NullableBoolExtension.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

namespace CommunityToolkit.WinUI;

/// <summary>
/// Custom <see cref="MarkupExtension"/> which can provide nullable bool values.
/// See https://wpdev.uservoice.com/forums/110705-universal-windows-platform/suggestions/17767198-nullable-dependency-properties.
/// </summary>
[MarkupExtensionReturnType(ReturnType = typeof(bool?))]
public partial class NullableBoolExtension : MarkupExtension
{
    /// <summary>
    /// Gets or sets a value indicating whether the value of the Boolean is true.  Ignored if <see cref="IsNull"/> is true.
    /// </summary>
    public bool Value { get; set; }

    /// <summary>
    /// Gets or sets a value indicating whether the value should be null.  Overrides the <see cref="Value"/> property.
    /// </summary>
    public bool IsNull { get; set; }

    /// <inheritdoc/>
    protected override object? ProvideValue()
    {
        if (IsNull)
        {
            return null;
        }

        return Value;
    }
}