小编cet*_*346的帖子

我正在阅读本教程,了解如何在c#中异步编程并遇到错误我不知道如何解决.这是链接:http://msdn.microsoft.com/en-us/library/hh191443.aspx,错误是:

Cannot find all types required by the 'async' modifier.  
Are you targeting the wrong framework version, or missing a reference to an assembly?   

我的目标是.NET 4.0框架,并且不确定是否需要任何其他程序集.

这是代码:

public async Task<string> AccessTheWebAsync(Class1 class1, Class2 class2)
{
  // GetStringAsync returns a Task<string>. That means that when you await the 
  // task you'll get a List<string> (urlContents).
  Task<string[]> listTask = GetList(class1);

  // send message task

  // You can do work here that doesn't rely on the string from GetStringAsync. …

在获取和设置另一个具有自己独立的getter和setter的类的枚举时,我在类属性中收到构建错误.以下代码的get {}语句中存在两个相同的错误.我不确定如何解决显示的构建错误:'只有赋值,调用,递增,递减,等待和新对象表达式才能用作语句'.

   public class Data
    {

        private IEnumerable<Client> _clientData;

        private IEnumerable<Company> _companyData;

        public IEnumerable<Client> ClientData
        {
            get { _clientData ?? (_clientData = new List<Client>()); }
            set { _clientData = value; }
        }

        public IEnumerable<Company> CompanyData
        {
            get { _companyData ?? (_companyData = new List<Company>()); }
            set { _companyData = value; }
        }
    }