LINQ的選擇C＃和VB

Question

之間不同的編譯我有正確編譯下面的C＃代碼：適用於各

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

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

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

正如你所看到的，formatted應包含list內容，與formatterCSharp。

當我試圖複製在VB這個代碼，我想出了這一點：

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 

但是我得到在VB中Select聲明兩個編譯錯誤。

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

嘗試

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

在VB.net不能指定函數名傳遞給它這樣的。

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

Answer 2

好第一關選擇查詢在VB.NET不同形成的，這裏是它應該是什麼樣子：

Dim formatted As IEnumerable(Of String) = list.Select(Function(x As String) x = formatterVisualBasic(mynumber)) 

其次，如果你想獲得相同的異常，因爲在C＃代碼，您必須添加括號函數調用formatterVisualBasic，所以它被認爲是一個功能

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