89 строки
2.6 KiB
C#
89 строки
2.6 KiB
C#
//
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// AsyncValue.cs
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//
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// Author:
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// Eric Maupin <me@ermau.com>
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//
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// Copyright (c) 2013-2014 Xamarin, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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using System;
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using System.ComponentModel;
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using System.Runtime.CompilerServices;
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using System.Threading;
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using System.Threading.Tasks;
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namespace Xamarin.Forms.Platform.WinPhone
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{
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internal sealed class AsyncValue<T> : INotifyPropertyChanged
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{
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readonly T _defaultValue;
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readonly Task<T> _valueTask;
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bool _isRunning = true;
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public AsyncValue(Task<T> valueTask, T defaultValue)
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{
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if (valueTask == null)
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throw new ArgumentNullException("valueTask");
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_valueTask = valueTask;
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_defaultValue = defaultValue;
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TaskScheduler scheduler = TaskScheduler.FromCurrentSynchronizationContext();
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_valueTask.ContinueWith(t => { IsRunning = false; }, scheduler);
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_valueTask.ContinueWith(t => { OnPropertyChanged("Value"); }, CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
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}
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public bool IsRunning
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{
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get { return _isRunning; }
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set
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{
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if (_isRunning == value)
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return;
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_isRunning = value;
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OnPropertyChanged();
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}
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}
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public T Value
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{
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get
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{
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if (_valueTask.Status != TaskStatus.RanToCompletion)
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return _defaultValue;
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return _valueTask.Result;
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}
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}
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public event PropertyChangedEventHandler PropertyChanged;
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void OnPropertyChanged([CallerMemberName] string propertyName = null)
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{
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PropertyChangedEventHandler handler = PropertyChanged;
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if (handler != null)
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handler(this, new PropertyChangedEventArgs(propertyName));
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}
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}
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} |