Articolo
11/18/2011

Type.GetField Method (String)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Searches for the public field with the specified name.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Function GetField ( _
    name As String _
) As FieldInfo

public FieldInfo GetField(
    string name
)

Parameters

name
Type: System.String
The String containing the name of the data field to get.

Return Value

Type: System.Reflection.FieldInfo
A FieldInfo object representing the public field with the specified name, if found; otherwise, nulla null reference (Nothing in Visual Basic).

Exceptions

Exception	Condition
ArgumentNullException	name is nulla null reference (Nothing in Visual Basic).
NotSupportedException	This Type object is a TypeBuilder whose CreateType method has not yet been called.

Remarks

The search for name is case-sensitive. The search includes public static and public instance fields.

If the current Type represents a constructed generic type, this method returns the FieldInfo with the type parameters replaced by the appropriate type arguments.

If the current Type represents a type parameter in the definition of a generic type or generic method, this method searches the fields of the class constraint.

Examples

The following example gets the Type object for the specified class, obtains the FieldInfo object for the field, and displays the value of the field.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.


Imports System.Reflection

Public Class MyFieldClassA
   Public Field As String = "A Field"
End Class 

Public Class MyFieldClassB
   Private myField As String = "B Field"

   Public Property Field() As String
      Get
         Return myField
      End Get
      Set(ByVal Value As String)
         If myField <> Value Then
            myField = Value
         End If
      End Set
   End Property
End Class 


Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim myFieldObjectB As New MyFieldClassB()
      Dim myFieldObjectA As New MyFieldClassA()

      Dim myTypeA As Type = GetType(MyFieldClassA)
      Dim myFieldInfo As FieldInfo = myTypeA.GetField("Field")

      Dim myTypeB As Type = GetType(MyFieldClassB)
      Dim myFieldInfo1 As FieldInfo = myTypeB.GetField("myField", _
          BindingFlags.NonPublic Or BindingFlags.Instance)

      outputBlock.Text += String.Format("The value of the public field is: '{0}'", _
          myFieldInfo.GetValue(myFieldObjectA)) + vbCrLf

      Try
         ' In Silverlight, the value of a private field cannot be accessed
         ' by using reflection.
         outputBlock.Text += String.Format("The value of the private field is: '{0}'", _
            myFieldInfo1.GetValue(myFieldObjectB)) + vbCrLf
      Catch ex As Exception
         outputBlock.Text &= ex.GetType().Name & " occurred: " & ex.Message
      End Try
   End Sub 

End Class 

' This code produces output similar to the following:
'
'The value of the public field is: 'A Field'
'FieldAccessException occurred: SilverlightApplication.MyFieldClassB.myField


using System;
using System.Reflection;

public class MyFieldClassA
{
   public string Field = "A Field";
}

public class MyFieldClassB
{
   private string field = "B Field";
   public string Field
   {
      get
      {
         return field;
      }
      set
      {
         if (field != value)
         {
            field = value;
         }
      }
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      MyFieldClassB myFieldObjectB = new MyFieldClassB();
      MyFieldClassA myFieldObjectA = new MyFieldClassA();

      Type myTypeA = typeof(MyFieldClassA);
      FieldInfo myFieldInfo = myTypeA.GetField("Field");

      Type myTypeB = typeof(MyFieldClassB);
      FieldInfo myFieldInfo1 = myTypeB.GetField("field",
          BindingFlags.NonPublic | BindingFlags.Instance);

      outputBlock.Text += String.Format("The value of the public field is: '{0}'\n",
          myFieldInfo.GetValue(myFieldObjectA));

      try
      {
         // In Silverlight, the value of a private field cannot be accessed
         // by using reflection.
         outputBlock.Text += String.Format("The value of the private field is: '{0}'\n",
            myFieldInfo1.GetValue(myFieldObjectB));
      }
      catch (Exception ex)
      {
         outputBlock.Text += ex.GetType().Name + " occurred: " + ex.Message;
      }
   }
}

/* This code produces output similar to the following:

The value of the public field is: 'A Field'
FieldAccessException occurred: MyFieldClassB.myField
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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