我有一個(gè)項(xiàng)目，我試圖在構(gòu)造函數(shù)中填充一些數(shù)據(jù)：public class ViewModel{
public ObservableCollection<TData> Data { get; set; }
async public ViewModel()
{
Data = await GetDataTask();
}
public Task<ObservableCollection<TData>> GetDataTask()
{
Task<ObservableCollection<TData>> task;
//Create a task which represents getting the data
return task;
}}不幸的是，我收到了一個(gè)錯(cuò)誤：改性劑async對(duì)此項(xiàng)目無(wú)效。當(dāng)然，如果我包裝一個(gè)標(biāo)準(zhǔn)方法并從構(gòu)造函數(shù)調(diào)用它：public async void Foo(){
Data = await GetDataTask();}效果很好。同樣的，如果我用舊的內(nèi)出方式GetData().ContinueWith(t => Data = t.Result);這也很管用。我只是想知道為什么我們不能打電話(huà)await直接從構(gòu)造函數(shù)中刪除。可能有很多(甚至明顯的)邊緣情況和反對(duì)它的理由，我只是想不出任何。我也四處尋找解釋?zhuān)坪跽也坏饺魏谓忉尅?
3 回答
拉丁的傳說(shuō)
TA貢獻(xiàn)1789條經(jīng)驗(yàn) 獲得超8個(gè)贊
asyncvoidTask.
TTask<T>
async void
async voidasync void
天涯盡頭無(wú)女友
TA貢獻(xiàn)1831條經(jīng)驗(yàn) 獲得超9個(gè)贊
public class ViewModel
{
public ObservableCollection<TData> Data { get; set; }
//static async method that behave like a constructor
async public static Task<ViewModel> BuildViewModelAsync()
{
ObservableCollection<TData> tmpData = await GetDataTask();
return new ViewModel(tmpData);
}
// private constructor called by the async method
private ViewModel(ObservableCollection<TData> Data)
{
this.Data=Data;
}
}
蠱毒傳說(shuō)
TA貢獻(xiàn)1895條經(jīng)驗(yàn) 獲得超3個(gè)贊
Initialize/OpenInitialize
Initialize()Initialize()
Initialize()Initialize
public MyClass{
public static async Task<MyClass> CreateAsync(...)
{
MyClass x = new MyClass();
await x.InitializeAsync(...)
return x;
}
// make sure no one but the Create function can call the constructor:
private MyClass(){}
private async Task InitializeAsync(...)
{
// do the async things you wanted to do in your async constructor
}
public async Task<int> OtherFunctionAsync(int a, int b)
{
return await OtherFunctionAsync(a, b);
}public async Task<int> SomethingAsync(){
// Create and initialize a MyClass object
MyClass myObject = await MyClass.CreateAsync(...);
// use the created object:
return await myObject.OtherFunctionAsync(4, 7);}- 3 回答
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