如何在 C# 中只异步调用几个方法？

Question

我知道这个问题已经被问过很多次关于堆栈溢出的问题，但我正在寻找一些关于我下面代码的建议。
在我的应用程序中有许多难以修改的同步方法。我无法将所有内容更改为异步等待。但我想异步运行几个方法。 我为此写了一些代码。我还添加了有助于理解我的要求的 cmets。

这是我的代码：

    //This class will perform some heavy operation and also going to call an API for tax configuration.
    //The original class takes almost 2 sec to respond. Obviously we are refactoring it but also want this class methods to run async way
    public static class TaxCalculatorHelper
    {
        public static Task<double> CalculateTaxAsync(double salary)
        {             
            // I will do some heavy tax calculation here, so I want it to run asynchronously
            return Task.FromResult(500.00); // currently returning temporary value
        }
    }

    //The exisiting classes 
    public class Employee
    {
        //This method is not going to be async but What I want that Tax calculation which is heavy task that should run asynchronously        
        public double GetEmployeeFinalSalary(double salary)
        {
            var taxValue = Task.Run(async () => await TaxCalculatorHelper.CalculateTaxAsync(salary));

            //I was doing this
            //  return taxValue.Result; // I cannot use this because it blocks the calling thread until the asynchronous operation is complete

            //Is the below approach correct ?
            return taxValue.GetAwaiter().GetResult();
        }
    }

    public class SomeOtherClass
    {
        private readonly Employee _employee;
        public SomeOtherClass()
        {
            _employee = new Employee();
        }

        //This will not be async
        public void GetEmployeeCtc(double salary)
        {
            var finalCtc = _employee.GetEmployeeFinalSalary(salary);
        }
    }

任何人都可以评论并建议我最好的方法吗？
谢谢！！

Answer 1

假设这是一个 UI 应用程序，那么使用Task.Run 将同步工作推离 UI 线程是一种可接受的方法。这在 ASP.NET 应用程序中不是一个好主意。

针对您的具体情况，您需要决定如何处理GetEmployeeFinalSalary。

//This method is not going to be async but What I want that Tax calculation which is heavy task that should run asynchronously        
...
//  return taxValue.Result; // I cannot use this because it blocks the calling thread until the asynchronous operation is complete

您需要决定GetEmployeeFinalSalary 是同步的还是异步的。如果它是同步的，那么它会阻塞调用线程——这就是同步的意思。

我怀疑你确实不想要阻塞调用线程（我假设那是 UI 线程）。在这种情况下，GetEmployeeFinalSalary 必须是异步的，以便释放调用线程：

public async Task<double> GetEmployeeFinalSalaryAsync(double salary)
{
  return await Task.Run(async () => await TaxCalculatorHelper.CalculateTaxAsync(salary));
}