生成 Lambda 表达式

Question

我大概有以下代码：

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"))

谢谢

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"))

我还没有测试过，所以如果它不起作用，请告诉我。