// </summary>
public static void InitializeConfig()
{
    // Get the configuration that applies to the current user.
    Configuration userConfig =
        ConfigurationManager.OpenExeConfiguration(
            ConfigurationUserLevel.PerUserRoamingAndLocal);

    // Map the configuration file. This enables the application to access
    // the configuration file using the System.Configuration.Configuration
    // class
    ExeConfigurationFileMap configFileMap =
        new ExeConfigurationFileMap();
    configFileMap.ExeConfigFilename =
        userConfig.FilePath;

    // Get the mapped configuration file.
    config =
        ConfigurationManager.OpenMappedExeConfiguration(
            configFileMap, ConfigurationUserLevel.None);

    // Try to read the config file settings for the serial ports
    EITPortConfig = null;
    BridgePortConfig = null;

    try
    {
        EITPortConfig = (SerialConfigSection)config.GetSection("EITCOMPort");
        BridgePortConfig = (SerialConfigSection)config.GetSection("BridgeCOMPort");

        // Synchronize the application configuration
        // if needed. The following two steps seem
        // to solve some out of synch issues
        // between roaming and default
        // configuration.
        config.Save(ConfigurationSaveMode.Modified);

        // Force a reload of the changed section,
        // if needed. This makes the new values available
        // for reading.
        ConfigurationManager.RefreshSection("EITCOMPort");
        ConfigurationManager.RefreshSection("BridgeCOMPort");

        // If we couldn't retrieve the EITPort section from the config
        if (EITPortConfig == null)
        {
            EITPortConfig = new SerialConfigSection();

            // Define where in the configuration file
            // hierarchy the associated
            // configuration section can be declared.
            // The following assignment assures that
            // the configuration information can be
            // defined in the user.config file in the
            // roaming user directory.
            EITPortConfig.SectionInformation.AllowExeDefinition =
              ConfigurationAllowExeDefinition.MachineToLocalUser;

            // Allow the configuration section to be
            // overridden by lower-level configuration files.
            // This means that lower-level files can contain
            // the section (use the same name) and assign
            // different values to it.
            EITPortConfig.SectionInformation.AllowOverride = true;

            // Add configuration information to
            // the configuration file.
            config.Sections.Add("EITCOMPort", EITPortConfig);
            config.Save(ConfigurationSaveMode.Modified);
            // Force a reload of the changed section. This
            // makes the new values available for reading.
            ConfigurationManager.RefreshSection("EITCOMPort");
        }

        // If we couldn't retrieve the EITPort section from the config
        if (BridgePortConfig == null)
        {
            BridgePortConfig = new SerialConfigSection();

            // Define where in the configuration file
            // hierarchy the associated
            // configuration section can be declared.
            // The following assignment assures that
            // the configuration information can be
            // defined in the user.config file in the
            // roaming user directory.
            BridgePortConfig.SectionInformation.AllowExeDefinition =
              ConfigurationAllowExeDefinition.MachineToLocalUser;

            // Allow the configuration section to be
            // overridden by lower-level configuration files.
            // This means that lower-level files can contain
            // the section (use the same name) and assign
            // different values to it.
            BridgePortConfig.SectionInformation.AllowOverride = true;

            // Add configuration information to
            // the configuration file.
            config.Sections.Add("BridgeCOMPort", BridgePortConfig);
            config.Save(ConfigurationSaveMode.Modified);
            // Force a reload of the changed section. This
            // makes the new values available for reading.
            ConfigurationManager.RefreshSection("BridgeCOMPort");
        }

    }
    catch (ConfigurationErrorsException e)
    {
        Console.WriteLine("[Exception error: {0}]", e.ToString());
    }
}

Shameel23-Oct-09 8:23

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

23-Oct-09 8:23

Your solution must have a default configuration file (app.config) that is used as a template to create local copies during deployment. For example, if you app name is myapp.exe, then your configuration file name during deployment is myapp.exe.config. Changing the app.config should solve your problem.

Shameel23-Oct-09 8:25

Re: ConfigurationManager: ConfigurationErrorsException after removing config attribute?

23-Oct-09 8:25

In the InitializeConfig() method, debug and check the value of userConfig.FilePath property. I think that should tell you the configuration file path.

Homncruse23-Oct-09 8:41