使用反射从复杂类中获取值

Question

I have a class, which is created and populated from an xml string, I've simplified it for example purposes:

[XmlRoot("Person")]
public sealed class Person
{
    [XmlElement("Name")]
    public string Name { get; set; }

    [XmlElement("Location")]
    public string Location { get; set; }

    [XmlElement("Emails", Type = typeof(PersonEmails)]
    public PersonEmails Emails { get; set; }
}

public class PersonEmails
{
    [XmlElement("Email", Type = typeof(PersonEmail))]
    public PersonEmail[] Emails { get; set; }
}

public class PersonEmail
{
    [XmlAttribute("Type")]
    public string Type { get; set; }

    [XmlText]
    public string Value { get; set; }
}

To extract the information, I'm trying to load them into another class, which is simply:

public class TransferObject
{
    public string Name { get; set; }

    public ObjectField[] Fields { get; set; }
}

public class ObjectField
{
    public string Name { get; set; }
    public string Value { get; set; }
}

I'm only populating "Fields" from the other object, which would simply be (Name = "Location", Value = "London"), but for Emails, (Name = "Email"+Type, Value = jeff@here.com)

Currently I can populate all the other fields, but I'm stuck with Emails, and knowing how to dig deep enough to be able to use reflection (or not) to get the information I need. Currently I'm using:

Person person = Person.FromXmlString(xmlString);
List<ObjectField> fields = new List<ObjectField>();
foreach (PropertyInfo pinfo in person.getType().GetProperties()
{
    fields.Add(new ObjectField { Name = pinfo.Name, Value = pinfo.getValue(person, null).ToString();
}

How can I expand on the above to add all my emails to the list?

Answer 1

You are trying to type cast a complex values type to string value so you lost the data. Instead use following code:

class Program
{
    static void Main(string[] args)
    {
        Person person = new Person();
        person.Name = "Person One";
        person.Location = "India";
        person.Emails = new PersonEmails();
        person.Phones = new PersonPhones();
        person.Emails.Emails = new PersonEmail[] { new PersonEmail() { Type = "Official", Value = "xyz@official.com" }, new PersonEmail() { Type = "Personal", Value = "xyz@personal.com" } };
        person.Phones.Phones = new PersonPhone[] { new PersonPhone() { Type = "Official", Value = "789-456-1230" }, new PersonPhone() { Type = "Personal", Value = "123-456-7890" } };

        List<ObjectField> fields = new List<ObjectField>();

        fields = GetPropertyValues(person);

    }

    static List<ObjectField> GetPropertyValues(object obj)
    {
        List<ObjectField> propList = new List<ObjectField>();

        foreach (PropertyInfo pinfo in obj.GetType().GetProperties())
        {
            var value = pinfo.GetValue(obj, null);

            if (pinfo.PropertyType.IsArray)
            {
                var arr = value as object[];
                for (var i = 0; i < arr.Length; i++)
                {
                    if (arr[i].GetType().IsPrimitive)
                    {
                        propList.Add(new ObjectField() { Name = pinfo.Name + i.ToString(), Value = arr[i].ToString() });
                    }
                    else
                    {
                        var lst = GetPropertyValues(arr[i]);
                        if (lst != null && lst.Count > 0)
                            propList.AddRange(lst);
                    }
                }
            }
            else
            {
                if (pinfo.PropertyType.IsPrimitive || value.GetType() == typeof(string))
                {
                    propList.Add(new ObjectField() { Name = pinfo.Name, Value = value.ToString() });
                }
                else
                {
                    var lst = GetPropertyValues(value);
                    if (lst != null && lst.Count > 0)
                        propList.AddRange(lst);
                }
            }
        }
        return propList;
    }
}

Answer 2

Check this snippet out:

if(pinfo.PropertyType.IsArray)
{
  // Grab the actual instance of the array.
  // We'll have to use it in a few spots.
  var array = pinfo.GetValue(personObject);

  // Get the length of the array and build an indexArray.
  int length = (int)pinfo.PropertyType.GetProperty("Length").GetValue(array);

  // Get the "GetValue" method so we can extact the array values
  var getValue = findGetValue(pinfo.PropertyType);

  // Cycle through each index and use our "getValue" to fetch the value from the array.
  for(int i=0; i<length; i++)
    fields.Add(new ObjectField { Name = pinfo.Name, Value = getValue.Invoke(array, new object[]{i}).ToString();
}

// Looks for the "GetValue(int index)" MethodInfo.
private static System.Reflection.MethodInfo findGetValue(Type t)
{
  return (from mi in t.GetMethods()
    where mi.Name == "GetValue"
    let parms = mi.GetParameters()
    where parms.Length == 1
    from p in parms
    where p.ParameterType == typeof(int)
    select mi).First();
}

You can definately do it with Reflection ... You can take advantage of the fact that a Type can tell you if it's an array or not ( IsArray )... and then take advantage of the fact that an Array has a method GetValue(int index) that will give you a value back.

Per your comment

Because Emails is a property within a different class, recursion should be used. However the trick is knowing when to go to the next level. Really that is up to you, but if it were me, I would use some sort of Attribute :

static void fetchProperties(Object instance, List<ObjectField> fields)
{
  foreach(var pinfo in instance.GetType().GetProperties())
  {
    if(pinfo.PropertyType.IsArray)
    {
      ... // Code described above
    }
    else if(pinfo.PropertyType.GetCustomAttributes(typeof(SomeAttribute), false).Any())
      // Go the next level
      fetchProperties(pinfo.GetValue(instance), fields);
    else
    {
      ... // Do normal code
    }

  }
}