advanced-data-binding

# WPF Advanced Data Binding

## 1. MultiBinding

`MultiBinding` is used to combine multiple source values into a single binding target.

### 1.1 Basic Pattern

```xml
<TextBlock>
    <TextBlock.Text>
        <MultiBinding StringFormat="{}{0} {1}">
            <Binding Path="FirstName"/>
            <Binding Path="LastName"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>
```

### 1.2 With IMultiValueConverter

```csharp
public sealed class FullNameConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values.Length < 2 ||
            values[0] is not string firstName ||
            values[1] is not string lastName)
        {
            return DependencyProperty.UnsetValue;
        }

        return $"{firstName} {lastName}";
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}
```

```xml
<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource FullNameConverter}">
            <Binding Path="FirstName"/>
            <Binding Path="LastName"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>
```

### 1.3 Boolean Logic with MultiBinding

```csharp
public sealed class AllTrueConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        return values.All(v => v is true);
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}
```

```xml
<!-- Enable button only when all conditions are true -->
<Button Content="Submit">
    <Button.IsEnabled>
        <MultiBinding Converter="{StaticResource AllTrueConverter}">
            <Binding Path="IsFormValid"/>
            <Binding Path="IsNotBusy"/>
            <Binding Path="Ha