Question:
I have this C# program, that gets the value of field tablename of mytable.
And it works fine.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
namespace AttachObjectsCS
{
static class Program
{
public class cmytable
{
public string tablename = "test";
}
// http://stackoverflow.com/questions/2616638/access-the-value-of-a-member-expression
private static object GetValue(System.Linq.Expressions.MemberExpression member)
{
System.Linq.Expressions.Expression objectMember = System.Linq.Expressions.Expression.Convert(member, typeof(object));
System.Linq.Expressions.Expression<Func<object>> getterLambda = System.Linq.Expressions.Expression.Lambda<Func<object>>(objectMember);
var getter = getterLambda.Compile();
return getter();
}
public static void AddField<T>(System.Linq.Expressions.Expression<Func<T>> expr, string alias)
{
var body = ((System.Linq.Expressions.MemberExpression)expr.Body);
Console.WriteLine("Name is: {0}", body.Member.Name);
object obj = GetValue(body);
Console.WriteLine("Value is: {0}", obj);
}
/// <summary>
/// Der Haupteinstiegspunkt für die Anwendung.
/// </summary>
[STAThread]
static void Main()
{
if (false)
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
cmytable mytable = new cmytable();
AddField(() => mytable.tablename, "te");
Console.WriteLine(Environment.NewLine);
Console.WriteLine(" --- Press any key to continue --- ");
Console.ReadKey();
} // End Sub Main
} // End Class Program
} // End Namespace AttachObjectsCS
Now I need the same functionality in VB.NET, but it fails.
Now since I'm aware that VB.NET and C# don't always use the same linq expression, I'm not surprised that I run into a problem here.
Module Program
Public Class cmytable
Public tablename As String = "test"
End Class
Public Sub AddField(Of T)(expr As System.Linq.Expressions.Expression(Of Func(Of T)))
Dim body = DirectCast(expr.Body, System.Linq.Expressions.MemberExpression)
Dim strName As String = body.Member.Name
Console.WriteLine("Name is: {0}", strName)
Dim obj As Object = GetValue(body)
Console.WriteLine("Value is: {0}", obj)
End Sub
' http://stackoverflow.com/questions/2616638/access-the-value-of-a-member-expression '
Private Function GetValue(member As System.Linq.Expressions.MemberExpression) As Object
Dim objectMember As System.Linq.Expressions.Expression = System.Linq.Expressions.Expression.Convert(member, GetType(Object))
Dim getterLambda As System.Linq.Expressions.Expression(Of Func(Of Object)) = System.Linq.Expressions.Expression.Lambda(Of Func(Of Object))(objectMember)
Dim getter = getterLambda.Compile()
Return getter()
End Function
Public Sub Main()
Dim mytable As New cmytable
AddField(Function() mytable.tablename)
End Sub
End Module ' Program
The problem is in GetValue, and the problem is that I don't seem to have the proper objectMember.
Here the debug output for the expressions:
CS objectMember = {Convert(value(AttachObjectsCS.Program+<>c__DisplayClass0).mytable.tablename)}
VB objectMember = {Convert(value(AttachObjects.Program+_Closure$__1).$VB$Local_mytable.tablename)}
CS getterLambda = {() => Convert(value(AttachObjectsCS.Program+<>c__DisplayClass0).mytable.tablename)}
VB getterLambda = {() => Convert(value(AttachObjects.Program+_Closure$__1).$VB$Local_mytable.tablename)}
My guess would be that the problem is the $VB$Local_ in $VB$Local_mytable.tablename
Now I'm wondering what I have to change for this to work in VB.NET.
Anybody knows / has a clue ?
Edit:
Ah, the problem seems to be caused by "Option Infer Off" in the project wide settings.
So the the question alters and becomes: How to do this with "Option Infer Off" ?
