Programmatically Change Values in Configuration File During Runtime in C# & VB

In this post, I will show you guys on how to programmatically change the values defined in configuration file. [Thanks to Serena Yeoh for introduce this to me.]

"Be aware that it is not recommended to change the value in web application's configuration file, this is due to changing of the configuration file will cause the application pool to restart. What this means is that the value kept in session or in static will be lost."

Well, don't be scared off by the statement. It doesn't mean that you can't use it in different environment. There might be a situation that requires you to change the value in configuration file, such as the value defined in configuration file changes the way how your application behaves and you want to test these behaviors in your Unit Test. Changing the configuration value manually and re-run the test can be very tedious and other developers that are sharing/developing the same project might not be aware about this.

To deal with this kind of situation, you will need to change them in code. So let's get started.

You need to have an instance of Configuration. By calling the following code, it will retrieve the current project's configuration file (app.config).

[C#]

var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

[VB]

Dim config As Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)

If your application is using a custom configuration and wants to change the value in the custom configuration, you will need to get the instance of the section. Assuming my section's name is "sampleSectionGroup/changeConfiguration".

[C#]

var configSection = (ChangeConfigurationSection)config.GetSection("sampleSectionGroup/changeConfiguration");

[VB]

Dim configSection = CType(config.GetSection("sampleSectionGroup/changeConfiguration"), ChangeConfigurationSection)

With the configuration retrieved, you can then change the configuration value. The following code is used to change the value in appSettings. Assuming my appSettings contain keys with the name "sampleAppKeyOne" and "sampleAppKeyTwo".

[C#]

config.AppSettings.Settings["sampleAppKeyOne"].Value = "NewSampleAppKeyOne";

config.AppSettings.Settings["sampleAppKeyTwo"].Value = "NewSampleAppKeyTwo";

[VB]

config.AppSettings.Settings("sampleAppKeyOne").Value = "NewSampleAppKeyOne"

config.AppSettings.Settings("sampleAppKeyTwo").Value = "NewSampleAppKeyTwo"

The following code is used to change the value in a custom made configuration. Assuming my element name is "sampleConfig" that contain 2 string attribute "samplePropertyOne" and "samplePropertyTwo".

[C#]

configSection.SampleConfig.SamplePropertyOne = "NewSamplePropertyOne";

configSection.SampleConfig.SamplePropertyTwo = "NewSamplePropertyTwo";

[VB]

configSection.SampleConfig.SamplePropertyOne = "NewSamplePropertyOne"

configSection.SampleConfig.SamplePropertyTwo = "NewSamplePropertyTwo"

Once you have done changing the value. You need to save them back to the configuration file.

[C#]

config.Save(ConfigurationSaveMode.Modified);

[VB]

config.Save(ConfigurationSaveMode.Modified)

If you have the need to access the updated value from the configuration file immediately after the changes is saved to the configuration file. you need to refresh the section that you have changed. So if let's say the appSettings and the custom configuration's value is changed and need to get the updated value from the configuration file. those section needs to be refreshed by calling the following code.

[C#]

ConfigurationManager.RefreshSection("appSettings");

ConfigurationManager.RefreshSection("sampleSectionGroup/changeConfiguration");

[VB]

ConfigurationManager.RefreshSection("appSettings")

ConfigurationManager.RefreshSection("sampleSectionGroup/changeConfiguration")

The sample code can be obtained here https://onedrive.live.com/redir?resid=E6612168B803803D!331&authkey=!AGahxzzrDJsW3MM&ithint=file%2czip

Using MSMQ with WCF in C# & VB

You might come across a situation where data doesn't need to be process immediately or the data can be processed at a later time. There might be also a situation where you need to pass the data to another client that are currently offline or not available. In such a case, you opt for MSMQ to deal with these situations. Before continue reading, you need to have knowledge on what MSMQ is all about. So, if you are new to MSMQ, do take a look on the following link https://msdn.microsoft.com/en-us/library/ms711472(v=vs.85).aspx.

Now I'm going to show you how to implement MSMQ with WCF. This means that the application will send and receive message from the queue through service. Other than that, transactional queue will be used to perform retry on the queue message.

Firstly, implement a service and contract for receiving and processing the message in the queue. The parameter TransactionScopeRequired in the OperationBehavior needs to be set to true. This is to ensure that whenever there's an exception that prevents the method from complete, it will go back to the queue. For more detail about Transacted MSMQ binding, you can check it out from here https://msdn.microsoft.com/en-us/library/ms751493(v=vs.110).aspx.

[C#]

[ServiceContract]

public interface IRecoveryService

{

    [OperationContract(IsOneWay = true)]

    void Log(string value);

}

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Single)]

public class RecoveryService : IRecoveryService

{

    [OperationBehavior(TransactionScopeRequired = true)]

    public void Log(string value)

    {

        // Do your stuff

    }

}

[VB]

<ServiceContract>

Public Interface IRecoveryService

    <OperationContract(IsOneWay:=True)>

    Sub Log(ByVal value As String)

End Interface

<ServiceBehavior(InstanceContextMode:=InstanceContextMode.PerCall, ConcurrencyMode:=ConcurrencyMode.Single)>

Public Class RecoveryService

    Implements IRecoveryService

    <OperationBehavior(TransactionScopeRequired:=True)>

    Public Sub Log(value As String) Implements IRecoveryService.Log

        ' Do your stuff

    End Sub

End Class

The following are the sample configuration for hosting msmq with WCF. Assuming that my queue is a transactional private queue with the name wcfmsmq and my msmq service name is RecoveryService.

<system.serviceModel>

  <serviceHostingEnvironment multipleSiteBindingsEnabled="true">

    <serviceActivations>

      <add factory="System.ServiceModel.Activation.ServiceHostFactory" relativeAddress="./RecoveryService.svc" service="WCFMSMQVB.Services.RecoveryService" />

    </serviceActivations>

  </serviceHostingEnvironment>

  <services>

    <service name="WCFMSMQVB.Services.RecoveryService" behaviorConfiguration="DefaultServiceBehavior">

      <endpoint name="netMsmqRecoveryService" address="net.msmq://localhost/private/wcfmsmq" binding="netMsmqBinding" bindingConfiguration="netMsmq" contract="WCFMSMQVB.Services.Contracts.IRecoveryService" />

      <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />

    </service>

  </services>

  <behaviors>

    <serviceBehaviors>

      <behavior name="DefaultServiceBehavior">

        <serviceMetadata httpGetEnabled="true" />

        <serviceDebug includeExceptionDetailInFaults="true" />

      </behavior>

    </serviceBehaviors>

  </behaviors>

  <bindings>

    <netMsmqBinding>

      <binding name="netMsmq" maxReceivedMessageSize="2147483647" maxRetryCycles="3" retryCycleDelay="00:00:05" receiveErrorHandling="Drop">

        <security mode="None">

          <transport msmqAuthenticationMode="None" msmqProtectionLevel="None" />

        </security>

      </binding>

    </netMsmqBinding>

  </bindings>

  <client>

    <endpoint address="net.msmq://localhost/private/wcfmsmq" binding="netMsmqBinding"

              bindingConfiguration="netMsmq" contract="RecoveryService.IRecoveryService"

              name="netMsmqRecoveryService" />

  </client>

</system.serviceModel>

If you tried to run your project with IIS Express and call the msmq service, you will hit with this error "The protocol 'net.msmq' is not supported.". This is because IIS Express does not support net.pipe protocol. You need to host them to your IIS. For more detail about IIS Express, you can check out from the following link http://www.iis.net/learn/extensions/introduction-to-iis-express/iis-express-faq.

When deploying your msmq service to IIS, make sure that your web site contain the net.msmq binding and the Enabled Protocols contains net.msmq. Otherwise you will get hit with the error message "The protocol 'net.msmq' is not supported."

To simplify the implementation to call msmq service, add a service reference (in this case is RecoveryService) to your project. Then call the service's method and the data will be sent to msmq. If you noticed that the data is in the queue and did not get process, this is due to your msmq service is not active. Just invoke the msmq service url and it will become active and process the queue message.

[C#]

var proxy = new RecoveryServiceClient();

try

{

    proxy.Log(value);

}

finally

{

    proxy.Close();

}

[VB]

Dim proxy As RecoveryServiceClient = New RecoveryServiceClient()

Try

    proxy.Log(value)

Catch ex As Exception

    proxy.Close()

End Try

For the binding value configured in netMsmqBinding section in the sample configuration defined above:
maxReceivedMessageSize - To specify how large the data is allowed to be sent through WCF service,
maxRetryCycles - Define the number of times to try before performing the action specified at receiveErrorHandling attribute,
retryCycleDelay - The amount of waiting time before performing the next retry,
receiveErrorHandling - The action to be done after reached the maximum number of retry as specified in maxRetryCycles attribute.
For more details on what other attributes can be configured to the netMsmqBinding section can be found here https://msdn.microsoft.com/en-us/library/ms731380(v=vs.110).aspx.

So, based on the values specified, if the method fail to process, it will place the data back to the queue and wait for 5 seconds before trying to process the data again. After retried for 3 times, which is the maximum number of retry as configured, MSMQ will remove the data from the queue. The reason why it is being removed from the queue is because Drop is specified in the receiveErrorHandling attribute.

If you do not want the message to be removed from the queue after reached the maximum number of retry attempt, you can consider moving the poison message to the sub-queue by assigning value Move to the receiveErrorHandling attribute.

For more details on handling poison message or to move them into poison message sub-queue and handle the message in the sub-queue, you can refer to https://msdn.microsoft.com/en-us/library/aa395218(v=vs.110).aspx.

Here's the sample code that are developed in layered by following http://serena-yeoh.blogspot.com/2014/03/layered-architecture-solution-guidance.html: C#: https://onedrive.live.com/redir?resid=E6612168B803803D!356&authkey=!AESnIsw8nRxITpY&ithint=file%2czip
VB: https://onedrive.live.com/redir?resid=E6612168B803803D!357&authkey=!AHKlSmIMOkYn-nQ&ithint=file%2czip

Read further if you want to run the sample project.

To run the sample, create a transactional msmq with the name wcfmsmq and publish the project that ends with Hosts.Web to your IIS, since IIS Express does not support net.msmq protocol.

To call the method to send data to MSMQ with WCF Service, you can either call it using the WCFTestClient application or run the project that ends with UI.Web and hit the button that displayed on the page. Do make sure to change the endpoint address in the configuration file located in the project that ends with UI.Web and point it to the project that you had published to IIS before hitting on the button.

Once you hit the button, it will assume that the method had failed and send the data to the queue. To simulate the retry mechanism until the MSMQ drop the data from the queue, the method that handles the MSMQ data will check for the text file existence and throw exception if is doesn't exist.

If you want the queue to process the data successfully, change the appSettings' logPath in the hosts.web to your desired location and create a folder name "SampleLog" with the extension ".txt". Or if you prefer to have your own implementation, just change the method "Log" implementation to your desired behavior in the RecoveryComponent file.

Creating zip file with ZipArchive in C# & VB

It is common for us to develop a function to compress physical files or any content generated from our code into zip archives. To implement the functionality, we may opt to use third party libraries to do so. If your project can target .NET Framework 4.5 and above, then you are able to use ZipArchive for file(s) or content compression.

Here are some stuff that ZipArchive can do:
1. Compress 1 or more files into a new or existing zip file.
2. The name of the file(s) can be changed before compress it to the zip file.
3. Compress content generated in codes, specify the file for the content to be stored into zip file.
4. Delete 1 or more files in the zip file.
5. Extract files.
6. 3 levels from compression (Fastest, Optimal, NoCompression).
7. Compress content or files into stream.

Without further ado, Let us check out how to use the ZipArchive. To use the ZipArchive, you need to have the following references. If you want to do more with ZipArchive, you need to have a reference to the System.IO.Compression.FileSystem namespace.

[C#]

using System.IO.Compression;

[VB]

Imports System.IO.Compression

Next is to initialize the ZipArchive.

• archiveFileName: The location of the zip file.
• mode: Action to be taken to the zip file. 
• 3 Modes
• Create : For creating a new zip file.
• Read : For accessing the zip file content.
• Update: For changing the zip file content.

[C#]

var zipArchive = ZipFile.Open(archiveFileName, mode);

[VB]

Dim zipArchive As ZipArchive = ZipFile.Open(archiveFileName, mode)

After initializing the ZipArchive, you can start compressing, deleting or extracting files. Let's start with extracting files. By executing the following code, all the files in the zip will be extracted and placed in a folder. The location of the folder is based on what you specified in the parameter.

• destinationDirectoryName: Define the location for extracting the content in the zip file.

[C#]

zipArchive.ExtractToDirectory(destinationDirectoryName);

[VB]

zipArchive.ExtractToDirectory(destinationDirectoryName)

For the following code, it is used to compress physical file into the zip file.

• sourceFileName: The physical file location. 
• entryName: The name of the physical file when compress it to zip file. 
• compressionLevel: Define the CompressionLevel of the file. 
• 3 CompressionLevel 
• Fastest: Compress the file quickly.
• Optimal: Compress the file optimally.
• NoCompression: No compression done on the file.

[C#]

zipArchive.CreateEntryFromFile(sourceFileName, entryName, compressionLevel);

[VB]

zipArchive.CreateEntryFromFile(sourceFileName, entryName, compressionLevel)

And finally, the following code is to remove the file located inside the zip file.

• entryName: The name of the file located in the zip file.

[C#]

var zipArchiveEntry = zipArchive.GetEntry(entryName);

zipArchiveEntry.Delete();

[VB]

Dim zipArchiveEntry As ZipArchiveEntry = zipArchive.GetEntry(entryName)

zipArchiveEntry.Delete()

If you want to compress files or content into a stream or stream the compressed content through WCF, you can do so with ZipArchive. Other than that, please remember to dispose of any disposable objects after you have finished using them, this is to prevent any memory leak from happening. You can dispose them by calling the .Dispose() method or use the using statement.

For more details on how to use ZipArchive and how to use stream with ZipArchive, you can check out the sample project here. https://1drv.ms/u/s!Aj2AA7hoIWHmgnaTDEvJCLxcXVtt

Thread Synchronization with SpinLock and How to Implement it in C# & VB

Ever face a situation where you need to access a value concurrently and prevent race condition from happening. For your application that deals with multiple threads and every threads needs to have exclusive right to change the value, there are a few kinds of lock that can be used. For more details on the list of available locks, you can refer to the following link https://msdn.microsoft.com/en-us/library/ms228964(v=vs.110).aspx

For now we will look into SpinLock. What Spinlock does is that if thread [A] has attain the lock, other threads will just wait for the thread [A] to release the lock. While waiting for the thread [A] to release the lock, the spinlock will just spin in the loop until the lock is being release by the thread [A].

Due to this, SpinLock is only suitable if the lock is being held in a very short duration. Acquiring the lock for a long duration will reduce the performance of other applications since more CPU cycles is being used. Also, it is a waste of CPU time to held the lock for a long duration, since it basically just do nothing other than loop until the lock is available.

So, before we look into how to use SpinLock, make sure your project is targeting .NET Framework version 4 and above.

Implementing SpinLock is pretty easy and straight forward. Firstly, you need to have an instance of SpinLock to get started.

[C#]

SpinLock spinLock = new SpinLock();

[VB]

Dim spinLock As SpinLock = New SpinLock()

The isLocked variable, which is a boolean variable, is to define whether the thread owns the lock. isLocked variable needs to be declared as a local variable, so that the value don't get overwrite by other threads.

[C#]

bool isLocked = false;

[VB]

Dim isLocked As Boolean = False

spinlock.Enter is to acquire the lock and wait for the lock to be released if is owned by other thread.

[C#]

spinLock.Enter(ref isLocked);

[VB]

spinLock.Enter(isLocked)

spinlock.Exit is to release the lock and to enable other threads to acquire the lock.

[C#]

spinLock.Exit();

[VB]

spinLock.Exit()

So let's take an example where you would like to have a multiple threads accessing a value from a variable and at the same time need to ensure that race condition did not happen. To prove that race condition did not happen with SpinLock, I have created a simple sample in a console to demonstrate this. Assuming the following method is to increase the value of an integer. To prevent other threads from accessing the variable _valueWithLock, the method is being implemented it with SpinLock.

[C#]

private static void ChangeValueWithSpinLock()

{

    var isLocked = false;

    try

    {

        _spinLock.Enter(ref isLocked);

        _valueWithLock++;

    }

    finally

    {

        if (isLocked)

        {

            _spinLock.Exit();

        }

    }

}

[VB]

Private Sub ChangeValueWithSpinLock()

    Dim isLocked As Boolean = False

    Try

        _spinLock.Enter(isLocked)

        _valueWithLock += 1

    Finally

        If isLocked Then

            _spinLock.Exit()

        End If

    End Try

End Sub

To simulate multiple threads accessing the method, a Parallel class is being used. It will loop and call the methods 1000000 times.

[C#]

Parallel.For(0, 1000000, (i) => {

    ChangeValue();

});

[VB]

Parallel.For(0, 1000000, New Action(Of Integer)(Sub()

                                                    ChangeValue()

                                                End Sub))

By running the codes, you will notice that the value will increase to 1000000. Which means no race condition occurred. 

The sample project can be obtained here. https://1drv.ms/u/s!Aj2AA7hoIWHmgmKoweIKoaf5z9hf