FieldInfo.IsInitOnly Property

.NET Framework Class Library

Gets a value indicating whether the field can only be set in the body of the constructor.

[Visual Basic]
Public ReadOnly Property Is As Boolean
[C#]
public bool IsInitOnly {get;}
[C++]
public: __property bool get_IsInitOnly();
[JScript]
public function get IsInitOnly() : Boolean;

Property Value

true if the field has the InitOnly attribute set; otherwise, false.

Remarks

If the returned value is true, the field can only be initialized, and is read-only thereafter.

To get the IsInitOnly property, first get the class Type. From the Type, get the FieldInfo. From the FieldInfo, get the IsInitOnly property. To access a non-public field, set the BindingFlags to NonPublic and choose either Static or Instance BindingFlags in the GetField method.

The IsInitOnly property is set when the FieldAttributes.InitOnly attribute is set.

Example

In the following example, two fields are created. The second field is read-only, having no set accessor, and IsInitOnly is set to true.

[Visual Basic] 
Imports System
Imports System.Reflection
Imports Microsoft.VisualBasic


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

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

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

[C#] 

using System;
using System.Reflection;

 //Make two fields, one public and one read-only.
public class Myfielda
{
    public string field = "A - public field";
    public string Field
    {
        get{return field;}
        set{if(field!=value){field=value;}}
    }
}
public class Myfieldb
{
    readonly string field = "B - readonly field";
    public string Field
    {
        get{return 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 = Type.GetType("Myfielda");
        FieldInfo Myfieldinfoa = MyTypea.GetField("field",
            BindingFlags.Public|BindingFlags.Instance);
        Type MyTypeb = Type.GetType("Myfieldb");
        FieldInfo Myfieldinfob = MyTypeb.GetField("field",
            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;
    }
}

[C++] 
#using <mscorlib.dll>
using namespace System;
using namespace System::Reflection;

//Make two fields, one public and one read-only.
public __gc class Myfielda
{
public:
    String* field;
    Myfielda() : field(S"A - public field") {}
    __property String* get_Field() {
        return field;
    }
    __property void set_Field(String* value) {
        if(field!=value){
            field=value;
        }
    }
};
public __gc class Myfieldb
{
    String* const field;
public:
    Myfieldb() : field(S"B - readonly field") {}
    __property String* get_Field() {
        return field;
    }
};

int main()
{
    Console::WriteLine(S"\nReflection.FieldInfo");
    Myfielda* myfielda = new Myfielda();
    Myfieldb* myfieldb = new Myfieldb();

    //Get the Type and FieldInfo.
    Type* MyTypea = Type::GetType(S"Myfielda");
    FieldInfo* Myfieldinfoa = MyTypea->GetField(S"field",
        static_cast<BindingFlags>(BindingFlags::Public|BindingFlags::Instance));
    Type* MyTypeb = Type::GetType(S"Myfieldb");
    FieldInfo* Myfieldinfob = MyTypeb->GetField(S"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 = S"A- modified";
    //Myfieldb.field = "B- modified";

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

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

    return 0;
}

[JScript] 
//Make two fields, one public and one read-only.
public class Myfielda
{
   public var field : String = "A public field";
   public function get Field() : String {
       return field;
   }
   public function set Field( value : String ) {
       if (field!=value) field=value;
   }
}

public class Myfieldb
{
   const field : String = "B readonly field";
   public function get Field() : String {
       return field;
   }
}

public class Myfieldinfo
{
   public static function Main() : void
   {
      Console.WriteLine("\nReflection.FieldInfo");
      var myfielda : Myfielda = new Myfielda();
      var myfieldb : Myfieldb = new Myfieldb();
 
      //Get the Type and FieldInfo.
      var MyTypea : Type = Type.GetType("Myfielda");
      var Myfieldinfoa : FieldInfo = MyTypea.GetField("field", BindingFlags.Instance|BindingFlags.Public);
      var MyTypeb : Type = Type.GetType("Myfieldb");
      var Myfieldinfob : FieldInfo = MyTypeb.GetField("field", BindingFlags.Instance|BindingFlags.Public);
 
      //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.
      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.
      Console.Write("\n{0} - {1}, IsLiteral = {2} ",
         MyTypeb.FullName,
         Myfieldinfob.GetValue(myfieldb),
         Myfieldinfob.IsLiteral);
   }
}
Myfieldinfo.Main();

This code produces the following output:

Reflection.FieldInfo

Myfielda - A- modified, IsInitOnly = False

Myfieldb - B readonly field, IsInitOnly = True

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

Property Value

Remarks

Example

Requirements

See Also