取得物件的屬性名稱、型別（含Nullable）、值

2012-03-07

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Dotblogs 的標籤：隨手記 ,VB.Net

做個筆記。筆記重點是若該屬性是實值型別，又允許 Nullable，則有值和 Null 時，要如何呈現：

Imports System.Reflection

Module Module1

    Sub Main()
        Dim u As User = New User()
        u.Birthday = Now
        GetEntityProperty(u)

        Console.ReadLine()
    End Sub

    ''' <summary>
    ''' Gets the entity property.
    ''' </summary>
    ''' <typeparam name="T"></typeparam>
    ''' <param name="Entity">The entity.</param>
    ''' <info>Author: Leo; Date: 2012/3/7 </info>
    Public Sub GetEntityProperty(Of T)(ByVal Entity As T)
        Dim ObjType As Type = Entity.GetType()
        For Each p As PropertyInfo In ObjType.GetProperties()
            Dim val = p.GetValue(Entity, Nothing)
            Dim valType = If(IsNothing(val), p.PropertyType.Name, val.GetType.Name)
            Console.WriteLine(String.Format("Name = {0}, Type = {1}, value = {2}", _
                                            p.Name, valType, If(IsNothing(val), "Null", val.ToString())))
        Next
    End Sub
End Module

User Class 就不貼出來了，反正就是一個對應 Model 的 Class。

輸出結果：

Name = DataKeys, Type = List`1, value = Null
Name = Name, Type = String, value = Null
Name = Birthday, Type = DateTime, value = 2012/3/7 下午 03:12:36
Name = Age, Type = Int32, value = 0
Name = Pay, Type = Nullable`1, value = Null
Name = Address, Type = String, value = Null
Name = Interests, Type = List`1, value = Null

---------

剛同事說，可不可以就算是 Nullable 的欄位，沒給值一樣能顯示屬性真正的型別。當然可以，調整如下：

    Public Sub GetEntityProperty(Of T)(ByVal Entity As T)
        Dim ObjType As Type = Entity.GetType()
        For Each p As PropertyInfo In ObjType.GetProperties()
            Dim val = p.GetValue(Entity, Nothing)
            'Dim valType As String = If(IsNothing(val), p.PropertyType.Name, val.GetType.Name)
            Dim underlyingType As Type = Nullable.GetUnderlyingType(p.PropertyType)
            Dim valType As String = If(IsNothing(underlyingType), p.PropertyType.Name, underlyingType.Name)
            Console.WriteLine(String.Format("Name = {0}, Type = {1}, value = {2}", _
                                            p.Name, valType, If(IsNothing(val), "Null", val.ToString())))
        Next
    End Sub

指後我在 User Class 裡再多加一個 OnjobDate 的日期欄位，一樣允許 Nullable，不設值，好和 Birthday 區隔。以下為輸出結果：

Name = DataKeys, Type = List`1, value = Null
Name = Name, Type = String, value = Null
Name = Birthday, Type = DateTime, value = 2012/3/7 下午 03:43:31
Name = OnjobDate, Type = DateTime, value = Null
Name = Age, Type = Int32, value = 0
Name = Pay, Type = Decimal, value = Null
Name = Address, Type = String, value = Null
Name = Interests, Type = List`1, value = Null

--------
沒什麼特別的~
不過是一些筆記而已

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