Question

根据，我有以下代码：

Public Class Fruit
    Public Property Name As String

    Public Function GetName() As String
        Return Name
    End Function
End Class

Dim list As New List(Of Fruit)

For index = 1 To 10
    Dim fruitObj As New Fruit
    fruitObj.Name = "Testing" + index.ToString()
    list.Add(fruitObj)
Next

Dim iEnumerableString As IEnumerable(Of String) = list.Select(Function(m) m.Name)

在上面的代码示例中，如果我想生成Function(m) m.Name，我应该怎么做？

所以，我可以这样称呼它：

Dim iEnumerableString As IEnumerable(Of String) =
list.Select(GenerateLambda("name"))

由于

Answer 1

您可以使用参数调用创建表达式树。

GeneratePropertyExpression方法：

Private Shared Function GeneratePropertyExpression(Of TSource, TResult)(propertyName As String) As Func(Of TSource, TResult)
    Dim parameter = Expression.Parameter(GetType(TSource), "x")
    Dim propertyExpression = Expression.[Property](parameter, propertyName)
    Return Expression.Lambda(Of Func(Of TSource, TResult))(propertyExpression, parameter).Compile()
End Function

用法：

Dim iEnumerableString As IEnumerable(Of String) = list.Select(GeneratePropertyExpression(Of Fruit, String)("Name"))

我没有测试过，所以如果它不起作用，请告诉我。

生成Lambda表达式

1 个答案: