c# - C# 和 VB 之间的 Linq Select 编译方式不同

Question

我有以下可正确编译的 C# 代码:

private string formatterCSharp(int number)
{
    return "n" + number;
}

private void testInCSharp()
{
    IEnumerable<int> list = new List<int>();

    IEnumerable<string> formatted = list.Select(formatterCSharp);
}

如您所见，formatted 应该包含 list 的内容，每个内容都应用了 formatterCSharp。

当我尝试在 VB 中复制这段代码时，我想到了:

Private Function formatterVisualBasic(ByVal number As Integer) As String
    Return "n" + number
End Function

Private Sub testInVB()
    Dim list As IEnumerable(Of Integer) = New List(Of Integer)

    Dim formatted As IEnumerable(Of String) = list.Select(formatterVisualBasic)
End Sub

但是我在 VB 中的 Select 语句中遇到了两个编译错误。

BC30455
    Argument not specified for parameter 'number' of 'Private Function formatterVisualBasic(number As Integer) As String'.

BC30518
    Overload resolution failed because no accessible '[Select]' can be called with these arguments:
        Extension method 'Public Function [Select](Of TResult)(selector As Func(Of Integer, TResult)) As IEnumerable(Of TResult)' defined in 'Enumerable': Type parameter 'TResult' cannot be inferred.
        Extension method 'Public Function [Select](Of TResult)(selector As Func(Of Integer, Integer, TResult)) As IEnumerable(Of TResult)' defined in 'Enumerable': Type parameter 'TResult' cannot be inferred.

Answer 1

尝试

Dim formatted As IEnumerable(Of String) = list.Select(AddressOf formatterVisualBasic)

在 VB.net 中你不能指定函数名来传递它。

https://msdn.microsoft.com/en-us/library/y72ewk2b.aspx