Question

Is there a way in C# to create a field which is a reference to another field which is a value type?

class myClass
{
    bool b1;

    public void method1(ref bool b)
    {
        b1 = b;
    }
}

I want b1 to reference the value of b, just as b references the value of the original argument, so that changes to b1 will affect the original argument.

EDIT:

What I’m trying to achieve is a myCheckBox class which automatically updates a field. See: How do I change a value argument from within an event handler?

Answer 1

Well… there is a very contort way 🙂 of course.
That is, using reflection!
You cannot get the address of a field, but we can use reflection.

Reflection is slower than accessing directly a field, i warn you.
And really, accessing private fields of other classes is a really bad practice!
Is however useful sometime for some dirty hacks when you don’t have control of code written by other people.

Here the example, but i keep saying, it is not a good practice, is here only for curiosity and for educational purposes!

Fine another way to access your field, using properties or using a class that modify your properties.

// Our FieldReference class that internally uses reflection to get or set a field value.
public class FieldReference<T>
{
    private object ownerObject;
    private FieldInfo fieldInfo;

    public FieldReference(object ownerObject, string fieldName)
    {
        this.ownerObject = ownerObject;
        this.fieldInfo = ownerObject.GetType().GetField(fieldName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
    }

    public FieldReference(object ownerObject, FieldInfo fieldInfo)
    {
        this.ownerObject = ownerObject;
        this.fieldInfo = fieldInfo;
    }

    public T Value
    {
        get { return (T)this.fieldInfo.GetValue(this.ownerObject); }
        set { this.fieldInfo.SetValue(this.ownerObject, value); }
    }
}

// Our dummy class
public class MyClass
{
    // Our field we want to expose.
    private int myField;

    public MyClass(int value)
    {
        this.myField = value;
    }

    // Just a function we use to print the content of myField.
    public override string ToString()
    {
        return this.myField.ToString();
    }
}

class Program
{
    public static void Main()
    {
        // We create our class.
        MyClass mc = new MyClass(5);

        // We print field value, should be 5 :)
        Console.WriteLine(mc.ToString());

        // We create our field reference
        FieldReference<int> fieldref = new FieldReference<int>(mc, "myField");

        // We set the value using field reference.
        // Note, we accessed a private field :)
        fieldref.Value = 100;

        // Now we print the value, should be 100!
        Console.WriteLine(mc.ToString());

        Console.ReadLine();
    }
}