/
NullChangeToken.cs
44 lines (38 loc) · 1.36 KB
/
NullChangeToken.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using Microsoft.Extensions.Primitives;
namespace Microsoft.Extensions.FileProviders
{
/// <summary>
/// An empty change token that doesn't raise any change callbacks.
/// </summary>
public class NullChangeToken : IChangeToken
{
/// <summary>
/// A singleton instance of <see cref="NullChangeToken"/>
/// </summary>
public static NullChangeToken Singleton { get; } = new NullChangeToken();
private NullChangeToken()
{
}
/// <summary>
/// Always false.
/// </summary>
public bool HasChanged => false;
/// <summary>
/// Always false.
/// </summary>
public bool ActiveChangeCallbacks => false;
/// <summary>
/// Always returns an empty disposable object. Callbacks will never be called.
/// </summary>
/// <param name="callback">This parameter is ignored</param>
/// <param name="state">This parameter is ignored</param>
/// <returns>A disposable object that noops on dispose.</returns>
public IDisposable RegisterChangeCallback(Action<object?> callback, object? state)
{
return EmptyDisposable.Instance;
}
}
}