[Proposal] Variable Multi-Value Converter

VariableMultiValueConverter

• Proposed
• Prototype
• Implementation
  • iOS Support
  • Android Support
  • macOS Support
  • Windows Support
• Unit Tests
• Sample
• Documentation:https://github.com/MicrosoftDocs/CommunityToolkit/pull/108

Summary

The VariableMultiValueConverter is a converter that allows users to convert multiple bool value bindings to a single bool. It does this by enabling them to specify whether All, Any, None or a specific number of values are true as specified in ConditionType. This is useful when combined with MultiBinding

Detailed Design

VariableMultiValueConverter.shared.cs

public class VariableMultiValueConverter : MultiValueConverterExtension, IMultiValueConverter
{
  public MultiBindingCondition ConditionType { get; set; }

  public int Count { get; set; }

  public object Convert(object[]? values, Type? targetType, object? parameter, CultureInfo? culture)
  {
	if (values == null || values.Length == 0)
		return false;

	var boolValues = values.OfType<bool>().ToArray();

	if (boolValues.Length != values.Length)
		return false;

	var count = boolValues.Count(v => v);

	return ConditionType switch
	{
		MultiBindingCondition.Any => count >= 1,
		MultiBindingCondition.None => count == 0,
		MultiBindingCondition.Exact => count == Count,
		MultiBindingCondition.GreaterThan => count > Count,
		MultiBindingCondition.LessThan => count < Count,
		_ => count == boolValues.Count(),
	};
  }

  public object[]? ConvertBack(object? value, Type[]? targetTypes, object? parameter, CultureInfo? culture)
  {
	if (value is not bool boolValue || targetTypes?.Any(t => !t.IsAssignableFrom(typeof(bool))) is true)
		return null;

	return boolValue ? targetTypes?.Select(t => ConditionType == MultiBindingCondition.All).OfType<object>().ToArray() : null;
  }
}

Usage Syntax

[bijington]

Done thanks @CliffAgius

[brminnick]

Thanks! Yea, GitHub has a weird quirk that we can’t assign an Issue to anyone who isn’t a maintainer or who hasn’t commented directly on the Issue 🤷‍♂️