// 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. // This file is inspired from the MvvmLight library (lbugnion/MvvmLight), // more info in ThirdPartyNotices.txt in the root of the project. using System; using System.Runtime.CompilerServices; namespace CommunityToolkit.Mvvm.Input; /// <summary> /// A command whose sole purpose is to relay its functionality to other /// objects by invoking delegates. The default return value for the <see cref="CanExecute"/> /// method is <see langword="true"/>. This type does not allow you to accept command parameters /// in the <see cref="Execute"/> and <see cref="CanExecute"/> callback methods. /// </summary> public sealed class RelayCommand : IRelayCommand { /// <summary> /// The <see cref="Action"/> to invoke when <see cref="Execute"/> is used. /// </summary> private readonly Action execute; /// <summary> /// The optional action to invoke when <see cref="CanExecute"/> is used. /// </summary> private readonly Func<bool>? canExecute; /// <inheritdoc/> public event EventHandler? CanExecuteChanged; /// <summary> /// Initializes a new instance of the <see cref="RelayCommand"/> class that can always execute. /// </summary> /// <param name="execute">The execution logic.</param> public RelayCommand(Action execute) { this.execute = execute; } /// <summary> /// Initializes a new instance of the <see cref="RelayCommand"/> class. /// </summary> /// <param name="execute">The execution logic.</param> /// <param name="canExecute">The execution status logic.</param> public RelayCommand(Action execute, Func<bool> canExecute) { this.execute = execute; this.canExecute = canExecute; } /// <inheritdoc/> public void NotifyCanExecuteChanged() { CanExecuteChanged?.Invoke(this, EventArgs.Empty); } /// <inheritdoc/> [MethodImpl(MethodImplOptions.AggressiveInlining)] public bool CanExecute(object? parameter) { return this.canExecute?.Invoke() != false; } /// <inheritdoc/> public void Execute(object? parameter) { if (CanExecute(parameter)) { this.execute(); } } }