Accessing a Collection Through Reflection

Question

Is there a way to iterate (through foreach preferably) over a collection using reflection? I\'m iterating over the properties in an object using reflection, and when the pr

Answer 1

Just get the value of the property and then cast it into an IEnumerable. Here is some (untested) code to give you an idea:

ClassWithListProperty obj = new ClassWithListProperty();
obj.List.Add(1);
obj.List.Add(2);
obj.List.Add(3);

Type type = obj.GetType();
PropertyInfo listProperty = type.GetProperty("List", BindingFlags.Public);
IEnumerable listObject = (IEnumerable) listProperty.GetValue(obj, null);

foreach (int i in listObject)
    Console.Write(i); // should print out 123

Answer 2

The best you could probably do would be to check if the object implements certain collection interfaces - probably IEnumerable would be all that you need. Then it's just a matter of calling GetEnumerator() off of the object, and using IEnumerator.MoveNext() and IEnumerator.Current to work your way through the collection.

This won't help you if the collection doesn't implement those interfaces, but if that's the case it's not really much of a collection, I suppose.

Answer 3

A rather straightforward approach would be to type cast the object as the collection and directly use that.

Answer 4

Just for information may be it will be of someone's help... I had a class with nested classes and collection of some other classes. I wanted to save the property values of the class as well nested classes and collection of classes. My code is as follows:

 public void LogObject(object obj, int indent)
    {
        if (obj == null) return;
        string indentString = new string(' ', indent);
        Type objType = obj.GetType();
        PropertyInfo[] properties = objType.GetProperties();

        foreach (PropertyInfo property in properties)
        {
            Type tColl = typeof(ICollection<>);
            Type t = property.PropertyType;
            string name = property.Name;


            object propValue = property.GetValue(obj, null); 
            //check for nested classes as properties
            if (property.PropertyType.Assembly == objType.Assembly)
            {
                string _result = string.Format("{0}{1}:", indentString, property.Name);
                log.Info(_result);
                LogObject(propValue, indent + 2);
            }
            else
            {
                string _result = string.Format("{0}{1}: {2}", indentString, property.Name, propValue);
                log.Info(_result);
            }

            //check for collection
            if (t.IsGenericType && tColl.IsAssignableFrom(t.GetGenericTypeDefinition()) ||
                t.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == tColl))
            {
                //var get = property.GetGetMethod();
                IEnumerable listObject = (IEnumerable)property.GetValue(obj, null);
                if (listObject != null)
                {
                    foreach (object o in listObject)
                    {
                        LogObject(o, indent + 2);
                    }
                }
            }
        }
    }

An called this function

LogObject(obj, 0);

However, I have some structs inside my classes and I need to figure out how to get their values. Moreoevr, I have some LIst. I need to get their value as well.... I will post if I update my code.

Answer 5

I had this issue, but instead of using reflection, i ended up just checking if it was IEnumerable. All collections implement that.

if (item is IEnumerable)
{
    foreach (object o in (item as IEnumerable))
    {

    }
} else {
   // reflect over item
}

Answer 6

When your using reflection you aren't necessarily using an instance of that object. You would have to create an instance of that type of be able to iterate through the object's properties. So if you are using reflection use the ConstructorInfo.Invoke() (?) method to create a new instance or point to an instance of the type.