将 Begin/End 调用函数对转换为异步函数。
              Namespace:System.Reactive.Linq
              装配: System.Reactive.dll) 中的 System.Reactive (
语法
'Declaration
Public Shared Function FromAsyncPattern(Of T1, T2) ( _
    begin As Func(Of T1, T2, AsyncCallback, Object, IAsyncResult), _
    end As Action(Of IAsyncResult) _
) As Func(Of T1, T2, IObservable(Of Unit))
'Usage
Dim begin As Func(Of T1, T2, AsyncCallback, Object, IAsyncResult)
Dim end As Action(Of IAsyncResult)
Dim returnValue As Func(Of T1, T2, IObservable(Of Unit))
returnValue = Observable.FromAsyncPattern(begin, _
    end)
public static Func<T1, T2, IObservable<Unit>> FromAsyncPattern<T1, T2>(
    Func<T1, T2, AsyncCallback, Object, IAsyncResult> begin,
    Action<IAsyncResult> end
)
public:
generic<typename T1, typename T2>
static Func<T1, T2, IObservable<Unit>^>^ FromAsyncPattern(
    Func<T1, T2, AsyncCallback^, Object^, IAsyncResult^>^ begin, 
    Action<IAsyncResult^>^ end
)
static member FromAsyncPattern : 
        begin:Func<'T1, 'T2, AsyncCallback, Object, IAsyncResult> * 
        end:Action<IAsyncResult> -> Func<'T1, 'T2, IObservable<Unit>> 
JScript does not support generic types and methods.
类型参数
- T1
第一种类型的函数。 
- T2
第二种类型的函数。 
parameters
- begin
类型: System.Func<T1、T2、 AsyncCallback、 Object、 IAsyncResult>
begin 调用函数。 
- end
类型: System.Action<IAsyncResult>
end invoke 函数。 
返回值
类型: System.Func<T1、T2、 IObservable<Unit>>
开始/结束调用函数对。