从 FieldInfo 获取对象实例

Question

So my problem is this: I have an object instance represented only by FieldInfo. I have no other access to that object. Is it possible to get that object instance only through the field info like so?

MyObject myObject = fieldInfo.SomeMethodOrProperty as MyObject; 

This is just only an illustration, but I think you get the picture.

Answer 1

No, the FieldInfo represents attributes and metadata of a field in regards to a type. It is not attached to a specific instance. When you want to use it, you have to pass in the instance you want it to use (through GetValue or SetValue )

Answer 2

Despite the other answer saying no, this is possible.
I had the same problem and after some test I found this code to work:

Type oType = typeof(MyClass);
FieldInfo[] aoFieldInfo = oType.GetFields (BindingFlags.Public | BindingFlags.Static);

foreach (FieldInfo oFieldInfo in aoFieldInfo)
{
  object oValue = oFieldInfo.GetValue (null);
}

and it returns the values / objects of all members, of which I previously queried the FieldInfo .

Answer 3

I know this old but yes it is possible as long as you can have access to the instance of the parent object of the object in question...

for example:

public AxisObject getAxisObjectByName(string name)
    {
        FieldInfo[] Comboproperties = typeof(DrivesObject).GetFields();
        foreach (var property in Comboproperties)
        {
            if (property.Name == name)
            {
                return (AxisObject)property.GetValue(PersistantVariables.Instance.Drives);//pass the instance you're wanting to return child object instance from
            }
        }
        return null;
    }

Answer 4

I too was searching for this answer, found some inspiration in Tobias Knauss's answer.

Hopefully this helps someone as well.

With my fields placed in this Holiday class, I wanted to access them all in a collection.

    class Holiday
    {
        public static readonly DateTime New_Years_Day = new DateTime(year: DateTime.Now.AddYears(1).Year, month: 1, day: 1);
        public static readonly DateTime Christmas_Day = new DateTime(year: DateTime.Now.Year, month: 12, day: 24);
        public static readonly DateTime Thanksgiving_Day = new DateTime(year: DateTime.Now.Year, month: 11, day: 25);
        public static readonly DateTime Labor_Day = new DateTime(year: DateTime.Now.Year, month: 9, day: 6);
        public static readonly DateTime Memorial_Day = new DateTime(year: DateTime.Now.Year, month: 5, day: 31);
                                                                      

}

To test I created a method to run my test:

    static DateTime[] get_all_holidays()
    {  
        DateTime[] _holidays = 
            typeof(Holiday)
            .GetFields()
            .Select(s => 
                (DateTime)s.GetValue(null))
                .ToArray(); 

        foreach (DateTime holiday in _holidays)
        {
            Debug.WriteLine(holiday.ToString());

        }

        return _holidays;
    }

When I run the above code, I check my locals and see all the dates.

And finally implemented into a property for quick access:

    public static DateTime[] All_Holidays {
        get {
            return 
                typeof(Holiday)
                    .GetFields()
                    .Select(s =>
                        (DateTime)s.GetValue(null))
                        .ToArray();
        } }