Converters basically provides a translation between your binding source and destination.

Generally we use single level converters like (Bool to Visibility Converter), (Color to Brush Converter), (Enum to Bool converter) and list is endless..

Now consider a scenario in which we require Multi-level conversion i.e from A => B => C.

Lets take an example, Suppose we have Bool to Visibility Converter and Color to Bool converter, and we want a translation like Color to Visibility Conversion.

So instead of making Color To Visibility converter we can make some generic converter that allows us to do multilevel Conversion.

Below is the Code of that Multi level Converter

public class ValueConverterGroup : IValueConverter
  {
    #region Data
    /// <summary>
    /// Stores the list of values, on which the converter has to be applied.
    /// </summary>
    private readonly ObservableCollection<IValueConverter> converters = new ObservableCollection<IValueConverter>();

    /// <summary>
    /// Stores the dictionary, mapping of value with its conversion attribute.
    /// </summary>
    private readonly Dictionary<IValueConverter, ValueConversionAttribute> cachedAttributes = new Dictionary<IValueConverter, ValueConversionAttribute>();

    #endregion

    #region Constructor
    /// <summary>
    /// 
    /// </summary>
    public ValueConverterGroup()
    {
      this.converters.CollectionChanged += this.OnConvertersCollectionChanged;
    }

    #endregion

    #region Converters

    /// <summary>
    /// Returns the list of IValueConverters contained in this converter.
    /// </summary>
    public ObservableCollection<IValueConverter> Converters
    {
      get { return this.converters; }
    }

    #endregion

    #region IValueConverter Members

    object IValueConverter.Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
      object output = value;

      for (int i = 0; i < this.Converters.Count; ++i)
      {
        IValueConverter converter = this.Converters[i];
        Type currentTargetType = this.GetTargetType(i, targetType, true);
        output = converter.Convert(output, currentTargetType, parameter, culture);

        // If the converter returns 'DoNothing' then the binding operation should terminate.
        if (output == Binding.DoNothing)
          break;
      }

      return output;
    }

    object IValueConverter.ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
      object output = value;

      for (int i = this.Converters.Count - 1; i > -1; --i)
      {
        IValueConverter converter = this.Converters[i];
        Type currentTargetType = this.GetTargetType(i, targetType, false);
        output = converter.ConvertBack(output, currentTargetType, parameter, culture);

        // When a converter returns 'DoNothing' the binding operation should terminate.
        if (output == Binding.DoNothing)
          break;
      }

      return output;
    }

    #endregion

    #region Private Helpers

    #region GetTargetType

    /// <summary>
    /// Returns the target type for a conversion operation.
    /// </summary>
    protected virtual Type GetTargetType(int converterIndex, Type finalTargetType, bool convert)
    {
      // If the current converter is not the last/first in the list, 
      // get a reference to the next/previous converter.
      IValueConverter nextConverter = null;
      if (convert)
      {
        if (converterIndex < this.Converters.Count - 1)
        {
          nextConverter = this.Converters[converterIndex + 1];
          if (nextConverter == null)
            throw new InvalidOperationException("The Converters collection of the ValueConverterGroup contains a null reference at index: " + (converterIndex + 1));
        }
      }
      else
      {
        if (converterIndex > 0)
        {
          nextConverter = this.Converters[converterIndex - 1];
          if (nextConverter == null)
            throw new InvalidOperationException("The Converters collection of the ValueConverterGroup contains a null reference at index: " + (converterIndex - 1));
        }
      }

      if (nextConverter != null)
      {
        ValueConversionAttribute conversionAttribute = cachedAttributes[nextConverter];

        // If the Convert method is going to be called, we need to use the SourceType of the next 
        // converter in the list.  If ConvertBack is called, use the TargetType.
        return convert ? conversionAttribute.SourceType : conversionAttribute.TargetType;
      }

      // If the current converter is the last one to be executed return the target type passed into the conversion method.
      return finalTargetType;
    }

    #endregion // GetTargetType

    #region OnConvertersCollectionChanged

    void OnConvertersCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
      // The 'Converters' collection has been modified, so validate that each value converter it now
      // contains is decorated with ValueConversionAttribute and then cache the attribute value.

      IList convertersToProcess = null;
      if (e.Action == NotifyCollectionChangedAction.Add ||
        e.Action == NotifyCollectionChangedAction.Replace)
      {
        convertersToProcess = e.NewItems;
      }
      else if (e.Action == NotifyCollectionChangedAction.Remove)
      {
        foreach (IValueConverter converter in e.OldItems)
          this.cachedAttributes.Remove(converter);
      }
      else if (e.Action == NotifyCollectionChangedAction.Reset)
      {
        this.cachedAttributes.Clear();
        convertersToProcess = this.converters;
      }

      if (convertersToProcess != null && convertersToProcess.Count > 0)
      {
        foreach (IValueConverter converter in convertersToProcess)
        {
          object[] attributes = converter.GetType().GetCustomAttributes(typeof(ValueConversionAttribute), false);

          if (attributes.Length != 1)
            throw new InvalidOperationException("All value converters added to a ValueConverterGroup must be decorated with the ValueConversionAttribute attribute exactly once.");

          this.cachedAttributes.Add(converter, attributes[0] as ValueConversionAttribute);
        }
      }
    }
    #endregion
    #endregion
  }

And in Xaml simply define your Converters in a required order, like

<convert:ValueConverterGroup x:Key="colorToVisibilityConverter">
        <convert:ColorToBooleanConverter />
        <convert:BooleanToVisibilityConverter />
      </convert:ValueConverterGroup>

 and thats all. You can have n levels of conversion A => B => C => D.....N levels

In this article, I am going to describe how to create your own custom configuration section in Asp.net and how to use it, in a few very simple steps.

Step 1: Create a public class which you want to refer as the class that is holding up the config section, give it some name which shows its stores some kind of setting lets say “UserSettings” and make the class inherited by ConfigurationSection

public class UserSettings : ConfigurationSection

Step 2: Create some properties in this class which have the “ConfigurationProperty” Attribute in this manner

[ConfigurationProperty("MyVariable1", IsRequired = true)]
public string MyVariable1
{
    get { return (string)this["MyVariable1"]; }
    set { this["MyVariable1"] = value; }
}

Lets create three such test properties and then this is how the class looks like

public class UserSettings : ConfigurationSection {
    [ConfigurationProperty("MyVariable1", IsRequired = true)]
    public string MyVariable1
    {
        get { return (string)this["MyVariable1"]; }
        set { this["MyVariable1"] = value; }
    }

    [ConfigurationProperty("MyVariable2", IsRequired = true)]
    public string MyVariable2
    {
        get { return (string)this["MyVariable2"]; }
        set { this["MyVariable2"] = value; }
    }

    [ConfigurationProperty("MyVariable3", IsRequired = true)]
    public string MyVariable3
    {
        get { return (string)this["MyVariable3"]; }
        set { this["MyVariable3"] = value; }
    }
}

Step 3: Open the web.config file and define a Config Section under the tag <Configuration> like this,

<configSections> <section name="UserSettings"
     type="Example.Web.Utilities.UserSettings, Example.Web, Version=1.0.0.0, Culture=neutral" 
     allowLocation="true" allowDefinition="Everywhere" /> 
</configSections>

Now this is the information about the library that gets created when you “Build”

next step, we tell the config section what “UserSettings” is,

<UserSettings
     MyVariable1="Value1"
     MyVariable2="Value2"
     MyVariable3="Value3" />

and altogether it looks like this

<configuration> 
     <configSections>
          <section name="UserSettings" type="Example.Web.Utilities.UserSettings, Example.Web, Version=1.0.0.0, Culture=neutral"  allowLocation="true" allowDefinition="Everywhere" />
     </configSections>
     <UserSettings 
           MyVariable1="Value1"
           MyVariable2="Value2"
           MyVariable3="Value3" /> 
     <system.web>
           <compilation debug="true" targetFramework="4.0" />
     </system.web>
</configuration>

Step 4: We go to the code behind of the default page of project and fetch the settings

public class Default : Page 
{
        protected void Page_Load(object sender, EventArgs e)
        {
            var userSettings = ConfigurationManager.GetSection("UserSettings") as UserSettings;
            if(userSettings == null) return;

            Response.Write(
                "MyVariable1 = " + userSettings.MyVariable1 + "</br>" +
                "MyVariable2 = " + userSettings.MyVariable2 + "</br>" +
                "MyVariable3 = " + userSettings.MyVariable3 + "</br>");
        }
}

Next, I go run the application and get this

I have attached the sample project that we created through this post.

ConfigSectionExample.zip (6.58 kb)