Reflection and complex properties

Question

I have an object with primitive and complex properties.

I have to get property values by reflection.

I use this statements:

Dim propertyInfo As PropertyInfo = MYITEM.GetType().GetProperty("MyProp1")
Dim propertyValue As Object = propertyInfo.GetValue(MYITEM, Nothing)

and it'ok, but if I use the same code with complex property like this...

Dim propertyInfo As PropertyInfo = MYITEM.GetType().GetProperty("MyProp1.MyProp2")
Dim propertyValue As Object = propertyInfo.GetValue(MYITEM, Nothing)

the propertyInfo is null and I can't read the value of "MyProp2".

Exist an generic method to do this?

Answer 1

MyProp1.MyProp2 is not a property of your base object, MyProp1 is a property of that then MyProp2 is a property of the object returned by MyProp1.

Try this :

Dim propertyInfo1 As PropertyInfo = MYITEM.GetType().GetProperty("MyProp1") 
Dim propertyValue1 As Object = propertyInfo.GetValue(MYITEM, Nothing) 

Dim propertyInfo2 As PropertyInfo = propertyValue1.GetType().GetProperty("MyProp2") 
Dim propertyValue2 As Object = propertyInfo2.GetValue(propertyValue1, Nothing) 

You could try something like this extension method (sorry its in c#)

public static TRet GetPropertyValue<TRet>(this object obj, string propertyPathName)
    {
        if (obj == null)
        {
            throw new ArgumentNullException("obj");
        }

        string[] parts = propertyPathName.Split('.');
        string path = propertyPathName;
        object root = obj;

        if (parts.Length > 1)
        {
            path = parts[parts.Length - 1];
            parts = parts.TakeWhile((p, i) => i < parts.Length-1).ToArray();
            string path2 = String.Join(".", parts);
            root = obj.GetPropertyValue<object>(path2);
        }

        var sourceType = root.GetType();
        return (TRet)sourceType.GetProperty(path).GetValue(root, null);

    }

Then to test

public class Test1
{
    public Test1()
    {
        this.Prop1 = new Test2();
    }
    public Test2 Prop1 { get; set; }
}


public class Test2
{
    public Test2()
    {
        this.Prop2 = new Test3();
    }
    public Test3 Prop2 { get; set; }
}

public class Test3
{
    public Test3()
    {
        this.Prop3 = DateTime.Now.AddDays(-1); // Yesterday
    }
    public DateTime Prop3 { get; set; }
}

Usage

Test1 obj = new Test1();
var yesterday = obj.GetPropertyValue<DateTime>("Prop1.Prop2.Prop3");

Answer 2

If you're in a web project, or don't mind referencing System.Web, you could use:

object resolvedValue = DataBinder.Eval(object o, string propertyPath);

Which is simpler and has already been tested by Microsoft