Cast a property to its actual type dynamically using reflection

Question

I need to cast a property to its actual type dynamically. How do I/Can I do this using reflection?

To explain the real scenario that I am working on a bit. I am tryi

Answer 1

I had some time so I tried to solve my problem using VS2010 and I think I was right previously when I though that the dynamic keywork would 'solve' my question. See the code below.

using System.Reflection;

namespace TempTest
{
    public class ClassA
    {
        public int IntProperty { get; set; }
    }

    public class ClassB
    {
        public ClassB()
        {
            MyProperty = new ClassA { IntProperty = 4 };
        }
        public ClassA MyProperty { get; set; }
    }

    public class Program
    {
        static void Main(string[] args)
        {
            ClassB tester = new ClassB();

            PropertyInfo propInfo = typeof(ClassB).GetProperty("MyProperty");
            //get a type unsafe reference to ClassB`s property
            dynamic property = propInfo.GetValue(tester, null);

            //casted the property to its actual type dynamically
            int result = property.IntProperty; 
        }
    }
}

Answer 2

Though I should post the solution to the real world problem.

string objectType = "MyProperty";

using (MyEntitiesContext entitiesContext = new MyEntitiesContext())
{
try
{
    string queryString = @"SELECT VALUE " + objectType+  " FROM MyEntitiesContext." + objectType + " AS " + objectType + " WHERE " + objectType + ".id = @id";

    IQueryable<Object> query = entitiesContext.CreateQuery<Object>(queryString, new ObjectParameter("id", objectId));

    foreach (Object result in query)
    {
        return result;
    }
}
catch (EntitySqlException ex)
{
    Console.WriteLine(ex.ToString());
}
}

return null;

I think the new CLR4 dynamic keywork might be the "nice" solution.

Thanks for all the responces.

Answer 3

Once you get the reflected type, you can use Convert.ChangeType().

Answer 4

public object CastPropertyValue(PropertyInfo property, string value) { 
if (property == null || String.IsNullOrEmpty(value))
    return null;
if (property.PropertyType.IsEnum)
{
    Type enumType = property.PropertyType;
    if (Enum.IsDefined(enumType, value))
        return Enum.Parse(enumType, value);
}
if (property.PropertyType == typeof(bool))
    return value == "1" || value == "true" || value == "on" || value == "checked";
else if (property.PropertyType == typeof(Uri))
    return new Uri(Convert.ToString(value));
else
    return Convert.ChangeType(value, property.PropertyType);  }

Answer 5

Having a variable of a specific type is really only useful at compile time, and will not help you at runtime in using it in this way. Try to write the code where you would utilize this... you'll find that it keeps pushing the requirement to know the type to compile time at some level (maybe further up the call chain, but you'll still eventually need to type the concrete type for this to be useful).

One thing to keep in mind, though - if your type is a reference type, the object is still truly the type you've created. It's not like there is a benefit to having the object saved as your type vs. object. This is the beauty of reflection (as well as part of why it works). There really is no reason to try to "change" it's type at runtime in a cast, since it's still going to be an object.

Answer 6

How about setting the root value as a string and then carry it around as a string until you need to convert it to the target type?