错误无法在订阅IObservable <Point>时转换lambda表达式

Question

我正在尝试使用Rx在wpf中实现标准的拖放图像.

var mouseDown = from evt in Observable.FromEventPattern<MouseButtonEventArgs>(image, "MouseLeftButtonDown")
                          select evt.EventArgs.GetPosition(image);

            var mouseUp = Observable.FromEventPattern<MouseButtonEventArgs>(this, "MouseLeftButtonUp");

            var mouseMove = from evt in Observable.FromEventPattern<MouseEventArgs>(this, "MouseMove")
                            select evt.EventArgs.GetPosition(this);

            var q = from startLocation in mouseDown
                    from endLocation in mouseMove.TakeUntil(mouseUp)
                    select new Point 
                    {
                        X = endLocation.X - startLocation.X,
                        Y = endLocation.Y - startLocation.Y
                    };

            q.ObserveOn(SynchronizationContext.Current).Subscribe(point =>
            {
                Canvas.SetLeft(image, point.X);
                Canvas.SetTop(image, point.Y);
            });

我收到错误错误 Cannot convert lambda expression to type 'System.IObserver<System.Windows.Point>' because it is not a delegate type

我错过了什么？

Answer 1

命名空间System.Reactive.Linq包含静态类Observable,它定义了常见的无功组合器的所有扩展方法.它居住在System.Reactive.dll

用于扩展方法IObservable<T>.Subscribe如Subscribe(onNext),Subscribe(onNext, onError)被然而,在定义mscorlib在静态类System.ObservableExtensions.

TL;博士:

• 对于Rx/Observable扩展方法,您需要import System.Reactive.Linq=using System.Reactive.Linq;
• 对于Subscribe重载,您需要import System=using System;

Answer 2

为了使这个更清晰的答案基于@Gideon Engelberths在问题中排在第5位,我错过了"使用系统"; 在我的班级使用指令:

using System.Reactive.Linq;
using System;

然后修复了编译器问题.谢谢基甸.