FieldInfo.SetValue Method

Definition

Namespace:

System.Reflection

Assembly:

System.Runtime.dll

Sets the value of the field for the given object to the given value.

Overloads

SetValue(Object, Object)	Sets the value of the field supported by the given object.
SetValue(Object, Object, BindingFlags, Binder, CultureInfo)	When overridden in a derived class, sets the value of the field supported by the given object.

SetValue(Object, Object)

Source:

FieldInfo.cs

Sets the value of the field supported by the given object.

public:
 void SetValue(System::Object ^ obj, System::Object ^ value);

public void SetValue (object? obj, object? value);

member this.SetValue : obj * obj -> unit

Public Sub SetValue (obj As Object, value As Object)

Parameters

obj

Object

The object whose field value will be set.

value

Object

The value to assign to the field.

Exceptions

FieldAccessException

The caller does not have permission to access this field.

Note: In .NET for Windows Store apps or the Portable Class Library, catch the base class exception, MemberAccessException, instead.

TargetException

The obj parameter is null and the field is an instance field.

Note: In .NET for Windows Store apps or the Portable Class Library, catch Exception instead.

ArgumentException

The field does not exist on the object.

-or-

The value parameter cannot be converted and stored in the field.

Examples

The following example sets the value of a field, gets and displays the value, modifies the field, and displays the result.

using namespace System;
using namespace System::Reflection;
using namespace System::Globalization;

public ref class Example
{
private:
   String^ myString;

public:
   Example()
   {
      myString = "Old value";
   }

   property String^ StringProperty 
   {
      String^ get()
      {
         return myString;
      }
   }
};

int main()
{
    Example^ myObject = gcnew Example;
    Type^ myType = Example::typeid;
    FieldInfo^ myFieldInfo = myType->GetField( "myString", 
        BindingFlags::NonPublic | BindingFlags::Instance);
      
    // Display the string before applying SetValue to the field.
    Console::WriteLine( "\nThe field value of myString is \"{0}\".", 
        myFieldInfo->GetValue( myObject ) );
    // Display the SetValue signature used to set the value of a field.
    Console::WriteLine( "Applying SetValue(Object, Object)." );

    // Change the field value using the SetValue method. 
    myFieldInfo->SetValue( myObject, "New value" );     
    // Display the string after applying SetValue to the field.
    Console::WriteLine( "The field value of mystring is \"{0}\".", 
        myFieldInfo->GetValue(myObject));
}
/* This code produces the following output:

The field value of myString is "Old value".
Applying SetValue(Object, Object).
The field value of mystring is "New value".
 */

using System;
using System.Reflection;
using System.Globalization;

public class Example
{
    private string myString;
    public Example()
    {
        myString = "Old value";
    }

    public string StringProperty
    {
        get
        {
            return myString;
        }
    }
}

public class FieldInfo_SetValue
{
    public static void Main()
    {
        Example myObject = new Example();
        Type myType = typeof(Example);
        FieldInfo myFieldInfo = myType.GetField("myString",
            BindingFlags.NonPublic | BindingFlags.Instance);

        // Display the string before applying SetValue to the field.
        Console.WriteLine( "\nThe field value of myString is \"{0}\".",
        myFieldInfo.GetValue(myObject));
        // Display the SetValue signature used to set the value of a field.
        Console.WriteLine( "Applying SetValue(Object, Object).");

        // Change the field value using the SetValue method.
        myFieldInfo.SetValue(myObject, "New value");
        // Display the string after applying SetValue to the field.
        Console.WriteLine( "The field value of mystring is \"{0}\".",
            myFieldInfo.GetValue(myObject));
    }
}

/* This code example produces the following output:

The field value of myString is "Old value".
Applying SetValue(Object, Object).
The field value of mystring is "New value".
 */

Imports System.Reflection
Imports System.Globalization

Public Class Example
   Private myString As String
   
   Public Sub New()
      myString = "Old value"
   End Sub 
   
   ReadOnly Property StringProperty() As String
      Get
         Return myString
      End Get
   End Property
End Class 


Public Module FieldInfo_SetValue
   
   Sub Main()

        Dim myObject As New Example()
        Dim myType As Type = GetType(Example)
        Dim myFieldInfo As FieldInfo = myType.GetField("myString", _
           BindingFlags.NonPublic Or BindingFlags.Instance)

        ' Display the string before applying SetValue to the field.
        Console.WriteLine(vbCrLf & "The field value of myString is ""{0}"".", _
            myFieldInfo.GetValue(myObject))
        ' Display the SetValue signature used to set the value of a field.
        Console.WriteLine("Applying SetValue(Object, Object).")

        ' Change the field value using the SetValue method. 
        myFieldInfo.SetValue(myObject, "New value")
        ' Display the string after applying SetValue to the field.
        Console.WriteLine("The field value of mystring is ""{0}"".", _
            myFieldInfo.GetValue(myObject))

    End Sub 
End Module

' This code example produces the following output:
' The field value of myString is "Old value".
' Applying SetValue(Object, Object).
' The field value of mystring is "New value".

Remarks

This method will assign value to the field reflected by this instance on object obj. If the field is static, obj will be ignored. For non-static fields, obj should be an instance of a class that inherits or declares the field. The new value is passed as an Object. For example, if the field's type is Boolean, an instance of Object with the appropriate Boolean value is passed. Before setting the value, SetValue checks to see if the user has access permission. This final method is a convenience method for calling the following SetValue method.

This method cannot be used to set values of static, init-only (readonly in C#) fields reliably. In .NET Core 3.0 and later versions, an exception is thrown if you attempt to set a value on a static, init-only field.

Note

Fully trusted code has the permissions that are needed to access and invoke private constructors, methods, fields, and properties using reflection.

Note

Starting with the .NET Framework 2.0 Service Pack 1, this method can be used to access non-public members if the caller has been granted ReflectionPermission with the ReflectionPermissionFlag.RestrictedMemberAccess flag and if the grant set of the non-public members is restricted to the caller's grant set, or a subset thereof. (See Security Considerations for Reflection.)

To use this functionality, your application should target the .NET Framework 3.5 or later.

SetValue(Object, Object, BindingFlags, Binder, CultureInfo)

Source:

FieldInfo.cs

When overridden in a derived class, sets the value of the field supported by the given object.

public:
 abstract void SetValue(System::Object ^ obj, System::Object ^ value, System::Reflection::BindingFlags invokeAttr, System::Reflection::Binder ^ binder, System::Globalization::CultureInfo ^ culture);

public abstract void SetValue (object? obj, object? value, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder? binder, System.Globalization.CultureInfo? culture);

abstract member SetValue : obj * obj * System.Reflection.BindingFlags * System.Reflection.Binder * System.Globalization.CultureInfo -> unit

Public MustOverride Sub SetValue (obj As Object, value As Object, invokeAttr As BindingFlags, binder As Binder, culture As CultureInfo)

Parameters

obj

Object

The object whose field value will be set.

value

Object

The value to assign to the field.

invokeAttr

BindingFlags

A field of Binder that specifies the type of binding that is desired (for example, Binder.CreateInstance or Binder.ExactBinding).

binder

Binder

A set of properties that enables the binding, coercion of argument types, and invocation of members through reflection. If binder is null, then Binder.DefaultBinding is used.

culture

CultureInfo

The software preferences of a particular culture.

Exceptions

FieldAccessException

The caller does not have permission to access this field.

TargetException

The obj parameter is null and the field is an instance field.

ArgumentException

The field does not exist on the object.

-or-

The value parameter cannot be converted and stored in the field.

Remarks

This method will assign value to the field reflected by this instance on obj. If the field is static, obj will be ignored. For non-static fields, obj should be an instance of a class that inherits or declares the field. The new value is passed as an Object. For example, if the field's type is Boolean, an instance of Object with the appropriate Boolean value is passed. Before setting the value, SetValue checks to see if the user has access permission.

This method cannot be used to set values of static, init-only (readonly in C#) fields reliably. In .NET Core 3.0 and later versions, an exception is thrown if you attempt to set a value on a static, init-only field.

Note

Fully trusted code has the permissions that are needed to access and invoke private constructors, methods, fields, and properties using reflection.

Note

Starting with the .NET Framework 2.0 Service Pack 1, this method can be used to access non-public members if the caller has been granted ReflectionPermission with the ReflectionPermissionFlag.RestrictedMemberAccess flag and if the grant set of the non-public members is restricted to the caller's grant set, or a subset thereof. (See Security Considerations for Reflection.)

To use this functionality, your application should target the .NET Framework 3.5 or later.