DevCorner

Silverlight Quick Tip: Dynamically Updating Class Fields/Properties

In previous post (here) I blogged about displaying values of class/control in runtime and displaying them in Visual Studio - like property window. Today I’ll show how to push them back to the class instance.

In previous post I’ve stored values in “ObservableCollection<FieldsPropertiesData>” for easy databinding and connected this ListBox control. In order to get user input I’ve created TwoWay databinding in DataTemplate – here is updated data template:

<Style TargetType="local:FiledPropertyData">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="local:FiledPropertyData">
        <Grid ToolTipService.Placement="Mouse" Width="{TemplateBinding Width}">
          <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
          </Grid.ColumnDefinitions>
          <TextBlock Text="{Binding DisplayName}" VerticalAlignment="Center" HorizontalAlignment="Left" Margin="0,0,10,0"/>
          <TextBox Text="{Binding FieldValue, Mode=TwoWay}" VerticalAlignment="Center" HorizontalAlignment="Right" 
                   IsEnabled="{Binding IsReadOnly, Converter={StaticResource boolToEnabledConverter}}" Grid.Column="1"/>
          <ToolTipService.ToolTip>
            <ToolTip Background="Transparent" BorderBrush="Transparent" BorderThickness="0" Padding="0" Margin="5">
              <ToolTip.Content>
                <Border Background="PaleGoldenrod" BorderBrush="Black" BorderThickness="2" CornerRadius="5" Padding="5" Margin="0">
                  <TextBlock Text="{Binding Description}"/>
                </Border>
              </ToolTip.Content>
            </ToolTip>
          </ToolTipService.ToolTip>
        </Grid>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

Now at the setter of the “FieldValue” property all I need is to push it back to the instance.

I’ve create function, which accepts FieldName, FieldType (from data already exits in the file from the loading) and new value:

private static void SetFieldValue(string FieldName, Type FieldType, object TheValue)
{
  Assembly asm = Assembly.GetExecutingAssembly();
  Type type = asm.GetType("SAMPLE_TYPE_TO_UPDATE");
  FieldInfo[] fields = type.GetFields(BindingFlags.Static | BindingFlags.Instance | BindingFlags.Public);

  var fieldInfo = from field in fields
                  where field.FieldType == FieldType && field.Name == FieldName
                  select field;

  FieldInfo theField = fieldInfo.FirstOrDefault();
  if (null != theField)
    if (value.GetType() == FieldType)
      theField.SetValue(if (theField.IsStatic) ? null : TheInstance, TheValue);
    else //In case of value changed by databinding in most cases ToString() result will be here, 
         //hence need to convert
      theField.SetValue(if (theField.IsStatic) ? null : TheInstance, Convert.ChangeType(TheValue, FieldType, null));

  fieldInfo = null;
  fields = null;
  type = null;
  asm = null;
}

That’s it… Now the data dynamically displayed, updated by user and pushed back to the instance of the object.

Enjoy,

Alex