Question

我试图将以下C＃代码转换为VB.NET。问题在于lambda表达式。

public class UserStore
{
    private readonly IDatabaseFactory _databaseFactory;

    private DataContext _db;
    protected DataContext Db => _db ?? (_db = _databaseFactory.GetDataContext());

    public UserStore(IDatabaseFactory databaseFactory)
    {
        _databaseFactory = databaseFactory;
    }
}

以下是我将代码转换为：

的内容

Public Class UserStore
    Private ReadOnly _databaseFactory As IDatabaseFactory

    Private _db As DataContext
    Protected Db As DataContext = Function() As DataContext
                                     If _db Is Nothing Then
                                         _db = _databaseFactory.GetDataContext()
                                     End If
                                     Return _db
                                  End Function

    Public Sub New(databaseFactory As IDatabaseFactory)
        _databaseFactory = databaseFactory
    End Sub
End Class

由于某种原因，转换后的lambda会给出错误Lambda expression cannot be converted to 'DataContext' because 'DataContext' is not a delegate type.

有谁能告诉我这里我做错了什么？

Answer 1

我正在尝试将以下C＃代码转换为VB.NET。问题在于lambda表达式。

问题在于你误认为lambda的表达式身体属性。

在C＃中

protected DataContext Db => _db ?? (_db = _databaseFactory.GetDataContext());

是一种简短的写作方式

protected DataContext Db { 
  get 
  {
    return _db ?? (_db = _databaseFactory.GetDataContext());
  }
}

根本不是lambda;如果你想将它翻译成VB，只需编写一个普通的VB属性getter。

请注意，C＃允许您使用方法执行此操作：

public Abc Foo(Bar bar) => Blah(bar);

只是一种简短的写作方式

public Abc Foo(Bar bar) 
{
  return Blah(bar);
}

将C＃Lambda转换为VB.NET

1 个答案: