80 lines
2.6 KiB
Markdown
80 lines
2.6 KiB
Markdown
---
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layout: post
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title: A Handy C# Async Utility Method
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author: Daniel
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date: 2014-08-04 19:48:43
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categories:
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- [ Programming, .NET, C# ]
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tags:
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- asynchronous
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- c#
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- utility
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summary: Using async when you can't use async
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---
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In the course of writing C# code utilizing the new (for 4.5.1) [Task-based asynchronous programming][async], I've run across a couple of places where the `await` keyword either is not allowed (a catch block or a property accessor) or the `async` keyword greatly complicates the syntax (lambda expressions). I've found myself writing this method for two different projects, and so I thought I would drop this Q&D, more-comments-than-code utility method here for others to use if you see the need.
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_(UPDATE: This works well in console applications; it can cause deadlocks in desktop and web apps. Test before you rely on it.)_
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{% codeblock lang:csharp %}
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/// <summary>
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/// Get the result of a task in contexts where the "await" keyword may be prohibited
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/// </summary>
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/// <typeparam name="T">The return type for the task</typeparam>
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/// <param name="task">The task to be awaited</param>
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/// <returns>The result of the task</returns>
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public static T TaskResult<T>(Task<T> task)
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{
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Task.WaitAll(task);
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return task.Result;
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}
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{% endcodeblock %}
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And, in places where you can't do something like this...
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{% codeblock ExampleClass.cs lang:csharp %}
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/// <summary>
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/// A horribly contrived example class
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/// </summary>
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/// <remarks>Don't ever structure your POCOs this way, unless EF is handling the navigation properties</remarks>
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public class ExampleClass
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{
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/// <summary>
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/// A contrived ID to a dependent entity
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/// </summary>
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public int ForeignKeyID { get; set; }
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/// <summary>
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/// The contrived dependent entity
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/// </summary>
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public DependentEntity DependentEntity
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{
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get
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{
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// Does not compile; can't use await without async, can't mark a property as async
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return await Data.DependentEntities
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.FirstOrDefaultAsync(entity => entity.ID == ForeignKeyID);
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}
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}
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}
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{% endcodeblock %}
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...you can instead do this in that "DependentEntity" property...
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{% codeblock lang:csharp %}
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/// <summary>
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/// The contrived dependent entity
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/// </summary>
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public DependentEntity DependentEntity
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{
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get
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{
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return UtilClass.TaskResult<DependentEntity>(Data.DependentEntities
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.FirstOrDefaultAsync(entity => entity.ID == ForeignKeyID));
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}
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}
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{% endcodeblock %}
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[async]: //msdn.microsoft.com/EN-US/library/hh191443(v=vs.110).aspx "Asynchronous Programming with Async and Await - MSDN"
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