Question

我有以下正确编译的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应包含list的内容，并formatterCSharp应用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。

当我尝试在VB中复制此代码时，我想出了这个：

Select

但是我在VB中的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.语句中遇到两个编译错误。

assert false : 'If you see me, colons are allowed!

Answer 1

尝试

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

在VB.net中，您无法指定函数名称来传递它。

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

Answer 2

好的首先，选择查询在VB.NET中的形式不同，这里应该看起来如何：

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

其次，如果您想获得与C＃代码相同的异常，则必须在函数调用 formatterVisualBasic 中添加括号，以便将其识别为函数

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

Linq选择在C＃和VB之间进行不同的编译

2 个答案: