FieldInfo.IsInitOnly 屬性

定義

命名空間:

System.Reflection

組件:

System.Runtime.dll

來源:

FieldInfo.cs

取得值，指出欄位是否只能在建構函式主體中設定。

public:
 property bool IsInitOnly { bool get(); };

public bool IsInitOnly { get; }

member this.IsInitOnly : bool

Public ReadOnly Property IsInitOnly As Boolean

屬性值

Boolean

如果欄位已設定 true 屬性，則為 InitOnly，否則為 false。

範例

在下列範例中，會建立兩個欄位。 第二個欄位是唯讀的，沒有 set 存取子，而且 IsInitOnly 設定為 true 。

using namespace System;
using namespace System::Reflection;

//Make two fields, one public and one read-only.
public ref class Myfielda
{
public:
   String^ field;
   Myfielda()
      : field( "A - public field" )
   {}


   property String^ Field 
   {
      String^ get()
      {
         return field;
      }

      void set( String^ value )
      {
         if ( field != value )
         {
            field = value;
         }
      }

   }

};

public ref class Myfieldb
{
private:
   String^ const field;

public:
   Myfieldb()
      : field( "B - readonly field" )
   {}


   property String^ Field 
   {
      String^ get()
      {
         return field;
      }

   }

};

int main()
{
   Console::WriteLine( "\nReflection.FieldInfo" );
   Myfielda^ myfielda = gcnew Myfielda;
   Myfieldb^ myfieldb = gcnew Myfieldb;
   
   //Get the Type and FieldInfo.
   Type^ MyTypea = Type::GetType( "Myfielda" );
   FieldInfo^ Myfieldinfoa = MyTypea->GetField( "field", static_cast<BindingFlags>(BindingFlags::Public | BindingFlags::Instance) );
   Type^ MyTypeb = Type::GetType( "Myfieldb" );
   FieldInfo^ Myfieldinfob = MyTypeb->GetField( "field", static_cast<BindingFlags>(BindingFlags::NonPublic | BindingFlags::Instance) );
   
   //Modify the fields.
   //Note that Myfieldb is not modified, as it is
   //read-only (IsInitOnly is True).
   myfielda->field = "A- modified";
   
   //Myfieldb.field = "B- modified";
   //For the first field, get and display the name, field, and IsInitOnly state.
   Console::Write( "\n{0} - {1}, IsInitOnly = {2} ", MyTypea->FullName, Myfieldinfoa->GetValue( myfielda ), Myfieldinfoa->IsInitOnly );
   
   //For the second field get and display the name, field, and IsInitOnly state.
   Console::Write( "\n{0} - {1}, IsInitOnly = {2} ", MyTypeb->FullName, Myfieldinfob->GetValue( myfieldb ), Myfieldinfob->IsInitOnly );
   return 0;
}

using System;
using System.Reflection;

//Make two fields, one public and one read-only.
public class Myfielda
{
    public string field = "A - public modifiable field";
}
public class Myfieldb
{
    public readonly string field = "B - readonly field";
}

public class Myfieldinfo
{
    public static int Main()
    {
        Console.WriteLine("\nReflection.FieldInfo");
        Myfielda Myfielda = new Myfielda();
        Myfieldb Myfieldb = new Myfieldb();

        //Get the Type and FieldInfo.
        Type MyTypea = typeof(Myfielda);
        FieldInfo Myfieldinfoa = MyTypea.GetField("field",
            BindingFlags.Public | BindingFlags.Instance);
        Type MyTypeb = typeof(Myfieldb);
        FieldInfo Myfieldinfob = MyTypeb.GetField("field",
            BindingFlags.Public | BindingFlags.Instance);

        //Modify the fields.
        //Note that Myfieldb is not modified, as it is
        //read-only (IsInitOnly is True).
        Myfielda.field = "A - modified";
        //Myfieldb.field = "B - modified";

        //For the first field, get and display the name, field, and IsInitOnly state.
        Console.Write("\n{0} - {1}, IsInitOnly = {2} ",
            MyTypea.FullName,
            Myfieldinfoa.GetValue(Myfielda),
            Myfieldinfoa.IsInitOnly);

        //For the second field get and display the name, field, and IsInitOnly state.
        Console.Write("\n{0} - {1}, IsInitOnly = {2} ",
            MyTypeb.FullName,
            Myfieldinfob.GetValue(Myfieldb),
            Myfieldinfob.IsInitOnly);

        return 0;
    }
}

Imports System.Reflection

'Make two fields, one public and one read-only.
Public Class Myfielda
    Public field As String = "A - public modifiable field"
End Class

Public Class Myfieldb
    Public ReadOnly field As String = "B - readonly field"
End Class

Public Class Myfieldinfo
    Public Shared Function Main() As Integer
        Console.WriteLine("Reflection.FieldInfo")
        Console.WriteLine()
        Dim Myfielda As New Myfielda()
        Dim Myfieldb As New Myfieldb()

        'Get the Type and FieldInfo.
        Dim MyTypea As Type = GetType(Myfielda)
        Dim Myfieldinfoa As FieldInfo = MyTypea.GetField("field", _
            BindingFlags.Public Or BindingFlags.Instance)
        Dim MyTypeb As Type = GetType(Myfieldb)
        Dim Myfieldinfob As FieldInfo = MyTypeb.GetField("field", _
            BindingFlags.Public Or BindingFlags.Instance)

        'Modify the fields.
        'Note that Myfieldb is not modified, as it is
        'read-only (IsInitOnly is True).
        Myfielda.field = "A - modified"
        'For the first field, get and display the name, field, and IsInitOnly state.
        Console.WriteLine("{0} - {1}, IsInitOnly = {2} ", MyTypea.FullName, _
            Myfieldinfoa.GetValue(Myfielda), Myfieldinfoa.IsInitOnly)
        'For the second field get and display the name, field, and IsInitOnly state.
        Console.WriteLine("{0} - {1}, IsInitOnly = {2} ", MyTypeb.FullName, _
            Myfieldinfob.GetValue(Myfieldb), Myfieldinfob.IsInitOnly)

        Return 0
    End Function 'Main
End Class

此程式碼會產生下列輸出：

Reflection.FieldInfo

Myfielda - A- modified, IsInitOnly = False

Myfieldb - B readonly field, IsInitOnly = True

備註

如果傳回的值是 true ，則欄位只能初始化，且之後為唯讀。

若要取得 IsInitOnly 屬性，請先取得 類別 Type 。 從 取得 TypeFieldInfo 。 FieldInfo從 取得 IsInitOnly 屬性。 若要存取非公用欄位， BindingFlags.NonPublic 請在 方法中 GetField 結合 或 兩者 BindingFlags.StaticBindingFlags.Instance 。

屬性 IsInitOnly 設定時 FieldAttributes.InitOnly 會設定屬性。

另請參閱

• FieldAttributes
• GetField(String, BindingFlags)
• Type