从c#到f#的回调

我有一个f#类库:

namespace FsharpTestSystem
open System
open System.IO
open TCLoggerEntity
open TCIQuoteEntity
type TestCallback() = 
    member this.LoggerOutput() = Logger.Info("F#")
    member this.OnQuote(q : TCQuote) = Console.WriteLine(q.ToString())

将这个f#程序集的引用添加到c#项目中，我已经测试了我可以从c#中调用LoggerOutput。但是，如果我尝试在f#中执行c#事件回调，我会在下面的行中得到一个错误: 从c#:

using FsharpTestSystem;
public delegate void QuoteChangeEvent(TCQuote q);
event QuoteChangeEvent OnQuoteChange;
TestCallback fsts = new TestCallback();
api.MAPI.OnQuoteChange += fsts.OnQuote(); // this doesn't work
fsts.LoggerOutput(); // This works fine

api.MAPI.OnQuoteChange += fsts.OnQuote;