在 VB.NET 中正确使用 async/await？
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Correct use of async/await in VB.NET?
提问by Cuthbert
The following code won't compile with the error: Value of type 'System.Threading.Tasks.Task(Of System.Data.DataTable)' cannot be converted to 'System.Data.DataTable
以下代码不会编译并出现错误： Value of type 'System.Threading.Tasks.Task(Of System.Data.DataTable)' cannot be converted to 'System.Data.DataTable
Private m_country_dt As DataTable = getCountriesAsync()
Private Async Function getCountriesAsync() As Task(Of DataTable)
Dim dt As DataTable = Await Task(Of DataTable).Factory.StartNew(Function() getCountries_dt())
Return dt
End Function
Private Function getCountries_dt() As DataTable
Dim sp As New dbCore.StoredProcedure
Return sp.GetAllCountries()
End Function
Can someone tell me what I might be doing wrong here? GetAllCountriesis a function that queries a SQL database for.. all the countries in it and returns this in a DataTable. This code is located inside of a Module.
有人可以告诉我我在这里可能做错了什么吗？GetAllCountries是一个查询 SQL 数据库中所有国家/地区的函数，并以DataTable. 此代码位于模块内部。
回答by Stephen Cleary
You have to Awaitit to unwrap the Task (Of DataTable).
你必须用Await它来解开Task (Of DataTable).
On a side note, you should prefer Task.Runover Task.Factory.StartNew(I describe why on my blog). Though in this case, I would try to use the ADO.NET async methods instead of just running the synchronous methods on a background task.
在一个侧面说明，你应该更喜欢Task.Run了Task.Factory.StartNew（我说明为什么在我的博客）。尽管在这种情况下，我会尝试使用 ADO.NET 异步方法，而不是仅在后台任务上运行同步方法。
