Reflection and property enumeration

[balabaster]

okay, I'm trying to reference a property within a class using a string "class.property", I've got a test class, imaginitively called "Test", hold your applause...it's got a property called value.

I've got a function called GetValue that accepts an array of objects and a string for the property reference I want to get the value of.

Now I can use reflection to create a type and use the GetProperty method to reference the "value" property:

This gets a dynamic object of type "Test":

Dim MyClass As Type = GetType(Test)

at which point, I can use MyClass.GetProperty("Value") to grab the property's value and return it...seems simple enough.

Okay, lets add some complexity. Given that I can pass an array of objects into my function, I want to be able to give a fully qualified property name to reference:

Lets say there's two classes, I want to specify which class to pass the value back from:

Dim Args(1) As Object
Args(0) = New Test1(123.45)
Args(1) = New Test2(987.65)
Dim Value = GetValue(Args, "Test1.Value")

I think I could do this readily enough if I could pass a string value into GetType (which obviously I can't)... rather than code a switch/case to pass the correct type given a string, is there an easy way to evaluate a string as the type it refers to rather than as a string?

(Apologies for not using code tags, the new code windows are a touch excessive for small code blocks)

[Plater]

Wait, why can't you use:
Type.GetType(string name)
?
Granted you would need to do a .Split('.') of some sort to get your type?

Type tt = Type.GetType("WMI.WebDownload");
object o = tt.InvokeMember("WebDownload", BindingFlags.CreateInstance, null, null, new object[] { "http://www.google.com", @"c:\ggg.html" });
tt.InvokeMember("GetWebObject", BindingFlags.Default|BindingFlags.InvokeMethod, null, o, null);
 

I have a namespace called "WMI" and a class called "WebDownload" in it. For my purpose I needed to create an instance of the class (The first InvokeMember() call, the object[] is the constructors arguments) and assigned it to object o. I then used the second InvokeMethod to invoke the method "GetWebObject", which has no arguments, but I told it to invoke that method on object o. Since o is of type WebDownload, it executed my code. I check with breakpoints and it really does enter into that function.

Somewhere in all of that should be an idea to help you out? You could apply the same logic as the BindingFlags.InvokeMethod call, only change the flags to be like "return property" or whatever they are

[balabaster]

hehe, I'd forgotten I'd posted this. So, here was my solution... for the moment. I'm going to design something recursive in the long run, but this was my prototype:

Function GetValue(ByVal MyInstance As IMyInterface, ByVal ValuePath As String) As Double
 
    Dim AssemblyName As String = Reflection.Assembly.GetExecutingAssembly().GetName.Name
    Dim PathNodes As List(Of String) = ValuePath.Split(".").ToList
 
    If PathNodes(0) <> AssemblyName Then PathNodes.Insert(0, AssemblyName)
 
    Dim CrntInstance As Object = MyInstance
 
    For i As Integer = 2 To PathNodes.Count - 1
 
        Dim CrntType As Type = CrntInstance.GetType()
        Dim CrntProperty As String = PathNodes(i)
        Dim dynProperty As Reflection.PropertyInfo = CrntType.GetProperty(CrntProperty)
        Dim CrntValue = dynProperty.GetValue(CrntInstance, _
                                       System.Reflection.BindingFlags.GetProperty, _
                                       Nothing, _
                                       Nothing, _
                                       Nothing)
        CrntInstance = CrntValue
 
    Next
 
    Return CrntInstance
 
End Function

I'm not sure I like the use of Split() to do it... but I can't think of anything more appropriate.