.NET 泛型，按名称提取对象成员值

Question

我将 2 个通用对象和一个字符串传递给一个函数，我想找到与字符串匹配的对象的属性并比较它们的值。

这是一个示例模型：

Public Structure Foo
    Public Bar As String
    Public Nan As String
    Public Tucket As String
End Structure

和调用类：

<TestMethod()> 
Public Sub TestEquality_Class_Pass_Identifier()
    _tester = new GeneralAssert
    Dim expectedFoo = New Foo With {.Bar = "asdf", .Nan = "zxcv", .Tucket = "qwer"}
    Dim actualFoo = New Foo With {.Bar = "qwer", .Nan = "zxcv", .Tucket = "qwer"}
    _tester.TestEquality(expectedFoo, actualFoo, "Bar")
End Sub

执行业务逻辑的通用断言类

Public Class GenericAssert
    Public Sub TestEquality(Of t)(expected As t, actual As t, Optional identifier As String = Nothing)
        Dim expectedType = expected.GetType(), actualType = actual.GetType()
        Assert.AreEqual(expectedType, actualType)

        If (Not identifier Is Nothing) Then
            Dim expectedProperty = expectedType.GetMember(identifier).FirstOrDefault()
            Dim actualProperty = actualType.GetMember(identifier).FirstOrDefault()

            TestEquality(*WhatHere1*, *WhatHere2*)
        End If
    End Sub
End Class

预期结果将是比较 expectedFoo ("asdf") 和 actualFoo ("qwer") 的 Bar 成员。我在 FieldInfo、PropertyInfo 或 MemberInfo 中找不到任何可以让我按名称获取分配给该属性的值的值。

Answer 1

由于结构的性质和要测试的内容都是已知的，因此我使用 FieldInfo 对象作为获取字段值的最直接方式。

Public Sub TestEquality(Of t)(expected As t, actual As t, Optional identifier As String = Nothing)
    Dim expectedType = expected.GetType()
    Dim actualType = actual.GetType()

    Assert.AreEqual(expectedType, actualType)

    If (identifier IsNot Nothing) Then
        Dim expectedField As FieldInfo = expectedType.GetField(identifier, BindingFlags.IgnoreCase Or BindingFlags.Public Or BindingFlags.Instance)
        Dim actualField As FieldInfo = actualType.GetField(identifier, BindingFlags.IgnoreCase Or BindingFlags.Public Or BindingFlags.Instance)

        Assert.AreEqual(expectedField.GetValue(expected), actualField.GetValue(actual))
    End If
End Sub

Answer 2

我不明白为什么在这种情况下不会这样做：

Public Sub AssertEquality(Of T)(ByVal expected As T, ByVal actual As T, identifier As String)

    Dim expected_prop = expected.GetType().GetProperty(identifier, BindingFlags.Instance + BindingFlags.Public)
    Dim actual_prop = actual.GetType().GetProperty(identifier, BindingFlags.Instance + BindingFlags.Public)

    Dim expected_value = expected_prop.GetValue(expected, Nothing)
    Dim actual_value = actual_prop.GetValue(actual, Nothing)

    Assert.AreEqual(expected_value, acutal_value)

End Sub

Sub Main()

    Dim expectedFoo = New Foo With {.Bar = "asdf", .Nan = "zxcv", .Tucket = "qwer"}
    Dim actualFoo = New Foo With {.Bar = "qwer", .Nan = "zxcv", .Tucket = "qwer"}

    AssertEquality(expectedFoo, actualFoo, "Bar")

End Sub