Attributes, Caller Information and Reflection

Option Strict On

Imports System.ComponentModel

Public Class Early
End Class

<Assembly: System.Reflection.AssemblyMetadata("k", "v")>

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(8,1): error BC30637: Assembly or Module attribute statements must precede any declarations in a file.

<Version>2.1.0-beta.1</Version>
<AssemblyVersion>2.1.0.0</AssemblyVersion>
<Authors>Shelf team</Authors>
<Company>Shelf</Company>
<Product>Shelf catalogue</Product>
<Description>Library catalogue</Description>
<Copyright>Shelf</Copyright>
<SourceRevisionId>abc1234</SourceRevisionId>

Option Strict On

Imports System.Reflection
Imports System.Runtime.CompilerServices

Module Program
    Sub Main()
        Dim assembly As Assembly = GetType(Program).Assembly
        Console.WriteLine("AssemblyName.Version: " & assembly.GetName().Version.ToString())
        For Each data As CustomAttributeData In assembly.CustomAttributes.OrderBy(Function(d) d.AttributeType.Name)
            Dim arguments As String = String.Join(", ", data.ConstructorArguments.Select(Function(a) a.Value.ToString()))
            Console.WriteLine($"{data.AttributeType.Name,-40}{arguments}")
        Next
    End Sub
End Module

AssemblyName.Version: 2.1.0.0
AssemblyCompanyAttribute                Shelf
AssemblyConfigurationAttribute          Debug
AssemblyCopyrightAttribute              Shelf
AssemblyDescriptionAttribute            Library catalogue
AssemblyFileVersionAttribute            2.1.0.0
AssemblyInformationalVersionAttribute   2.1.0-beta.1+abc1234
AssemblyProductAttribute                Shelf catalogue
AssemblyTitleAttribute                  App
CompilationRelaxationsAttribute         8
DebuggableAttribute                     263
RuntimeCompatibilityAttribute
TargetFrameworkAttribute                .NETCoreApp,Version=v10.0

Option Strict On

Imports System.Reflection

<Assembly: AssemblyTitle("Shelf catalogue")>
<Assembly: AssemblyVersion("1.2.3.0")>

Module Program
    Sub Main()
        Console.WriteLine("built")
    End Sub
End Module

obj/Debug/net10.0/App.AssemblyInfo.vb(20,2): error BC30663: Attribute 'AssemblyTitleAttribute' cannot be applied multiple times.
obj/Debug/net10.0/App.AssemblyInfo.vb(21,2): error BC30663: Attribute 'AssemblyVersionAttribute' cannot be applied multiple times.

Option Strict On

Imports System.Reflection

Public Enum Audience
    Everyone
    Staff
    Admin
End Enum

<AttributeUsage(AttributeTargets.Class Or AttributeTargets.Method Or AttributeTargets.Property,
                AllowMultiple:=True, Inherited:=True)>
Public NotInheritable Class CatalogRuleAttribute
    Inherits Attribute

    Public ReadOnly Property Name As String
    Public Property Audience As Audience = Audience.Everyone
    Public Property Priority As Integer
    Public Property Tags As String()
    Public Property Handler As Type

    Public Sub New(name As String)
        Me.Name = name
    End Sub
End Class

<CatalogRule("NoDuplicates", Priority:=2, Audience:=Audience.Staff)>
<CatalogRule("MaxLoans", Tags:=New String() {"loans", "limits"}, Handler:=GetType(String))>
Public Class CatalogItem
    <CatalogRule("TitleRequired")>
    Public Overridable Property Title As String = ""

    <CatalogRule("OnlyAdmins", Audience:=Audience.Admin)>
    Public Overridable Sub Remove()
    End Sub
End Class

Public Class Magazine
    Inherits CatalogItem

    Public Overrides Sub Remove()
    End Sub

    Public Overrides Property Title As String
End Class

Module Program
    Sub Describe(label As String, rule As CatalogRuleAttribute)
        Dim tags As String = If(rule.Tags Is Nothing, "-", String.Join("/", rule.Tags))
        Dim handler As String = If(rule.Handler Is Nothing, "-", rule.Handler.Name)
        Console.WriteLine($"{label,-26}{rule.Name,-14}audience={rule.Audience,-9}priority={rule.Priority} tags={tags} handler={handler}")
    End Sub

    Sub Main()
        For Each rule As CatalogRuleAttribute In GetType(CatalogItem).GetCustomAttributes(GetType(CatalogRuleAttribute), False)
            Describe("CatalogItem", rule)
        Next
        For Each rule As CatalogRuleAttribute In GetType(Magazine).GetCustomAttributes(GetType(CatalogRuleAttribute), True)
            Describe("Magazine (inherit)", rule)
        Next
        Console.WriteLine("Magazine IsDefined (inherit False): " & GetType(Magazine).IsDefined(GetType(CatalogRuleAttribute), False))
        Console.WriteLine("Magazine IsDefined (inherit True):  " & GetType(Magazine).IsDefined(GetType(CatalogRuleAttribute), True))

        Dim removeDerived As MethodInfo = GetType(Magazine).GetMethod("Remove")
        Dim titleDerived As PropertyInfo = GetType(Magazine).GetProperty("Title")
        Console.WriteLine("Overriding method,   MemberInfo:       " & removeDerived.GetCustomAttributes(GetType(CatalogRuleAttribute), True).Length)
        Console.WriteLine("Overriding method,   Attribute class:  " & Attribute.GetCustomAttributes(removeDerived, GetType(CatalogRuleAttribute), True).Length)
        Console.WriteLine("Overriding property, MemberInfo:       " & titleDerived.GetCustomAttributes(GetType(CatalogRuleAttribute), True).Length)
        Console.WriteLine("Overriding property, Attribute class:  " & Attribute.GetCustomAttributes(titleDerived, GetType(CatalogRuleAttribute), True).Length)

        Dim titleRule As CatalogRuleAttribute = GetType(CatalogItem).GetProperty("Title").GetCustomAttribute(Of CatalogRuleAttribute)()
        Console.WriteLine("GetCustomAttribute(Of T): " & titleRule.Name)
        Try
            Dim ambiguous As CatalogRuleAttribute = GetType(CatalogItem).GetCustomAttribute(Of CatalogRuleAttribute)()
            Console.WriteLine(ambiguous.Name)
        Catch ex As AmbiguousMatchException
            Console.WriteLine("Two rules on one class: " & ex.GetType().Name)
        End Try
    End Sub
End Module

CatalogItem               NoDuplicates  audience=Staff    priority=2 tags=- handler=-
CatalogItem               MaxLoans      audience=Everyone priority=0 tags=loans/limits handler=String
Magazine (inherit)        NoDuplicates  audience=Staff    priority=2 tags=- handler=-
Magazine (inherit)        MaxLoans      audience=Everyone priority=0 tags=loans/limits handler=String
Magazine IsDefined (inherit False): False
Magazine IsDefined (inherit True):  True
Overriding method,   MemberInfo:       1
Overriding method,   Attribute class:  1
Overriding property, MemberInfo:       0
Overriding property, Attribute class:  1
GetCustomAttribute(Of T): TitleRequired
Two rules on one class: AmbiguousMatchException

Option Strict On

Imports System.ComponentModel

Public Class Computed
    Private Const Fixed As String = "fixed"
    Private Shared ReadOnly Dynamic As String = "dynamic"

    <Description(Fixed)>
    Public Property A As String

    <Description(Dynamic)>
    Public Property B As String

    <Description(String.Concat("a", "b"))>
    Public Property C As String

    <Description("a" & "b")>
    Public Property D As String

    <Description(NameOf(A))>
    Public Property E As String
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(12,18): error BC30059: Constant expression is required.
Program.vb(15,18): error BC30059: Constant expression is required.

Option Strict On

<AttributeUsage(AttributeTargets.Class)>
Public NotInheritable Class RuleAttribute
    Inherits Attribute

    Public ReadOnly Property Name As String
    Public Property Priority As Integer

    Public Sub New(name As String)
        Me.Name = name
    End Sub
End Class

<AttributeUsage(AttributeTargets.Class Or AttributeTargets.Method)>
Public NotInheritable Class AnyRuleAttribute
    Inherits Attribute
End Class

Public Class Plain
End Class

Option Strict On

Imports System.ComponentModel

<Rule("a"), Rule("b")>
Public Class Twice
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(5,13): error BC30663: Attribute 'RuleAttribute' cannot be applied multiple times.

Option Strict On

Imports System.ComponentModel

Public Class WrongTarget
    <Rule("a")>
    Public Sub Run()
    End Sub

    <Rule("b")>
    Public Property Title As String
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(6,6): error BC30662: Attribute 'RuleAttribute' cannot be applied to 'Run' because the attribute is not valid on this declaration type.
Program.vb(10,6): error BC30662: Attribute 'RuleAttribute' cannot be applied to 'Title' because the attribute is not valid on this declaration type.

Option Strict On

Imports System.ComponentModel

<Rule>
Public Class NoArgument
End Class

<Rule("a", "b")>
Public Class TooMany
End Class

<Rule("a", Missing:=1)>
Public Class UnknownNamed
End Class

<Rule("a", Name:="again")>
Public Class ReadOnlyNamed
End Class

<Rule(42)>
Public Class WrongType
End Class

<Rule("a", Priority:="high")>
Public Class WrongNamedType
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(5,2): error BC30455: Argument not specified for parameter 'name' of 'Public Sub New(name As String)'.
Program.vb(9,12): error BC30057: Too many arguments to 'Public Sub New(name As String)'.
Program.vb(13,12): error BC30661: Field or property 'Missing' is not found.
Program.vb(17,12): error BC31501: 'ReadOnly' attribute property 'Name' cannot be the target of an assignment.
Program.vb(21,7): error BC30512: Option Strict On disallows implicit conversions from 'Integer' to 'String'.
Program.vb(25,22): error BC30512: Option Strict On disallows implicit conversions from 'String' to 'Integer'.
Program.vb(25,22): error BC30934: Conversion from 'String' to 'Integer' cannot occur in a constant expression used as an argument to an attribute.

Option Strict On

<Plain>
Public Class AlsoNot
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(3,2): error BC31504: 'Plain' cannot be used as an attribute because it does not inherit from 'System.Attribute'.

Option Strict On

Imports System.ComponentModel

Public NotInheritable Class KindAttribute(Of T)
    Inherits Attribute
End Class

<Kind(Of Integer)>
Public Class UsesGeneric
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(9,2): error BC32066: Type arguments are not valid because attributes cannot be generic.

Option Strict On

Imports System.ComponentModel

Public Class Misplaced
    <Description("local")>
    Public Sub Run()
        <Description("x")> Dim local As Integer = 1
        Console.WriteLine(local)
    End Sub
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(8,9): error BC30660: Attributes cannot be applied to local variables.

Option Strict On

Imports System.ComponentModel

Public Class FieldTarget
    <field: NonSerialized>
    Public Property A As Integer
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(6,11): error BC30636: '>' expected.
Program.vb(6,13): error BC30188: Declaration expected.

Option Strict On

Imports System.ComponentModel

Public Class ReturnTarget
    <Return: Description("r")>
    Public Function F() As Integer
        Return 1
    End Function
End Class

Module Program
    Sub Main()
    End Sub
End Module

Program.vb(6,12): error BC30636: '>' expected.
Program.vb(6,14): error BC30188: Declaration expected.
Program.vb(6,6): error BC30183: Keyword is not valid as an identifier.

Option Strict On

Imports System.ComponentModel

Public Class Two
    <Description("a")> <Category("b")>
    Public Property A As Integer

    <Description("a"),
     Category("b")>
    Public Property B As Integer

    <Description("c"), Category("d")> Public Property C As Integer

    <Description("e") _
    > Public Property D As Integer
End Class

Module Program
    Sub Main()
        Console.WriteLine(GetType(Two).GetProperties().Length)
    End Sub
End Module

4

Option Strict On

Imports System.ComponentModel

Module Program
    <Obsolete("Use NewName", True)>
    Sub OldName()
    End Sub

    <Obsolete("Use NewName")>
    Sub OlderName()
    End Sub

    Sub Main()
        OldName()
        OlderName()
    End Sub
End Module

Program.vb(15,9): error BC30668: 'Public Sub OldName()' is obsolete: 'Use NewName'.
Program.vb(16,9): warning BC40000: 'Public Sub OlderName()' is obsolete: 'Use NewName'.

Option Strict On

Imports System.Runtime.CompilerServices

Module Program
    Sub WrongType(<CallerLineNumber> Optional line As String = "unset")
        Console.WriteLine("String parameter received: " & line)
    End Sub

    Sub WrongName(<CallerMemberName> Optional name As Integer = -1)
        Console.WriteLine("Integer parameter received: " & name)
    End Sub

    Sub Mandatory(<CallerMemberName> name As String)
        Console.WriteLine("Mandatory parameter received: " & name)
    End Sub

    Sub Main()
        WrongType()
        WrongName()
        Mandatory("typed")
    End Sub
End Module

String parameter received: unset
Integer parameter received: -1
Mandatory parameter received: typed

Trace()            ' member filled in, extra = 0
Trace(extra:=5)    ' member filled in, extra = 5
Trace("by hand")   ' the member name is the text you passed
Trace(, 7)         ' empty position: member filled in, extra = 7

member=Main extra=0
member=Main extra=5
member=typed by hand extra=0
member=Main extra=7

Option Strict On

Imports System.Runtime.CompilerServices

Public Class RuleViolationException
    Inherits Exception

    Public ReadOnly Property Expression As String

    Public Sub New(message As String, expression As String)
        MyBase.New(message)
        Me.Expression = expression
    End Sub
End Class

Module Guard
    Sub Require(condition As Boolean,
                <CallerArgumentExpression("condition")> Optional expression As String = Nothing)
        If Not condition Then
            Throw New RuleViolationException("Rule failed: " & expression, expression)
        End If
    End Sub

    Function Describe(value As Object,
                      <CallerArgumentExpression("value")> Optional expression As String = Nothing) As String
        Return $"{expression} = {value}"
    End Function
End Module

Module Program
    Sub Main()
        Dim copies As Integer = 3
        Dim title As String = "Dune"
        Console.WriteLine(Describe(copies))
        Console.WriteLine(Describe(copies * 2 + 1))
        Console.WriteLine(Describe(title.ToUpperInvariant()))
        Console.WriteLine(Describe(  copies   +   1  ))
        Console.WriteLine(Describe(
            copies))

        Try
            Require(copies > 5)
        Catch ex As RuleViolationException
            Console.WriteLine(ex.Message)
        End Try

        Try
            Require(title.Length = 0 OrElse copies < 0)
        Catch ex As RuleViolationException
            Console.WriteLine(ex.Message)
        End Try

        Try
            Dim missing As String = Nothing
            ArgumentNullException.ThrowIfNull(missing)
        Catch ex As ArgumentNullException
            Console.WriteLine(ex.Message.Replace(Environment.NewLine, " "))
        End Try

        Try
            ArgumentNullException.ThrowIfNull(Nothing, "explicit name")
        Catch ex As ArgumentNullException
            Console.WriteLine(ex.Message.Replace(Environment.NewLine, " "))
        End Try

        Try
            ArgumentException.ThrowIfNullOrEmpty(Nothing)
        Catch ex As ArgumentException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message.Replace(Environment.NewLine, " "))
        End Try
    End Sub
End Module

copies = 3
copies * 2 + 1 = 7
title.ToUpperInvariant() = DUNE
copies   +   1 = 4
copies = 3
Rule failed: copies > 5
Rule failed: title.Length = 0 OrElse copies < 0
Value cannot be null. (Parameter 'missing')
Value cannot be null. (Parameter 'explicit name')
ArgumentNullException: Value cannot be null. (Parameter 'Nothing')

Program.vb(12,45): warning BC42505: The CallerArgumentExpressionAttribute applied to parameter 'text' will have no effect. It is applied with an invalid parameter name.

Option Strict On

Imports System.Reflection

Public Enum LoanState
    Active = 1
    Returned = 2
End Enum

Public Interface IRenewable
    Sub Renew()
End Interface

Public MustInherit Class CatalogItem
    Public MustOverride Function Describe() As String
End Class

Public NotInheritable Class Magazine
    Inherits CatalogItem
    Implements IRenewable

    Public Overrides Function Describe() As String
        Return "magazine"
    End Function

    Public Sub Renew() Implements IRenewable.Renew
    End Sub
End Class

Public Structure Isbn
    Public Value As String
End Structure

Module Program
    Sub Row(label As String, type As Type)
        Console.WriteLine($"{label,-26}{type.Name,-14}class={type.IsClass,-6} value={type.IsValueType,-6} iface={type.IsInterface,-6} enum={type.IsEnum,-6} abstract={type.IsAbstract,-6} sealed={type.IsSealed,-6} generic={type.IsGenericType}")
    End Sub

    Sub Main()
        Dim item As CatalogItem = New Magazine()
        Dim ids As Object = 42

        Console.WriteLine("-- three ways to get a Type")
        Console.WriteLine("GetType(Magazine):          " & GetType(Magazine).Name)
        Console.WriteLine("item.GetType():             " & item.GetType().Name & "   (the run-time type)")
        Console.WriteLine("GetType(CatalogItem):       " & GetType(CatalogItem).Name & "   (the declared type)")
        Console.WriteLine("ids.GetType():              " & ids.GetType().FullName)
        Console.WriteLine("TypeOf item Is Magazine:    " & (TypeOf item Is Magazine))
        Console.WriteLine("TypeOf item Is IRenewable:  " & (TypeOf item Is IRenewable))
        Console.WriteLine("GetType(List(Of String)):   " & GetType(List(Of String)).ToString())
        Console.WriteLine("GetType(List(Of )):         " & GetType(List(Of )).ToString())
        Console.WriteLine("GetType(Dictionary(Of ,)):  " & GetType(Dictionary(Of ,)).ToString())
        Console.WriteLine("GetType(Integer()):         " & GetType(Integer()).ToString())
        Console.WriteLine("GetType(Integer):           " & GetType(Integer).FullName)

        Console.WriteLine("-- what a Type can tell you")
        Row("Magazine", GetType(Magazine))
        Row("CatalogItem", GetType(CatalogItem))
        Row("IRenewable", GetType(IRenewable))
        Row("LoanState", GetType(LoanState))
        Row("Isbn", GetType(Isbn))
        Row("Integer", GetType(Integer))
        Row("List(Of String)", GetType(List(Of String)))
        Row("String", GetType(String))

        Console.WriteLine("-- relations")
        Console.WriteLine("Magazine.BaseType:          " & GetType(Magazine).BaseType.Name)
        Console.WriteLine("Isbn.BaseType:              " & GetType(Isbn).BaseType.Name)
        Console.WriteLine("LoanState.BaseType:         " & GetType(LoanState).BaseType.Name)
        Console.WriteLine("Magazine interfaces:        " & String.Join(", ", GetType(Magazine).GetInterfaces().Select(Function(i) i.Name)))
        Console.WriteLine("IRenewable.IsAssignableFrom(Magazine): " & GetType(IRenewable).IsAssignableFrom(GetType(Magazine)))
        Console.WriteLine("CatalogItem.IsAssignableFrom(Magazine): " & GetType(CatalogItem).IsAssignableFrom(GetType(Magazine)))
        Console.WriteLine("Magazine.IsSubclassOf(CatalogItem):    " & GetType(Magazine).IsSubclassOf(GetType(CatalogItem)))
        Console.WriteLine("LoanState names: " & String.Join(", ", [Enum].GetNames(GetType(LoanState))))
        Console.WriteLine("List(Of String) type arguments: " & GetType(List(Of String)).GetGenericArguments()(0).Name)

        Console.WriteLine("-- the assembly")
        Dim assembly As Assembly = GetType(Program).Assembly
        Console.WriteLine("Name:         " & assembly.GetName().Name)
        Console.WriteLine("Entry point:  " & assembly.EntryPoint.DeclaringType.Name & "." & assembly.EntryPoint.Name)
        Console.WriteLine("Same as GetExecutingAssembly: " & (assembly Is Assembly.GetExecutingAssembly()))
        Console.WriteLine("Same as GetEntryAssembly:     " & (assembly Is Assembly.GetEntryAssembly()))
        Console.WriteLine("Exported types: " & String.Join(", ", assembly.GetExportedTypes().Select(Function(t) t.Name).OrderBy(Function(n) n)))
        Console.WriteLine("All types:      " & String.Join(", ", assembly.GetTypes().Select(Function(t) t.Name).OrderBy(Function(n) n)))
        Console.WriteLine("References:     " & String.Join(", ", assembly.GetReferencedAssemblies().Select(Function(r) r.Name).OrderBy(Function(n) n)))
    End Sub
End Module

-- three ways to get a Type
GetType(Magazine):          Magazine
item.GetType():             Magazine   (the run-time type)
GetType(CatalogItem):       CatalogItem   (the declared type)
ids.GetType():              System.Int32
TypeOf item Is Magazine:    True
TypeOf item Is IRenewable:  True
GetType(List(Of String)):   System.Collections.Generic.List`1[System.String]
GetType(List(Of )):         System.Collections.Generic.List`1[T]
GetType(Dictionary(Of ,)):  System.Collections.Generic.Dictionary`2[TKey,TValue]
GetType(Integer()):         System.Int32[]
GetType(Integer):           System.Int32
-- what a Type can tell you
Magazine                  Magazine      class=True   value=False  iface=False  enum=False  abstract=False  sealed=True   generic=False
CatalogItem               CatalogItem   class=True   value=False  iface=False  enum=False  abstract=True   sealed=False  generic=False
IRenewable                IRenewable    class=False  value=False  iface=True   enum=False  abstract=True   sealed=False  generic=False
LoanState                 LoanState     class=False  value=True   iface=False  enum=True   abstract=False  sealed=True   generic=False
Isbn                      Isbn          class=False  value=True   iface=False  enum=False  abstract=False  sealed=True   generic=False
Integer                   Int32         class=False  value=True   iface=False  enum=False  abstract=False  sealed=True   generic=False
List(Of String)           List`1        class=True   value=False  iface=False  enum=False  abstract=False  sealed=False  generic=True
String                    String        class=True   value=False  iface=False  enum=False  abstract=False  sealed=True   generic=False
-- relations
Magazine.BaseType:          CatalogItem
Isbn.BaseType:              ValueType
LoanState.BaseType:         Enum
Magazine interfaces:        IRenewable
IRenewable.IsAssignableFrom(Magazine): True
CatalogItem.IsAssignableFrom(Magazine): True
Magazine.IsSubclassOf(CatalogItem):    True
LoanState names: Active, Returned
List(Of String) type arguments: String
-- the assembly
Name:         App
Entry point:  Program.Main
Same as GetExecutingAssembly: True
Same as GetEntryAssembly:     True
Exported types: CatalogItem, IRenewable, Isbn, LoanState, Magazine
All types:      _Closure$__, CatalogItem, IRenewable, Isbn, LoanState, Magazine, Program
References:     Microsoft.VisualBasic.Core, System.Collections, System.Console, System.Linq, System.Runtime

Option Strict On

Imports System.Reflection

Public Class Cover
    Public Event Opened As EventHandler
End Class

Public Class Book
    Private WithEvents Front As New Cover()

    Public Property Title As String = ""
    Public ReadOnly Property Pages As Integer

    Public Event Borrowed As EventHandler
    Public Event Returned(sender As Object, e As EventArgs)

    Default Public ReadOnly Property Item(index As Integer) As Char
        Get
            Return Title(index)
        End Get
    End Property

    Public Function Count(Optional step1 As Integer = 1) As Integer
        Static calls As Integer
        calls += step1
        Return calls
    End Function

    Public Function Match(ParamArray tags As String()) As Integer
        Dim wanted As Integer = tags.Length
        Dim filter As Func(Of String, Boolean) = Function(tag) tag.Length = wanted
        Return tags.Count(filter)
    End Function

    Private Sub Front_Opened(sender As Object, e As EventArgs) Handles Front.Opened
    End Sub
End Class

Module Helpers
    Public Sub Hello()
    End Sub
End Module

Module Program
    Sub List(type As Type)
        Console.WriteLine("== " & type.Name)
        Dim flags As BindingFlags = BindingFlags.Instance Or BindingFlags.Static Or BindingFlags.Public Or BindingFlags.NonPublic Or BindingFlags.DeclaredOnly
        For Each member As MemberInfo In type.GetMembers(flags).OrderBy(Function(m) m.MemberType.ToString()).ThenBy(Function(m) m.Name)
            Console.WriteLine($"  {member.MemberType,-12}{member.Name}")
        Next
    End Sub

    Sub Main()
        List(GetType(Book))
        Console.WriteLine("== nested types of Book")
        For Each nested As Type In GetType(Book).GetNestedTypes(BindingFlags.NonPublic Or BindingFlags.Public)
            Console.WriteLine("  " & nested.Name)
        Next
        Console.WriteLine("== Helpers (a Module)")
        Dim helpers As Type = GetType(Helpers)
        Console.WriteLine($"  IsAbstract={helpers.IsAbstract} IsSealed={helpers.IsSealed}")
        For Each data As CustomAttributeData In helpers.CustomAttributes
            Console.WriteLine("  attribute: " & data.AttributeType.Name)
        Next
        Console.WriteLine("== attributes behind VB syntax")
        For Each data As CustomAttributeData In GetType(Book).GetMethod("Match").GetParameters()(0).CustomAttributes
            Console.WriteLine("  ParamArray parameter: " & data.AttributeType.Name)
        Next
        For Each data As CustomAttributeData In GetType(Book).CustomAttributes
            Console.WriteLine("  Book: " & data.AttributeType.Name & " " & String.Join(",", data.ConstructorArguments.Select(Function(a) a.Value)))
        Next
    End Sub
End Module

== Book
  Constructor .ctor
  Event       Borrowed
  Event       Returned
  Field       _Front
  Field       _Pages
  Field       _Title
  Field       $STATIC$Count$20188$calls
  Field       BorrowedEvent
  Field       ReturnedEvent
  Method      add_Borrowed
  Method      add_Returned
  Method      Count
  Method      Front_Opened
  Method      get_Front
  Method      get_Item
  Method      get_Pages
  Method      get_Title
  Method      Match
  Method      remove_Borrowed
  Method      remove_Returned
  Method      set_Front
  Method      set_Title
  NestedType  _Closure$__24-0
  NestedType  ReturnedEventHandler
  Property    Front
  Property    Item
  Property    Pages
  Property    Title
== nested types of Book
  ReturnedEventHandler
  _Closure$__24-0
== Helpers (a Module)
  IsAbstract=False IsSealed=True
  attribute: StandardModuleAttribute
== attributes behind VB syntax
  ParamArray parameter: ParamArrayAttribute
  Book: DefaultMemberAttribute Item

Option Strict On

Imports System.Reflection

Public Class Book
    Private _isbn As String = "978-0-00-000000-2"
    Public Property Title As String
    Public Shared Property Created As Integer

    Public Sub New(title As String)
        Me.Title = title
        Created += 1
    End Sub

    Public Sub Rename(newTitle As String)
        If String.IsNullOrWhiteSpace(newTitle) Then Throw New ArgumentException("Title is empty", NameOf(newTitle))
        Title = newTitle
    End Sub

    Public Sub Rename(newTitle As String, upperCase As Boolean)
        Title = If(upperCase, newTitle.ToUpperInvariant(), newTitle)
    End Sub

    Public Function Wrap(Of T)(value As T) As String
        Return "[" & value.ToString() & "]"
    End Function
End Class

Module Program
    Sub Main()
        Dim bookType As Type = GetType(Book)

        Console.WriteLine("-- looking types up by name")
        Console.WriteLine("Type.GetType(""Book"")          = " & If(Type.GetType("Book") Is Nothing, "Nothing", "found"))
        Console.WriteLine("Type.GetType(""ShelfApp.Book"") = " & If(Type.GetType("ShelfApp.Book") Is Nothing, "Nothing", "found"))
        Console.WriteLine("FullName                       = " & bookType.FullName)

        Console.WriteLine("-- creating objects")
        Dim book As Book = CType(Activator.CreateInstance(bookType, "Dune"), Book)
        Dim constructor As ConstructorInfo = bookType.GetConstructor(New Type() {GetType(String)})
        Dim second As Book = CType(constructor.Invoke(New Object() {"Emma"}), Book)
        Console.WriteLine($"{book.Title}, {second.Title}, created={Book.Created}")
        Try
            Dim noDefault As Object = Activator.CreateInstance(bookType)
        Catch ex As MissingMethodException
            Console.WriteLine("No parameterless constructor: " & ex.GetType().Name)
        End Try

        Console.WriteLine("-- invoking members")
        Try
            bookType.GetMethod("Rename")
        Catch ex As AmbiguousMatchException
            Console.WriteLine("GetMethod(""Rename"") with two overloads: " & ex.GetType().Name)
        End Try
        Dim rename1 As MethodInfo = bookType.GetMethod("Rename", New Type() {GetType(String)})
        Dim rename2 As MethodInfo = bookType.GetMethod("Rename", New Type() {GetType(String), GetType(Boolean)})
        rename1.Invoke(book, New Object() {"Dune Messiah"})
        rename2.Invoke(book, New Object() {"children of dune", True})
        Console.WriteLine("Title now " & book.Title)

        Dim titleProperty As PropertyInfo = bookType.GetProperty("Title")
        titleProperty.SetValue(book, "God Emperor")
        Console.WriteLine("Property read: " & CStr(titleProperty.GetValue(book)))

        Dim isbnField As FieldInfo = bookType.GetField("_isbn", BindingFlags.Instance Or BindingFlags.NonPublic)
        Console.WriteLine("Private field: " & CStr(isbnField.GetValue(book)))
        Console.WriteLine("Shared property: " & CInt(bookType.GetProperty("Created").GetValue(Nothing)))

        Try
            rename1.Invoke(book, New Object() {" "})
        Catch ex As TargetInvocationException
            Console.WriteLine("Wrapped: " & ex.GetType().Name & " -> " & ex.InnerException.GetType().Name)
        End Try
        Try
            rename1.Invoke(book, New Object() {42})
        Catch ex As ArgumentException
            Console.WriteLine("Wrong argument type: " & ex.GetType().Name)
        End Try

        Console.WriteLine("-- generics")
        Dim listType As Type = GetType(List(Of )).MakeGenericType(GetType(Book))
        Console.WriteLine(listType.ToString())
        Dim list As Object = Activator.CreateInstance(listType)
        listType.GetMethod("Add").Invoke(list, New Object() {book})
        Console.WriteLine("Count = " & CInt(listType.GetProperty("Count").GetValue(list)))
        Dim wrap As MethodInfo = bookType.GetMethod("Wrap").MakeGenericMethod(GetType(Integer))
        Console.WriteLine(CStr(wrap.Invoke(book, New Object() {42})))

        Console.WriteLine("-- a delegate removes the per-call cost")
        Dim getTitle As Func(Of Book, String) = CType(titleProperty.GetGetMethod().CreateDelegate(GetType(Func(Of Book, String))), Func(Of Book, String))
        Console.WriteLine(getTitle(book))
    End Sub
End Module

-- looking types up by name
Type.GetType("Book")          = Nothing
Type.GetType("ShelfApp.Book") = found
FullName                       = ShelfApp.Book
-- creating objects
Dune, Emma, created=2
No parameterless constructor: MissingMethodException
-- invoking members
GetMethod("Rename") with two overloads: AmbiguousMatchException
Title now CHILDREN OF DUNE
Property read: God Emperor
Private field: 978-0-00-000000-2
Shared property: 2
Wrapped: TargetInvocationException -> ArgumentException
Wrong argument type: ArgumentException
-- generics
System.Collections.Generic.List`1[ShelfApp.Book]
Count = 1
[42]
-- a delegate removes the per-call cost
God Emperor

Option Strict On

Public Interface IExporter
    Function Export(titles As IEnumerable(Of String)) As String
End Interface

<AttributeUsage(AttributeTargets.Class, AllowMultiple:=False)>
Public NotInheritable Class ExporterAttribute
    Inherits Attribute

    Public ReadOnly Property Format As String

    Public Sub New(format As String)
        Me.Format = format
    End Sub
End Class

Option Strict On

Imports Shelf.Contracts

<Exporter("csv")>
Public Class CsvExporter
    Implements IExporter

    Public Function Export(titles As IEnumerable(Of String)) As String Implements IExporter.Export
        Return String.Join(",", titles)
    End Function
End Class

<Exporter("lines")>
Public Class LineExporter
    Implements IExporter

    Public Function Export(titles As IEnumerable(Of String)) As String Implements IExporter.Export
        Return String.Join(" | ", titles.Select(Function(t, i) $"{i + 1}. {t}"))
    End Function
End Class

Public Class NotAnExporter
End Class

Friend Class HiddenExporter
    Implements IExporter

    Public Function Export(titles As IEnumerable(Of String)) As String Implements IExporter.Export
        Return "hidden"
    End Function
End Class

<ItemGroup>
  <ProjectReference Include="..\Contracts\Contracts.vbproj" />
  <ProjectReference Include="..\Plugin\Plugin.vbproj" ReferenceOutputAssembly="false" />
</ItemGroup>
<Target Name="CopyPlugin" AfterTargets="Build">
  <Copy SourceFiles="..\Plugin\bin\$(Configuration)\$(TargetFramework)\Plugin.dll" DestinationFolder="$(OutDir)plugins" />
</Target>

Option Strict On

Imports System.IO
Imports System.Reflection
Imports System.Runtime.CompilerServices
Imports System.Runtime.Loader
Imports Shelf.Contracts

Module Program
    <MethodImpl(MethodImplOptions.NoInlining)>
    Function RunPlugin(path As String) As WeakReference
        Dim context As New AssemblyLoadContext("plugins", isCollectible:=True)
        Dim assembly As Assembly = context.LoadFromAssemblyPath(path)
        Console.WriteLine("Loaded " & assembly.GetName().Name & " into context " & context.Name)

        Dim titles As String() = {"Dune", "Emma", "Ulysses"}
        For Each type As Type In assembly.GetTypes().OrderBy(Function(t) t.Name)
            Dim implementsExporter As Boolean = GetType(IExporter).IsAssignableFrom(type)
            Dim attribute As ExporterAttribute = type.GetCustomAttribute(Of ExporterAttribute)()
            Console.WriteLine($"{type.Name,-14} IExporter={implementsExporter,-5} public={type.IsPublic,-5} attribute={If(attribute Is Nothing, "none", attribute.Format)}")
            If implementsExporter AndAlso attribute IsNot Nothing Then
                Dim exporter As IExporter = CType(Activator.CreateInstance(type), IExporter)
                Console.WriteLine("   -> " & exporter.Export(titles))
            End If
        Next

        Dim weak As New WeakReference(context)
        context.Unload()
        Return weak
    End Function

    Sub Main()
        Dim path As String = System.IO.Path.Combine(AppContext.BaseDirectory, "plugins", "Plugin.dll")
        Console.WriteLine("Plugin file exists: " & File.Exists(path))
        Dim weak As WeakReference = RunPlugin(path)
        For attempt As Integer = 1 To 10
            If Not weak.IsAlive Then Exit For
            GC.Collect()
            GC.WaitForPendingFinalizers()
        Next
        Console.WriteLine("Context collected after unload: " & Not weak.IsAlive)
    End Sub
End Module

Plugin file exists: True
Loaded Plugin into context plugins
_Closure$__    IExporter=False public=False attribute=none
CsvExporter    IExporter=True  public=True  attribute=csv
   -> Dune,Emma,Ulysses
HiddenExporter IExporter=True  public=False attribute=none
LineExporter   IExporter=True  public=True  attribute=lines
   -> 1. Dune | 2. Emma | 3. Ulysses
NotAnExporter  IExporter=False public=True  attribute=none
Context collected after unload: True

Option Strict On

Imports System.Diagnostics.CodeAnalysis

Public Class CsvExporter
    Public Function Export() As String
        Return "csv"
    End Function
End Class

Module Program
    <RequiresUnreferencedCode("Creates a type from its name")>
    Function CreateByName(name As String) As Object
        Return Activator.CreateInstance(Type.GetType(name))
    End Function

    Function CreateKnown(<DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)> type As Type) As Object
        Return Activator.CreateInstance(type)
    End Function

    Function CreateUnannotated(type As Type) As Object
        Return Activator.CreateInstance(type)
    End Function

    Sub Main()
        Dim known As Object = CreateKnown(GetType(CsvExporter))
        Dim byName As Object = CreateByName("ShelfApp.CsvExporter")
        Dim unannotated As Object = CreateUnannotated(GetType(CsvExporter))
        Console.WriteLine(known.GetType().Name & " " & byName.GetType().Name & " " & unannotated.GetType().Name)
    End Sub
End Module

<RuntimeIdentifier>linux-arm64</RuntimeIdentifier>
<SelfContained>true</SelfContained>
<PublishTrimmed>true</PublishTrimmed>
<EnableTrimAnalyzer>true</EnableTrimAnalyzer>

Program.vb(22,9): Trim analysis warning IL2067: ShelfApp.Program.CreateUnannotated(Type): 'type' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicParameterlessConstructor' in call to 'System.Activator.CreateInstance(Type)'. The parameter 'type' of method 'ShelfApp.Program.CreateUnannotated(Type)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
Program.vb(27,13): Trim analysis warning IL2026: ShelfApp.Program.Main(): Using member 'ShelfApp.Program.CreateByName(String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creates a type from its name.
CsvExporter CsvExporter CsvExporter

Program.vb(22,9): Trim analysis error IL2067: ShelfApp.Program.CreateUnannotated(Type): 'type' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicParameterlessConstructor' in call to 'System.Activator.CreateInstance(Type)'. The parameter 'type' of method 'ShelfApp.Program.CreateUnannotated(Type)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
Program.vb(27,13): Trim analysis error IL2026: ShelfApp.Program.Main(): Using member 'ShelfApp.Program.CreateByName(String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creates a type from its name.
/root/.nuget/packages/microsoft.net.illink.tasks/10.0.13/build/Microsoft.NET.ILLink.targets(103,5): error NETSDK1144: Optimizing assemblies for size failed.

Program.vb(22): Trim analysis warning IL2067: ShelfApp.Program.CreateUnannotated(Type): 'type' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicParameterlessConstructor' in call to 'System.Activator.CreateInstance(Type)'. The parameter 'type' of method 'ShelfApp.Program.CreateUnannotated(Type)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
Program.vb(27): Trim analysis warning IL2026: ShelfApp.Program.Main(): Using member 'ShelfApp.Program.CreateByName(String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creates a type from its name.
CsvExporter CsvExporter CsvExporter