Question

我有System.Type对象（retType）。我从我传入的策略对象的反射中得到了这个。我怎样才能测试它是否可枚举？任何帮助将是最受好评的代码如下。

 Public Shared Function SerializeChanges(p As Model.Policy_2.Policy) As XmlDocument

    Dim polProps As PropertyInfo() = p.GetType().GetProperties()
        For Each pi As PropertyInfo In polProps
        Dim retType As Type = pi.PropertyType
       ' This line belowthrows an error that IEnumerable is an Interface and cannot be used as an expression
        If retType Is IEnumerable Then
           'Do Stuff

        End If
End Function

Answer 1

以下方法是检查给定类型是继承还是实现其他类型的通用方法：

Function InheritsOrImplements(child As Type, parent As Type) As Boolean
    If child Is Nothing OrElse parent Is Nothing Then
        Return False
    End If

    parent = resolveGenericTypeDefinition(parent)

    If parent.IsAssignableFrom(child) Then
        Return True
    End If

    Dim currentChild = If(child.IsGenericType, child.GetGenericTypeDefinition(), child)

    While currentChild <> GetType(Object)
        If parent = currentChild OrElse hasAnyInterfaces(parent, currentChild) Then
            Return True
        End If

        currentChild = If(currentChild.BaseType IsNot Nothing AndAlso currentChild.BaseType.IsGenericType, currentChild.BaseType.GetGenericTypeDefinition(), currentChild.BaseType)

        If currentChild Is Nothing Then
            Return False
        End If
    End While

    Return False
End Function

Function hasAnyInterfaces(parent As Type, child As Type) As Boolean
    Return child.GetInterfaces().Any(Function(childInterface) 
        Dim currentInterface = If(childInterface.IsGenericType, childInterface.GetGenericTypeDefinition(), childInterface)

        Return currentInterface = parent

    End Function)
End Function

Function resolveGenericTypeDefinition(type As Type) As Type
    Dim shouldUseGenericType = Not (type.IsGenericType AndAlso type.GetGenericTypeDefinition() <> type)
    If type.IsGenericType AndAlso shouldUseGenericType Then
        type = type.GetGenericTypeDefinition()
    End If
    Return type
End Function

取自https://github.com/shaynevanasperen/Quarks/blob/master/Quarks/TypeExtensions/InheritsOrImplements.cs

用法：

InheritsOrImplements(retType, GetType(IEnumerable))

VB.Net检查Type是否为IEnumerable

1 个答案: