VB.NET 和 Visual Studio 2010 是否支持多行匿名方法？

发布于 2024-09-26 00:59:06 字数 588 浏览 0 评论 0原文

我发现这个答案在VS2010实际发布之前就被问到并得到了回答。

他们说

VB9只有单行匿名功能。我们正在添加完整的声明以及 VB10 中的多行 lambda。

但我尝试将此代码添加

 Dim test2 = Function(t1 As T, t2 As T) (
 Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
 Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
 Return val1.CompareTo(val2)
 )

到 Visual Studio 2010 中的 .NET Framework 4.0 项目中，但它无法编译。

你现在知道这个功能是否真的实现了以及我做错了什么吗？

原文

I found that this answer was asked and answered before VS2010 was actually released.

They say that

VB9 has only single-line anonymous
functions. We're adding full statement
and multi-line lambdas in VB10.

But I tried to add this code

 Dim test2 = Function(t1 As T, t2 As T) (
 Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
 Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
 Return val1.CompareTo(val2)
 )

to a .NET Framework 4.0 project in Visual Studio 2010 and it does not compile.

Do you now if this feature is really implemented and what I am doing wrong?

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讽刺将军 2024-10-03 00:59:06

我相信您只是错过了“结束功能”行。试试这个：

 Dim test2 = (Function(t1 As T, t2 As T)
 Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
 Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
 Return val1.CompareTo(val2)
 End Function)

I believe you are only missing your 'End Function' line. Try this:

 Dim test2 = (Function(t1 As T, t2 As T)
 Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
 Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
 Return val1.CompareTo(val2)
 End Function)

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那片花海 2024-10-03 00:59:06

您缺少 End Function 并且您试图将函数体括在括号中，这是错误的。这应该有效：

Dim test2 = Function(t1 As T, t2 As T)
    Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
    Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
    Return val1.CompareTo(val2)
End Function

此功能记录在此处：

Lambda 表达式 (Visual Basic)

You are missing End Function and you are trying to enclose the function body in parenthesis, which is wrong. This should work:

Dim test2 = Function(t1 As T, t2 As T)
    Dim val1 As IComparable = DirectCast(prop.GetValue(t1), IComparable)
    Dim val2 As IComparable = DirectCast(prop.GetValue(t2), IComparable)
    Return val1.CompareTo(val2)
End Function

This feature is documented here:

Lambda Expressions (Visual Basic)

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沙沙粒小 2024-10-03 00:59:06

以下是您可能会觉得有用的东西。请注意如何立即调用声明的方法。

Dim food = New With {
    .ID = 1,
    .Name = "Carrot",
    .Type = (
        Function(name As String)
            If String.IsNullOrEmpty(name) Then Return String.Empty

            Select Case name.ToLower()
                Case "apple", "tomato": Return "Fruit"
                Case "potato": Return "Vegetable"
            End Select

            Return "Meat"
        End Function
    )(.Name)
}
Dim type = food.Type

Here is something you might find useful. Note how the method declared is instantly invoked.

Dim food = New With {
    .ID = 1,
    .Name = "Carrot",
    .Type = (
        Function(name As String)
            If String.IsNullOrEmpty(name) Then Return String.Empty

            Select Case name.ToLower()
                Case "apple", "tomato": Return "Fruit"
                Case "potato": Return "Vegetable"
            End Select

            Return "Meat"
        End Function
    )(.Name)
}
Dim type = food.Type

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