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Posts Tagged ‘Localization’

Format WPF Bindings With Resource File Lookups

March 21st, 2009
3 comments

This post explains a pattern that combines Data Binding, the new StringFormat property and resource lookups through the application of a custom MarkupExtension.

 

StringFormat

Microsoft introduced the StringFormat property with SP1 for .NET 3.5. StringFormat often eliminates the need for a custom converter if you just need to format a bound value.
Here’s a very simple sample that displays hello xxx on the screen (where “xxx” is the value entered in a TextBox control:

 

<TextBox
    x:Name="name"
    Text="world" />

<TextBlock
    Text="{Binding ElementName=name,
                   Path=Text,
                   StringFormat=hello {0}}" />

 

Resource Files

I often use resource files to store strings – not only for localization tasks but also in order to maintain strings that are intended for users at a central place. My resource strings often contain placeholders which are populated at runtime using String.Format:

 

image

 

//use resource file to create message
var msg = Resources.Ask_Whether_To_Connect_To_New_Share;
msg = String.Format(msg, configuration.Name);

//display dialog
MessageBoxResult doConnect = Dialogs.ShowYesNo(msg);

 

 

Bringing Bindings and Resource Files Together

In the sample above, I accessed the resource file programmatically. In XAML however, I prefer a declarative approach. In order to get there, I implemented a simple MarkupExtension that allows me to do just that:

 

<!-- Display a formatted text -->
<TextBlock
  x:Name="Title"
  Text="{Binding Path=Name,
                 StringFormat={ext:Resource Ask_Whether_To_Connect_To_New_Share}}"
 />

 

The above snippet results in a formatted text being displayed:

image

 

Resource MarkupExtension

Here’s the markup extension. As you can see, it’s fairly trivial. Do note that the reference to the application’s Resources file is hardcoded – you will have to set a using statement or adjust that line in order to use your custom resource file.

 

/// <summary>
/// A markup extension that provides simple access to a given
/// entry in the application's <see cref="Resources"/> file.
/// </summary>
public class Resource : MarkupExtension
{
  /// <summary>
  /// The resource key to be used for the lookup.
  /// </summary>
  public string ResourceKey { get; set; }


  /// <summary>
  /// Inits the <see cref="Resource"/> markup extension
  /// with the key to be assigned.
  /// </summary>
  /// <param name="resourceKey">The resource key to be assigned.</param>
  public Resource(string resourceKey)
  {
    ResourceKey = resourceKey;
  }


  /// <summary>
  /// Performs a lookup for the defined <see cref="ResourceKey"/>.
  /// </summary>
  /// <returns>
  /// The value of the resource that is specified by the
  /// <see cref="ResourceKey"/> property. If the property is not
  /// set, a null reference is returned.
  /// </returns>
  public override object ProvideValue(IServiceProvider serviceProvider)
  {
    if (String.IsNullOrEmpty(ResourceKey)) return null;
    return Resources.ResourceManager.GetObject(ResourceKey);
  }
}

 

Enjoy 🙂

Author: Categories: WPF Tags: ,