Sinon y'a ca :

public class PropertyModifier
{
    object toModify;

    public PropertyModifier(object toModify)
    {
        this.toModify = toModify;
    }

    public void Modify(string property, object value)
    {
        FieldInfo fi = this.toModify.GetType().GetField(property, BindingFlags.Instance | BindingFlags.NonPublic);
        if (fi != null && fi.FieldType == value.GetType())
            fi.SetValue(this.toModify, value);
    }
}