WP7: change border background with converter

Question

I'm going crazy with converters. I know that I should use it to change the "output" value of my values ​​when necessary, but I do not know how to use it correctly for my case.

I have my simple MVVM (only 3 fields) and my main window with a list of my elements. The first element is calculated depending on the function and can show YES or NOT, other values ​​are bound directly.

This works well, but I need to change the background and foreground color depending on the YES or NOT value that I have in the first calculated field. For instance:

YES (must be blue) - ITEM 1
NO (must be grey)  - ITEM 2
YES (must be blue) - ITEM 3

While the internal values ​​in my database (in this case, the calculation is a module):

2 - ITEM 1
3 - ITEM 2
4 - ITEM 3

My ListBox code is this:

<phone:PhoneApplicationPage 
x:Class="Pasti.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
shell:SystemTray.IsVisible="True">

<Grid x:Name="LayoutRoot" Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>

    <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
        <TextBlock Text="My App" Style="{StaticResource PhoneTextNormalStyle}" />
        <TextBlock Text="My List" Style="{StaticResource PhoneTextTitle1Style}" />
    </StackPanel>

<ListBox x:Name="lstPills" Grid.Row="1" ItemsSource="{Binding AllItems}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <Grid HorizontalAlignment="Stretch" Width="440">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="90" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Border Background="HERE MUST GO THE CONVERTER, I SUPOSE">
                    <TextBlock Text="{Binding IsPair, Mode=TwoWay}"/>
                </Border>
                <TextBlock
                    Text="{Binding Name}"
                    FontSize="{StaticResource PhoneFontSizeLarge}"
                    Grid.Column="1"
                    VerticalAlignment="Center"/>
            </Grid>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>
</Grid>
</phone:PhoneApplicationPage>

And the CS code for this page:

public partial class MainPage : PhoneApplicationPage
{
    // Constructor
    public MainPage()
    {
        InitializeComponent();

        // Set the page DataContext property to the ViewModel.
        this.DataContext = App.ViewModel;
    }
}

(_myNumber , ):

    // Define a custom field based on some database values
    // Get is calculated, while set will force it to refresh by Notifying
    public string IsPair
    {
        get
        {
            return _myNumber % 2 == 0 ? "YES" : "NO";
        }
        set
        {
            NotifyPropertyChanged("IsPair");
        }
    }

. , set TwoWay, IsPair = "", , . , .

, , , , IsPair, Background Border to Blue Gray? , , .

, MainPage.cs, MainPage, - :

// Converter for the YES-NO column on the list
public class IsPairConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (MY_CALCULATED_VALUE == "YES")
            return "Blue";

        return "Grey";
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

MY_CALCULATED_VALUE Background ?

Answer 1

!

IsPair :

<Border Background="{Binding IsPair, Converter={StaticResource IsPairConverter}}">
    <TextBlock Text="{Binding IsPair, Mode=TwoWay}"/>
</Border>

:

public class IsPairConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        // You might want to add additional checks for type safety
        var calculatedValue = (string)value; 

        var color = calculatedValue == "YES" ? Colors.Blue : Colors.Gray;

        return new SolidColorBrush { Color = color };
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

.

---

, , , IsPair, MyNumber IsPair:

private int myNumber;

public string IsPair { get; protected set; }

protected int MyNumber
{
    get
    {
        return this.myNumber;
    }

    set
    {
        this.myNumber = value;
        this.IsPair = value % 2 == 0 ? "YES" : "NO";
        this.NotifyPropertyChanged("IsPair");
    }
}