PropertyInfo.GetValue 方法

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

public:
 System::Object ^ GetValue(System::Object ^ obj);

public object GetValue (object obj);

public object? GetValue (object? obj);

member this.GetValue : obj -> obj

Public Function GetValue (obj As Object) As Object

參數

傳回

指定物件的屬性值。

範例

下列範例會定義具有兩個屬性的 Planet 類別：Name，行星的名稱;和 Distance，行星與地球的距離。 此範例會具現化代表木星行星的 Planet 物件，並將它傳遞給 GetPropertyValues 方法，以顯示屬性的相關信息，並使用 GetValue 方法來取得每個 Planet 屬性的值。

using System;
using System.Reflection;

public class Planet
{
   private String planetName;
   private Double distanceFromEarth;
   
   public Planet(String name, Double distance)
   {
      planetName = name;
      distanceFromEarth = distance;
   } 

   public String Name
   { get { return planetName; } }
   
   public Double Distance 
   { get { return distanceFromEarth; }
     set { distanceFromEarth = value; } }
}

public class Example
{
   public static void Main()
   {
      Planet jupiter = new Planet("Jupiter", 3.65e08);
      GetPropertyValues(jupiter);
   }
   
   private static void GetPropertyValues(Object obj)
   {
      Type t = obj.GetType();
      Console.WriteLine("Type is: {0}", t.Name);
      PropertyInfo[] props = t.GetProperties();
      Console.WriteLine("Properties (N = {0}):", 
                        props.Length);
      foreach (var prop in props)
         if (prop.GetIndexParameters().Length == 0)
            Console.WriteLine("   {0} ({1}): {2}", prop.Name,
                              prop.PropertyType.Name,
                              prop.GetValue(obj));
         else
            Console.WriteLine("   {0} ({1}): <Indexed>", prop.Name,
                              prop.PropertyType.Name);
   }
}
// The example displays the following output:
//       Type is: Planet
//       Properties (N = 2):
//          Name (String): Jupiter
//          Distance (Double): 365000000

Imports System.Reflection

Public Class Planet
   Private planetName As String
   Private distanceFromEarth As Double
   
   Public Sub New(name As String, distance As Double)
      planetName = name
      distanceFromEarth = distance
   End Sub 

   Public ReadOnly Property Name As String
      Get
         Return planetName
      End Get
   End Property
   
   Public Property Distance As Double
      Get
         Return distanceFromEarth
      End Get
      Set
         distanceFromEarth = value
      End Set
   End Property
End Class

Module Example
   Public Sub Main()
      Dim jupiter As New Planet("Jupiter", 3.65e08)
      GetPropertyValues(jupiter)
   End Sub
   
   Private Sub GetPropertyValues(obj As Object)
      Dim t As Type = obj.GetType()
      Console.WriteLine("Type is: {0}", t.Name)
      Dim props() As PropertyInfo = t.GetProperties()
      Console.WriteLine("Properties (N = {0}):", 
                        props.Length)
      For Each prop In props
         If prop.GetIndexParameters().Length = 0 Then
            Console.WriteLine("   {0} ({1}): {2}", prop.Name,
                              prop.PropertyType.Name,
                              prop.GetValue(obj))
         Else
            Console.WriteLine("   {0} ({1}): <Indexed>", prop.Name,
                              prop.PropertyType.Name)
         End If                  
      Next                         
   End Sub
End Module
' The example displays the following output:
'       Type is: Planet
'       Properties (N = 2):
'          Name (String): Jupiter
'          Distance (Double): 365000000

備註

您可以呼叫 GetValue(Object) 多載來擷取非索引屬性的值;如果您嘗試擷取索引屬性的值，方法會擲回 TargetParameterCountException 例外狀況。 您可以呼叫 GetIndexParameters 方法來判斷屬性是否已編製索引。 如果傳回 ParameterInfo 陣列的長度為零，則不會編製屬性的索引。

這是一個便利的方法，提供抽象 GetValue(Object, BindingFlags, Binder, Object[], CultureInfo) 方法的實作，並將 BindingFlags 參數設定為 BindingFlags.Default、Binder 設定為 null、索引值的物件陣列設定為 null，以及設定為 null的 CultureInfo。

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

public:
 virtual System::Object ^ GetValue(System::Object ^ obj, cli::array <System::Object ^> ^ index);

public virtual object GetValue (object obj, object[] index);

public virtual object? GetValue (object? obj, object?[]? index);

abstract member GetValue : obj * obj[] -> obj
override this.GetValue : obj * obj[] -> obj

Public Overridable Function GetValue (obj As Object, index As Object()) As Object

參數

傳回

指定物件的屬性值。

實作

例外狀況

範例

下列範例示範如何取得索引屬性的值。 String.Chars[] 屬性是 String 類別的預設屬性（C# 中的索引器）。

using System;
using System.Reflection;

class Example
{
    public static void Main()
    {
        string test = "abcdefghijklmnopqrstuvwxyz";

        // Get a PropertyInfo object representing the Chars property.
        PropertyInfo pinfo = typeof(string).GetProperty("Chars");

        // Show the first, seventh, and last letters
        ShowIndividualCharacters(pinfo, test, 0, 6, test.Length - 1);

        // Show the complete string.
        Console.Write("The entire string: ");
        for (int x = 0; x < test.Length; x++)
        {
            Console.Write(pinfo.GetValue(test, new Object[] {x}));
        }
        Console.WriteLine();
    }

    static void ShowIndividualCharacters(PropertyInfo pinfo, 
                                         object value,
                                         params int[] indexes)
    {
       foreach (var index in indexes) 
          Console.WriteLine("Character in position {0,2}: '{1}'",
                            index, pinfo.GetValue(value, new object[] { index }));
       Console.WriteLine();                          
    }                                      
}
// The example displays the following output:
//    Character in position  0: 'a'
//    Character in position  6: 'g'
//    Character in position 25: 'z'
//    
//    The entire string: abcdefghijklmnopqrstuvwxyz

Imports System.Reflection

Module Example
    Sub Main()
        Dim test As String = "abcdefghijklmnopqrstuvwxyz"

        ' Get a PropertyInfo object representing the Chars property.
        Dim pinfo As PropertyInfo = GetType(String).GetProperty("Chars")

        ' Show the first, seventh, and last characters.
        ShowIndividualCharacters(pinfo, test, { 0, 6, test.Length - 1 })

        ' Show the complete string.
        Console.Write("The entire string: ")
        For x As Integer = 0 To test.Length - 1
            Console.Write(pinfo.GetValue(test, { x }))
        Next
        Console.WriteLine()
    End Sub

    Sub ShowIndividualCharacters(pinfo As PropertyInfo, 
                                 value As Object, 
                                 ParamArray indexes() As Integer)
       For Each index In indexes 
          Console.WriteLine("Character in position {0,2}: '{1}'",
                            index, pinfo.GetValue(value, { index }))
       Next
       Console.WriteLine()                          
    End Sub   
End Module
' The example displays the following output:
'       Character in position  0: 'a'
'       Character in position  6: 'g'
'       Character in position 25: 'z'
'       
'       The entire string: abcdefghijklmnopqrstuvwxyz

備註

若要判斷屬性是否已編製索引，請使用 GetIndexParameters 方法。 如果產生的陣列有0（零） 個元素，則不會編製屬性的索引。

這是一個便利的方法，提供抽象 GetValue 方法的實作，其中具有 Default的 BindingFlags 參數、設定為 null的 Binder，以及設定為 null的 CultureInfo。

因為靜態屬性屬於類型，而不是個別物件，因此傳遞 null 做為物件自變數來取得靜態屬性。 例如，使用下列程式代碼取得 CultureInfo 的靜態 CurrentCulture 屬性：

PropertyInfo CurCultProp =
    (typeof(CultureInfo)).GetProperty("CurrentCulture");
Console.WriteLine("CurrCult: " +
    CurCultProp.GetValue(null,null));

若要使用 GetValue 方法，請先取得 類別 Type。 從 Type取得 PropertyInfo。 從 PropertyInfo使用 GetValue 方法。

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

來源:

PropertyInfo.cs

public:
 abstract System::Object ^ GetValue(System::Object ^ obj, System::Reflection::BindingFlags invokeAttr, System::Reflection::Binder ^ binder, cli::array <System::Object ^> ^ index, System::Globalization::CultureInfo ^ culture);

public abstract object? GetValue (object? obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder? binder, object?[]? index, System.Globalization.CultureInfo? culture);

public abstract object GetValue (object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, object[] index, System.Globalization.CultureInfo culture);

abstract member GetValue : obj * System.Reflection.BindingFlags * System.Reflection.Binder * obj[] * System.Globalization.CultureInfo -> obj

Public MustOverride Function GetValue (obj As Object, invokeAttr As BindingFlags, binder As Binder, index As Object(), culture As CultureInfo) As Object

參數

傳回

指定物件的屬性值。

實作

例外狀況

備註

若要判斷屬性是否已編製索引，請使用 GetIndexParameters 方法。 如果產生的陣列有0（零） 個元素，則不會編製屬性的索引。

因為靜態屬性屬於類型，而不是個別物件，因此傳遞 null 做為物件自變數來取得靜態屬性。 例如，使用下列程式代碼取得 CultureInfo 的靜態 CurrentCulture 屬性：

PropertyInfo CurCultProp =
       (typeof(CultureInfo)).GetProperty("CurrentCulture");
Console.WriteLine("CurrCult: " +
       CurCultProp.GetValue(null,null));

若要使用 GetValue 方法，請先取得 類別 Type。 從 Type取得 PropertyInfo。 從 PropertyInfo使用 GetValue 方法。

另請參閱

• Binder
• BindingFlags
• CultureInfo