Question

我很难将C＃语句转换为VB。我不知道这是不是我确实使用过的lambda，但我不是那个专家，也不是分隔符，对此我了解得更少。根据Microsoft的说法，C＃'=>' symbol可以以两种不同的方式使用。

我遇到麻烦的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));
    }
}

这是我尝试过的方法，但并不是很准确；我尝试了很多变化：

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

在Visual Studio中遇到的语法错误是：

Expression does not produce a value

我去了AddOrUpdate的定义，并看到了以下重载，但是我不确定使用哪个适当的选择，也不确定一旦选择适当的重载后语法会如何。

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在寻找什么或如何正确编写它。

Answer 1

VB.NET具有two different lambda expressions：Function和Sub，后者不返回值。

在这种情况下，您要使用Sub，因为表达式不返回值。

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

如何将此C＃lambda转换为VB.net？

1 个答案: