如何将此C＃lambda翻译成VB.net？ [关闭]

Question

我将C＃语句转换为VB时遇到了困难。我不知道这是否是一个lambda，我确实使用但是我不是那个专家，或者是一个分隔符，我更了解它。根据微软的说法，C＃'=>' symbol可以用于这两种不同的方式。

我遇到问题的C＃代码行是：

RecurringJob.AddOrUpdate(() => TextBuffer.WriteLine("text"), Cron.Minutely);

它来自sample hangfire.mvcApplication project中的Startup.cs文件。这是完整的课程：

public void Configuration(IAppBuilder app)
{
    GlobalConfiguration.Configuration.UseSqlServerStorage("DefaultConnection");
    app.UseHangfireDashboard();
    app.UseHangfireServer();
    RecurringJob.AddOrUpdate(
        () => TextBuffer.WriteLine("Recurring Job completed successfully!"), 
        Cron.Minutely);
}

the TextBuffer.WriteLine reference is:

public static void WriteLine(string value)
{
    lock (Buffer)
    {
        Buffer.AppendLine(String.Format("{0} {1}", DateTime.Now, value));
    }
}

这是我试过的，这不是很准确;我尝试了很多变化：

RecurringJob.AddOrUpdate(Function() TextBuffer.WriteLine("text"), Cron.Minutely)

我在Visual Studio中得到的语法错误是：

Expression does not produce a value

我去了AddOrUpdate的定义，并看到了以下重载，但我不确定哪个是正确的选择使用，也不确定一旦我选择正确的重载语法将如何看起来。

Public Shared Sub AddOrUpdate(methodCall As Expression(Of Action), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(methodCall As Expression(Of Action), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(methodCall As Expression(Of Func(Of Task)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(methodCall As Expression(Of Func(Of Task)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(recurringJobId As String, methodCall As Expression(Of Action), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(recurringJobId As String, methodCall As Expression(Of Action), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(recurringJobId As String, methodCall As Expression(Of Func(Of Task)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(recurringJobId As String, methodCall As Expression(Of Func(Of Task)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(methodCall As Expression(Of Action(Of T)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(methodCall As Expression(Of Action(Of T)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(methodCall As Expression(Of Func(Of T, Task)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(methodCall As Expression(Of Func(Of T, Task)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(recurringJobId As String, methodCall As Expression(Of Action(Of T)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(recurringJobId As String, methodCall As Expression(Of Action(Of T)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(recurringJobId As String, methodCall As Expression(Of Func(Of T, Task)), cronExpression As Func(Of String), Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")
Public Shared Sub AddOrUpdate(Of T)(recurringJobId As String, methodCall As Expression(Of Func(Of T, Task)), cronExpression As String, Optional timeZone As TimeZoneInfo = Nothing, Optional queue As String = "default")

我只是不明白该方法正在寻找什么或如何正确地编写它。

Answer 1

VB.NET有two different lambda expressions：Function，它返回一个值，Sub，它没有。

在这种情况下，您希望使用Sub，因为您的表达式不返回值。

RecurringJob.AddOrUpdate(Sub() TextBuffer.WriteLine("text"), Cron.Minutely)