104 строки
3.7 KiB
C#
104 строки
3.7 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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#pragma warning disable SA1512
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// This file is inspired from the MvvmLight library (lbugnion/MvvmLight),
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// more info in ThirdPartyNotices.txt in the root of the project.
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using System;
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using System.Runtime.CompilerServices;
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namespace CommunityToolkit.Mvvm.Input
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{
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/// <summary>
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/// A generic command whose sole purpose is to relay its functionality to other
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/// objects by invoking delegates. The default return value for the CanExecute
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/// method is <see langword="true"/>. This class allows you to accept command parameters
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/// in the <see cref="Execute(T)"/> and <see cref="CanExecute(T)"/> callback methods.
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/// </summary>
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/// <typeparam name="T">The type of parameter being passed as input to the callbacks.</typeparam>
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public sealed class RelayCommand<T> : IRelayCommand<T>
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{
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/// <summary>
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/// The <see cref="Action"/> to invoke when <see cref="Execute(T)"/> is used.
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/// </summary>
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private readonly Action<T?> execute;
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/// <summary>
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/// The optional action to invoke when <see cref="CanExecute(T)"/> is used.
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/// </summary>
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private readonly Predicate<T?>? canExecute;
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/// <inheritdoc/>
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public event EventHandler? CanExecuteChanged;
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/// <summary>
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/// Initializes a new instance of the <see cref="RelayCommand{T}"/> class that can always execute.
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/// </summary>
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/// <param name="execute">The execution logic.</param>
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/// <remarks>
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/// Due to the fact that the <see cref="System.Windows.Input.ICommand"/> interface exposes methods that accept a
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/// nullable <see cref="object"/> parameter, it is recommended that if <typeparamref name="T"/> is a reference type,
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/// you should always declare it as nullable, and to always perform checks within <paramref name="execute"/>.
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/// </remarks>
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public RelayCommand(Action<T?> execute)
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{
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this.execute = execute;
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="RelayCommand{T}"/> class.
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/// </summary>
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/// <param name="execute">The execution logic.</param>
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/// <param name="canExecute">The execution status logic.</param>
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/// <remarks>See notes in <see cref="RelayCommand{T}(Action{T})"/>.</remarks>
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public RelayCommand(Action<T?> execute, Predicate<T?> canExecute)
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{
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this.execute = execute;
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this.canExecute = canExecute;
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}
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/// <inheritdoc/>
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public void NotifyCanExecuteChanged()
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{
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CanExecuteChanged?.Invoke(this, EventArgs.Empty);
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}
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/// <inheritdoc/>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public bool CanExecute(T? parameter)
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{
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return this.canExecute?.Invoke(parameter) != false;
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}
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/// <inheritdoc/>
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public bool CanExecute(object? parameter)
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{
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if (default(T) is not null &&
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parameter is null)
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{
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return false;
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}
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return CanExecute((T?)parameter);
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}
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/// <inheritdoc/>
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public void Execute(T? parameter)
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{
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if (CanExecute(parameter))
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{
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this.execute(parameter);
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}
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}
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/// <inheritdoc/>
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public void Execute(object? parameter)
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{
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Execute((T?)parameter);
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}
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}
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} |