How do I translate this C# lambda into VB.net?

Question

I'm having difficulty translating a C# statement into VB. I don't know if this is a lambda, which I do use but I'm not that expert with, or a separator, which I understand even less. According to Microsoft, the C# '=>' symbol can be used in those 2 different ways.

The line of C# code I'm having trouble with is:

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

It is from the Startup.cs file in the sample hangfire.mvcApplication project. This is the full Class:

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));
    }
}

This is what I tried, which is not really accurate; I tried a lot of variations:

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

And the syntax error I get in Visual Studio is:

Expression does not produce a value

I went to the definitions for AddOrUpdate and saw the following overloads, but I'm not sure which is the proper selection to use nor how the syntax would look once I pick the proper overload.

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")

I just don't understand what the method is looking for or how to properly write it.

Answer 1

VB.NET has two different lambda expressions: Function, which returns a value, and Sub, which does not.

In this case, you want to use Sub, as your expression does not return a value.

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