This is the original source-code written in C#public delegate Unit UnitResolveEventHandler(object sender, ResolveEventArgs args);public event UnitResolveEventHandler UnitResolve;public static Unit GetUnitByName(string name) { Instance.unitsByName.TryGetValue(name, out result); if (Instance.UnitResolve != null) { foreach (UnitResolveEventHandler handler in Instance.UnitResolve.GetInvocationList()) { result = handler(Instance, new ResolveEventArgs(name)); } }}Using an online translator, I get this VB.NET code:Public Delegate Function UnitResolveEventHandler(sender As Object, args As ResolveEventArgs) As UnitPublic Event UnitResolve As UnitResolveEventHandlerPublic Shared Function GetUnitByName(name As String) As Unit Instance.unitsByName.TryGetValue(name, result) If Instance.UnitResolve IsNot Nothing Then For Each handler As UnitResolveEventHandler In Instance.UnitResolve.GetInvocationList() result = handler(Instance, New ResolveEventArgs(name)) Next End IfEnd FunctionThe compiler marks the event declaration with this error message:And the Instance.UnitResolve calls inside the GetUnitByName() method with this error message:How can I properly translate the code from C# to VB.NET without losing functionality? 解决方案 The customary way of returning a value from an event handler to the invocation of the event is through an argument---either a member of the event arguments class, or through a ByRef parameter on the delegate.If you have control over ResolveEventArgs and the event handler routines, you could do something like this:Public Class ResolveEventArgs '... Public ReturnValue As Unit '...End ClassIn the body of your handler (assuming the typical declaration of the event arguments as e), instead of Return (return value):e.ReturnValue = (return value) 'substitute for (return value) as appropriateThen, the body of your For Each loop would look like this:Dim args As New ResolveEventArgs(name)handler(Instance, args)result = args.ReturnValueAs an aside, the original C# code has a thread-safety issue. It could throw a NullReferenceException in the event that the last subscribed handler is removed between the null check and reading the invocation list. Whether this is serious (or a concern at all) depends on where and how it's being used. The usual way of addressing this is to store to a temporary, then do the null check and invocation list on the temporary. If you're using a recent version of the .NET languages, then you can skip the null check and use the ?. operator, which should also be safe against the particular thread-safety issue. 这篇关于将C#转换为VB，NET:具有返回类型的委托类型的事件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！
