80 lines
2.6 KiB
Markdown
80 lines
2.6 KiB
Markdown
|
---
|
||
|
|
layout: post
|
||
|
|
title: A Handy C# Async Utility Method
|
||
|
|
author: Daniel
|
||
|
|
date: 2014-08-04 19:48:43
|
||
|
|
categories:
|
||
|
|
- [ Programming, .NET, C# ]
|
||
|
|
tags:
|
||
|
|
- asynchronous
|
||
|
|
- c#
|
||
|
|
- utility
|
||
|
|
summary: Using async when you can't use async
|
||
|
|
---
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
_(UPDATE: This works well in console applications; it can cause deadlocks in desktop and web apps. Test before you rely on it.)_
|
||
|
|
|
||
|
|
{% codeblock lang:csharp %}
|
||
|
|
/// <summary>
|
||
|
|
/// Get the result of a task in contexts where the "await" keyword may be prohibited
|
||
|
|
/// </summary>
|
||
|
|
/// <typeparam name="T">The return type for the task</typeparam>
|
||
|
|
/// <param name="task">The task to be awaited</param>
|
||
|
|
/// <returns>The result of the task</returns>
|
||
|
|
public static T TaskResult<T>(Task<T> task)
|
||
|
|
{
|
||
|
|
Task.WaitAll(task);
|
||
|
|
return task.Result;
|
||
|
|
}
|
||
|
|
{% endcodeblock %}
|
||
|
|
|
||
|
|
And, in places where you can't do something like this...
|
||
|
|
|
||
|
|
{% codeblock ExampleClass.cs lang:csharp %}
|
||
|
|
/// <summary>
|
||
|
|
/// A horribly contrived example class
|
||
|
|
/// </summary>
|
||
|
|
/// <remarks>Don't ever structure your POCOs this way, unless EF is handling the navigation properties</remarks>
|
||
|
|
public class ExampleClass
|
||
|
|
{
|
||
|
|
/// <summary>
|
||
|
|
/// A contrived ID to a dependent entity
|
||
|
|
/// </summary>
|
||
|
|
public int ForeignKeyID { get; set; }
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// The contrived dependent entity
|
||
|
|
/// </summary>
|
||
|
|
public DependentEntity DependentEntity
|
||
|
|
{
|
||
|
|
get
|
||
|
|
{
|
||
|
|
// Does not compile; can't use await without async, can't mark a property as async
|
||
|
|
return await Data.DependentEntities
|
||
|
|
.FirstOrDefaultAsync(entity => entity.ID == ForeignKeyID);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
{% endcodeblock %}
|
||
|
|
|
||
|
|
...you can instead do this in that "DependentEntity" property...
|
||
|
|
|
||
|
|
{% codeblock lang:csharp %}
|
||
|
|
/// <summary>
|
||
|
|
/// The contrived dependent entity
|
||
|
|
/// </summary>
|
||
|
|
public DependentEntity DependentEntity
|
||
|
|
{
|
||
|
|
get
|
||
|
|
{
|
||
|
|
return UtilClass.TaskResult<DependentEntity>(Data.DependentEntities
|
||
|
|
.FirstOrDefaultAsync(entity => entity.ID == ForeignKeyID));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
{% endcodeblock %}
|
||
|
|
|
||
|
|
|
||
|
|
[async]: //msdn.microsoft.com/EN-US/library/vstudio/hh191443(v=vs.110).aspx "Asynchronous Programming with Async and Await - MSDN"
|