C# Using Reflection to Get a Generic Object's (and its Nested Objects) Properties

Question

This is a scenario created to help understand what Im trying to achieve.

I am trying to create a method that returns the specified property of a generic object

e.g.

public object getValue<TModel>(TModel item, string propertyName) where TModel : class{
    PropertyInfo p = typeof(TModel).GetProperty(propertyName);
    return p.GetValue(item, null);
}

The code above works fine if you're looking for a property on the TModel item e.g.

string customerName = getValue<Customer>(customer, "name");

However, if you want to find out what the customer's group's name is, it becomes a problem: e.g.

string customerGroupName = getValue<Customer>(customer, "Group.name");

Hoping someone can give me some insight on this way out scenario - thanks.

Answer 1

Here's a simple method that uses recursion to solve your problem. It allows you to traverse an object graph by passing a "dotted" property name. It works with properties as well as fields.

static class PropertyInspector 
{
    public static object GetObjectProperty(object item,string property)
    {
        if (item == null)
            return null;

        int dotIdx = property.IndexOf('.');

        if (dotIdx > 0)
        {
            object obj = GetObjectProperty(item,property.Substring(0,dotIdx));

            return GetObjectProperty(obj,property.Substring(dotIdx+1));
        }

        PropertyInfo propInfo = null;
        Type objectType = item.GetType();

        while (propInfo == null && objectType != null)
        {
            propInfo = objectType.GetProperty(property, 
                      BindingFlags.Public 
                    | BindingFlags.Instance 
                    | BindingFlags.DeclaredOnly);

            objectType = objectType.BaseType;
        }

        if (propInfo != null)
            return propInfo.GetValue(item, null);

        FieldInfo fieldInfo = item.GetType().GetField(property, 
                      BindingFlags.Public | BindingFlags.Instance);

        if (fieldInfo != null)
            return fieldInfo.GetValue(item);

        return null;
    }
}

Example:

class Person
{
   public string Name { get; set; }
   public City City { get; set; }
}

class City
{
   public string Name { get; set; }
   public string ZipCode { get; set; }
}

Person person = GetPerson(id);

Console.WriteLine("Person name = {0}", 
      PropertyInspector.GetObjectProperty(person,"Name"));

Console.WriteLine("Person city = {0}",
      PropertyInspector.GetObjectProperty(person,"City.Name"));