Early and Late Binding

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <RootNamespace>LateApp</RootNamespace>
    <OptionExplicit>On</OptionExplicit>
    <OptionStrict>On</OptionStrict>
    <OptionInfer>On</OptionInfer>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <NuGetAudit>false</NuGetAudit>
  </PropertyGroup>
</Project>

Option Strict On

Module Program
    Sub Main()
        Console.WriteLine("-- early binding")
        EarlyBinding.Run()
        Console.WriteLine("-- CallByName under Option Strict On")
        CallByNameDemo.Run()
        Console.WriteLine("-- reflection under Option Strict On")
        ReflectionDemo.Run()
        Console.WriteLine("-- late binding (LateBinding.vb)")
        LateBinding.Run()
        Console.WriteLine("-- relative cost, one million calls")
        Performance.Run()
        Console.WriteLine("-- a typed facade over the late-bound file")
        Console.WriteLine(LateBinding.DescribeAny(New Book("Emma", 1815, Isbn.Parse("9780306406157"), New Author("Jane Austen"))))
        Console.WriteLine(LateBinding.DescribeAny(New Magazine("Byte", 1982, 7)))
    End Sub
End Module

Option Strict On

Module Program
    Sub Main()
        Dim item As Object = "text"
        Console.WriteLine(item.Length)
        item.Trim()
        Dim n As Object = item(0)
    End Sub
End Module

Program.vb(6,27): error BC30574: Option Strict On disallows late binding.
Program.vb(7,9): error BC30574: Option Strict On disallows late binding.
Program.vb(8,27): error BC30574: Option Strict On disallows late binding.

Option Strict On

Module Program
    Sub Main()
        Dim rounded As Integer = 3.7
        Dim parsed As Double = "3.5"
        Dim shown As String = 42
        Dim number As Integer = "12"
    End Sub
End Module

Program.vb(5,34): error BC30512: Option Strict On disallows implicit conversions from 'Double' to 'Integer'.
Program.vb(6,32): error BC30512: Option Strict On disallows implicit conversions from 'String' to 'Double'.
Program.vb(7,31): error BC30512: Option Strict On disallows implicit conversions from 'Integer' to 'String'.
Program.vb(8,33): error BC30512: Option Strict On disallows implicit conversions from 'String' to 'Integer'.

Option Strict On
Option Infer Off

Module Program
    Sub Main()
        Dim x = 1
        Dim y
    End Sub
End Module

Program.vb(6,13): error BC30209: Option Strict On requires all variable declarations to have an 'As' clause.
Program.vb(7,13): error BC30209: Option Strict On requires all variable declarations to have an 'As' clause.
Program.vb(7,13): warning BC42024: Unused local variable: 'y'.

Option Strict On

Module Program
    Function Twice(n As Integer)
        Return n * 2
    End Function

    ReadOnly Property Label
        Get
            Return "x"
        End Get
    End Property

    Sub Main()
    End Sub
End Module

Program.vb(4,14): error BC30210: Option Strict On requires all Function, Property, and Operator declarations to have an 'As' clause.
Program.vb(8,23): error BC30210: Option Strict On requires all Function, Property, and Operator declarations to have an 'As' clause.

Option Strict On

Module Program
    Sub Main()
        Dim a As Object = 1
        Dim b As Object = 2
        Console.WriteLine(a + b)
        Console.WriteLine(a = b)
        Console.WriteLine(a < b)
        Console.WriteLine(a And b)
    End Sub
End Module

Program.vb(7,27): error BC30038: Option Strict On prohibits operands of type Object for operator '+'.
Program.vb(7,31): error BC30038: Option Strict On prohibits operands of type Object for operator '+'.
Program.vb(8,27): error BC32013: Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity.
Program.vb(8,31): error BC32013: Option Strict On disallows operands of type Object for operator '='. Use the 'Is' operator to test for object identity.
Program.vb(9,27): error BC30038: Option Strict On prohibits operands of type Object for operator '<'.
Program.vb(9,31): error BC30038: Option Strict On prohibits operands of type Object for operator '<'.
Program.vb(10,27): error BC30038: Option Strict On prohibits operands of type Object for operator 'And'.
Program.vb(10,33): error BC30038: Option Strict On prohibits operands of type Object for operator 'And'.

Option Strict On

Module Program
    Sub Main()
        Dim items As Object = New Integer() {1, 2}
        For Each n In items
            Console.WriteLine(n)
        Next
        For Each n As Integer In items
            Console.WriteLine(n)
        Next
    End Sub
End Module

Program.vb(6,23): error BC32023: Expression is of type 'Object', which is not a collection type.
Program.vb(9,34): error BC32023: Expression is of type 'Object', which is not a collection type.

Option Strict On

Module Program
    Sub Main()
        Dim book As Object = New System.Text.StringBuilder()
        book.Append("x")
        Dim d As New System.Collections.Hashtable()
        Dim v As Integer = d("k")
    End Sub
End Module

Program.vb(6,9): error BC30574: Option Strict On disallows late binding.
Program.vb(8,28): error BC30512: Option Strict On disallows implicit conversions from 'Object' to 'Integer'.

Option Strict On

Module EarlyBinding
    Sub Run()
        Dim isbn As Isbn = Isbn.Parse("9780306406157")
        Dim book As New Book("Dune", 1965, isbn, New Author("Frank Herbert"))

        ' Every member is resolved by the compiler against the static type.
        Console.WriteLine(book.Title)
        book.Title = "Dune Messiah"
        Console.WriteLine(book.Describe())

        ' Through the base class: the call is still bound at compile time (a virtual call).
        Dim item As CatalogItem = book
        Console.WriteLine(item.Describe())

        ' An Object variable needs a cast to get early binding back.
        Dim anything As Object = book
        Dim asBook As Book = DirectCast(anything, Book)
        Console.WriteLine(asBook.Kind)
        Dim asMagazine As Magazine = TryCast(anything, Magazine)
        Console.WriteLine(asMagazine Is Nothing)
        Try
            Dim wrong As Magazine = DirectCast(anything, Magazine)
            Console.WriteLine(wrong.IssueNumber)
        Catch ex As InvalidCastException
            Console.WriteLine(ex.Message)
        End Try
        If TypeOf anything Is CatalogItem Then
            Console.WriteLine(DirectCast(anything, CatalogItem).Year)
        End If
    End Sub
End Module

Dune
Book: Dune Messiah (1965) by Frank Herbert
Book: Dune Messiah (1965) by Frank Herbert
Book
True
Unable to cast object of type 'LateApp.Book' to type 'LateApp.Magazine'.
1965

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <RootNamespace>ErrorsApp</RootNamespace>
    <OptionStrict>Off</OptionStrict>
    <AdditionalOptions>-optionstrict:custom</AdditionalOptions>
    <NoWarn>1701</NoWarn>
    <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
  </PropertyGroup>
</Project>

Option Infer Off

Module Program
    Function Twice(n As Integer)
        Return n * 2
    End Function

    Sub Main()
        Dim x = 1
        Dim rounded As Integer = 3.7
        Dim item As Object = "text"
        Console.WriteLine(item.Length)
        Dim a As Object = 1
        Dim b As Object = 2
        Console.WriteLine(a + b)
        Console.WriteLine(a = b)
        Console.WriteLine(a < b)
        Console.WriteLine(a And b)
    End Sub
End Module

Program.vb(4,14): warning BC42021: Function without an 'As' clause; return type of Object assumed.
Program.vb(9,13): warning BC42020: Variable declaration without an 'As' clause; type of Object assumed.
Program.vb(10,34): warning BC42016: Implicit conversion from 'Double' to 'Integer'.
Program.vb(12,27): warning BC42017: Late bound resolution; runtime errors could occur.
Program.vb(15,27): warning BC42019: Operands of type Object used for operator '+'; runtime errors could occur.
Program.vb(15,31): warning BC42019: Operands of type Object used for operator '+'; runtime errors could occur.
Program.vb(16,27): warning BC42018: Operands of type Object used for operator '='; use the 'Is' operator to test object identity.
Program.vb(16,31): warning BC42018: Operands of type Object used for operator '='; use the 'Is' operator to test object identity.
Program.vb(17,27): warning BC42019: Operands of type Object used for operator '<'; runtime errors could occur.
Program.vb(17,31): warning BC42019: Operands of type Object used for operator '<'; runtime errors could occur.
Program.vb(18,27): warning BC42019: Operands of type Object used for operator 'And'; runtime errors could occur.
Program.vb(18,33): warning BC42019: Operands of type Object used for operator 'And'; runtime errors could occur.

Option Strict On

Imports Microsoft.VisualBasic

Public Class Printer
    Public Property Prefix As String = ">"

    Public Function Show(value As Integer) As String
        Return Prefix & " Integer " & value.ToString()
    End Function

    Public Sub Increment(ByRef value As Integer)
        value += 1
    End Sub

    Private Function Hidden() As String
        Return "hidden"
    End Function

    Public Sub Fail()
        Throw New InvalidOperationException("boom")
    End Sub

    Public Function Pad(value As String, width As Integer) As String
        Return value.PadLeft(width, "."c)
    End Function
End Class

Module CallByNameDemo
    Sub Run()
        Dim book As New Book("Dune", 1965, Isbn.Parse("9780306406157"), New Author("Frank Herbert"))

        ' CallType.Get reads a property, CallType.Let / Set writes it, CallType.Method calls a method.
        Console.WriteLine(CallByName(book, "Title", CallType.Get))
        CallByName(book, "Title", CallType.Let, "Dune Messiah")
        Console.WriteLine(CallByName(book, "Describe", CallType.Method))

        ' Names can come from data; the result type is Object, so convert it.
        Dim printer As New Printer()
        Dim shown As String = CStr(CallByName(printer, "Show", CallType.Method, 7))
        Console.WriteLine(shown)
        Console.WriteLine(CallByName(printer, "Pad", CallType.Method, "7", 4))

        ProbeCreateObject()

        ' Member names are matched without regard to case, and non-public members are not found.
        Console.WriteLine(CallByName(book, "TITLE", CallType.Get))
        Try
            Console.WriteLine(CallByName(printer, "Hidden", CallType.Method))
        Catch ex As MissingMemberException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        ' An exception thrown by the target arrives as itself, not wrapped.
        Try
            CallByName(printer, "Fail", CallType.Method)
        Catch ex As InvalidOperationException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        Dim memberNames As String() = {"Kind", "Year", "Missing"}
        For Each memberName In memberNames
            Try
                Console.WriteLine(memberName & " = " & CStr(CallByName(book, memberName, CallType.Get)))
            Catch ex As MissingMemberException
                Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
            End Try
        Next
    End Sub

#Disable Warning CA1416 ' CreateObject is Windows-only; this probe exists to show the failure elsewhere
    Sub ProbeCreateObject()
        Try
            Dim fso As Object = CreateObject("Scripting.FileSystemObject")
            Console.WriteLine(CStr(CallByName(fso, "GetFileName", CallType.Method, "C:\data\books.txt")))
        Catch ex As Exception
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try
    End Sub
#Enable Warning CA1416
End Module

Dune
Book: Dune Messiah (1965) by Frank Herbert
> Integer 7
...7
Exception: Cannot create ActiveX component.
Dune Messiah
MissingMemberException: Public member 'Hidden' on type 'Printer' not found.
InvalidOperationException: boom
Kind = Book
Year = 1965
MissingMemberException: Public member 'Missing' on type 'Book' not found.

Option Strict On

Imports System.Reflection

Module ReflectionDemo
    Sub Run()
        Dim book As New Book("Dune", 1965, Isbn.Parse("9780306406157"), New Author("Frank Herbert"))
        Dim bookType As Type = book.GetType()

        ' The same lookups, written with reflection. Nothing here is late bound.
        Dim title As PropertyInfo = bookType.GetProperty("Title")
        Console.WriteLine(title.GetValue(book))
        title.SetValue(book, "Dune Messiah")
        Console.WriteLine(bookType.GetMethod("Describe").Invoke(book, Nothing))
        Console.WriteLine(bookType.InvokeMember("Year", BindingFlags.GetProperty, Nothing, book, Nothing))

        ' A missing member returns Nothing from GetMethod instead of throwing at the call.
        Console.WriteLine(bookType.GetMethod("Missing") Is Nothing)

        ' Reflection is case sensitive unless you ask otherwise, and it wraps exceptions.
        Console.WriteLine(bookType.GetProperty("title") Is Nothing)
        Console.WriteLine(bookType.GetProperty("title", BindingFlags.Public Or BindingFlags.Instance Or BindingFlags.IgnoreCase) Is Nothing)
        Dim printer As New Printer()
        Try
            GetType(Printer).GetMethod("Fail").Invoke(printer, Nothing)
        Catch ex As TargetInvocationException
            Console.WriteLine(ex.GetType().Name & " -> " & ex.InnerException.GetType().Name)
        End Try

        ' Look up once, then call through a typed delegate: the fast form of the same idea.
        Dim getter As Func(Of Book, String) = DirectCast(
            System.Delegate.CreateDelegate(GetType(Func(Of Book, String)), bookType.GetProperty("Title").GetGetMethod()),
            Func(Of Book, String))
        Console.WriteLine(getter(book))
    End Sub
End Module

Dune
Book: Dune Messiah (1965) by Frank Herbert
1965
True
True
False
TargetInvocationException -> InvalidOperationException
Dune Messiah

' LateBinding.vb: the ONLY file in this project with Option Strict Off.
' Everything else, including the project itself, uses Option Strict On.
Option Strict Off

Imports System.Dynamic
Imports Microsoft.VisualBasic

Friend Module LateBinding
    ' The typed facade: callers see strict, early-bound signatures.
    Public Function DescribeAny(item As Object) As String
        Return item.Kind & " -> " & item.Describe()
    End Function

    Public Function LateAddLoop(target As Object, count As Integer) As Integer
        Dim last As Integer
        For i = 1 To count
            last = target.Bump()
        Next
        Return last
    End Function

    Public Sub Run()
        Dim item As Object = New Book("Dune", 1965, Isbn.Parse("9780306406157"), New Author("Frank Herbert"))

        ' Property get, property set and method call on an Object variable.
        Console.WriteLine(item.Title)
        item.Title = "Dune Messiah"
        Console.WriteLine(item.Describe())
        Console.WriteLine(item.Authors.Count)
        Console.WriteLine(item.Authors(0).Name)
        Console.WriteLine(item.TITLE)

        ' An exception thrown by the target arrives as itself.
        Try
            Dim failing As Object = New Printer()
            failing.Fail()
        Catch ex As InvalidOperationException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        ' The compiler cannot see the members, so the run-time binder looks them up.
        Try
            Console.WriteLine(item.Pages)
        Catch ex As MissingMemberException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        Try
            item.Rewind(3)
        Catch ex As MissingMemberException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        ' A Nothing receiver fails at run time too.
        Dim nobody As Object = Nothing
        Try
            Console.WriteLine(nobody.ToString())
        Catch ex As NullReferenceException
            Console.WriteLine(ex.GetType().Name)
        End Try

        ' Overloads are chosen from the run-time types of the arguments.
        Dim printer As Object = New Printer()
        Dim small As Object = CShort(7)
        Console.WriteLine(printer.Show(small))
        Dim text As Object = "8"
        Console.WriteLine(printer.Show(text))
        Try
            Console.WriteLine(printer.Show("nine"))
        Catch ex As InvalidCastException
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        ' Named arguments work too.
        Console.WriteLine(printer.Pad(width:=6, value:="x"))

        ' ByRef arguments are copied back into the caller's variable after the late call.
        Dim counter As Integer = 1
        printer.Increment(counter)
        Console.WriteLine(counter)

        ' Setting a field of a boxed structure through an Object variable.
        Dim corner As Object = New Point2D()
        corner.X = 10
        corner.Y = 20
        Console.WriteLine(corner.X & "," & corner.Y)

        ' Assigning to a field of a structure that is itself the result of a late-bound read is refused.
        Dim holder As Object = New Corner()
        Try
            holder.Position.X = 5
        Catch ex As Exception
            Console.WriteLine(ex.GetType().Name & ": " & ex.Message)
        End Try

        ' Operators on Object operands are resolved at run time as well.
        Dim a As Object = 10
        Dim b As Object = "2.5"
        Console.WriteLine(a + b)
        Console.WriteLine(a & b)
        Console.WriteLine(a > b)
        Console.WriteLine((a + b).GetType().Name)

        ' Turning the switch off also allows implicit narrowing and string-to-number conversions.
        Dim rounded As Integer = 3.7
        Dim parsed As Double = "3.5"
        Dim shown As String = 42
        Console.WriteLine(rounded & " " & parsed & " " & shown)

        ' Dynamic objects: IDynamicMetaObjectProvider is honoured by the Visual Basic late binder.
        Dim bag As Object = New ExpandoObject()
        bag.Title = "Emma"
        bag.Pages = 474
        Console.WriteLine(bag.Title & " " & bag.Pages)

        Dim settings As Object = New SettingsBag()
        settings.Theme = "dark"
        Console.WriteLine(settings.THEME)

        ' DynamicObject.TryInvokeMember answers calls; a member read without parentheses tries the
        ' call first, so it reaches TryInvokeMember when the class overrides it.
        Dim recorder As Object = New Recorder()
        Console.WriteLine(recorder.Open("a", 2))
        Console.WriteLine(recorder.Status)

        ' A type parameter must be boxed to an Object variable first to be used late-bound.
        Console.WriteLine(LengthOf("hello"))
        Console.WriteLine(LengthOf(New Integer() {1, 2, 3}))

        ' COM automation is late bound through CreateObject; the Windows branch is not run here.
        If OperatingSystem.IsWindows() Then
            Dim excel As Object = CreateObject("Excel.Application")
            excel.Visible = False
            Dim workbook As Object = excel.Workbooks.Add()
            workbook.Worksheets(1).Cells(1, 1).Value = "Shelf"
            workbook.Close(False)
            excel.Quit()
        Else
            Console.WriteLine("COM automation needs Windows; skipped on " & Runtime.InteropServices.RuntimeInformation.OSDescription.Split(" "c)(0))
        End If
    End Sub

    Private Function LengthOf(Of T)(value As T) As Integer
        Dim boxed As Object = value
        Return boxed.Length
    End Function
End Module

Dune
Book: Dune Messiah (1965) by Frank Herbert
1
Frank Herbert
Dune Messiah
InvalidOperationException: boom
MissingMemberException: Public member 'Pages' on type 'Book' not found.
MissingMemberException: Public member 'Rewind' on type 'Book' not found.
NullReferenceException
> Integer 7
> Integer 8
InvalidCastException: Conversion from string "nine" to type 'Integer' is not valid.
.....x
2
10,20
Exception: Late-bound assignment to a field of value type 'Point2D' is not valid when 'Point2D' is the result of a late-bound expression.
12.5
102.5
True
Double
4 3.5 42
Emma 474
dark
Open(a, 2)
Status()
5
3
COM automation needs Windows; skipped on Ubuntu

Book -> Book: Emma (1815) by Jane Austen
Magazine -> Magazine: Byte (1982)

Option Strict On

Imports System.Dynamic

' A dynamic property bag written under Option Strict On. Late-bound callers can read and write
' its members by name because it implements IDynamicMetaObjectProvider through DynamicObject.
Public Class SettingsBag
    Inherits DynamicObject

    Private ReadOnly _values As New Dictionary(Of String, Object)(StringComparer.OrdinalIgnoreCase)

    Public Overrides Function TryGetMember(binder As GetMemberBinder, ByRef result As Object) As Boolean
        Return _values.TryGetValue(binder.Name, result)
    End Function

    Public Overrides Function TrySetMember(binder As SetMemberBinder, value As Object) As Boolean
        _values(binder.Name) = value
        Return True
    End Function
End Class

' A bag that answers every method call; it also answers a plain member read, as the call
' to a method with no arguments.
Public Class Recorder
    Inherits DynamicObject

    Public Overrides Function TryInvokeMember(binder As InvokeMemberBinder, args() As Object, ByRef result As Object) As Boolean
        result = binder.Name & "(" & String.Join(", ", args) & ")"
        Return True
    End Function

    Public Overrides Function TryGetMember(binder As GetMemberBinder, ByRef result As Object) As Boolean
        result = "get " & binder.Name
        Return True
    End Function
End Class


Public Class Cell
    Public Property Value As Integer
    Public Function Bump() As Integer
        Value += 1
        Return Value
    End Function
End Class

Public Structure Point2D
    Public X As Integer
    Public Y As Integer
End Structure

Public Class Corner
    Public Property Position As Point2D
End Class

Option Strict On

Imports System.Diagnostics
Imports System.Reflection
Imports Microsoft.VisualBasic

Module Performance
    Private Const Iterations As Integer = 1000000

    Private Function Measure(label As String, work As Func(Of Integer)) As Double
        work() ' warm up
        Dim watch = Stopwatch.StartNew()
        Dim result = work()
        watch.Stop()
        Console.WriteLine(label.PadRight(28) & result.ToString().PadLeft(8) & "  " & (watch.Elapsed.TotalMilliseconds).ToString("F1").PadLeft(8) & " ms")
        Return watch.Elapsed.TotalMilliseconds
    End Function

    Sub Run()
        Dim cell As New Cell()
        Dim bump As MethodInfo = GetType(Cell).GetMethod("Bump")
        Dim typed As Func(Of Integer) = Function() As Integer
                                           cell.Value = 0
                                           Dim last As Integer
                                           For i = 1 To Iterations
                                               last = cell.Bump()
                                           Next
                                           Return last
                                       End Function
        Dim viaCallByName As Func(Of Integer) = Function() As Integer
                                                    cell.Value = 0
                                                    Dim last As Integer
                                                    For i = 1 To Iterations
                                                        last = CInt(CallByName(cell, "Bump", CallType.Method))
                                                    Next
                                                    Return last
                                                End Function
        Dim viaReflection As Func(Of Integer) = Function() As Integer
                                                    cell.Value = 0
                                                    Dim last As Integer
                                                    For i = 1 To Iterations
                                                        last = CInt(bump.Invoke(cell, Nothing))
                                                    Next
                                                    Return last
                                                End Function
        Dim viaDelegate As Func(Of Integer) = Function() As Integer
                                                  cell.Value = 0
                                                  Dim call1 = DirectCast(System.Delegate.CreateDelegate(GetType(Func(Of Integer)), cell, bump), Func(Of Integer))
                                                  Dim last As Integer
                                                  For i = 1 To Iterations
                                                      last = call1()
                                                  Next
                                                  Return last
                                              End Function
        Dim viaLate As Func(Of Integer) = Function() As Integer
                                              cell.Value = 0
                                              Return LateBinding.LateAddLoop(cell, Iterations)
                                          End Function

        Dim baseline = Measure("early bound call", typed)
        Dim t1 = Measure("CallByName", viaCallByName)
        Dim t2 = Measure("MethodInfo.Invoke", viaReflection)
        Dim t3 = Measure("cached typed delegate", viaDelegate)
        Dim t4 = Measure("late bound (Object)", viaLate)
        Console.WriteLine("late / early ratio: " & (t4 / baseline).ToString("F0") & "x (varies by machine)")
    End Sub
End Module

early bound call             1000000       6.9 ms
CallByName                   1000000     329.2 ms
MethodInfo.Invoke            1000000      28.4 ms
cached typed delegate        1000000       9.4 ms
late bound (Object)          1000000     328.2 ms
late / early ratio: 48x (varies by machine)

dotnet publish -r linux-arm64 -p:PublishTrimmed=true -p:TreatWarningsAsErrors=false -o out

LateBinding.vb(26,9): Trim analysis warning IL2026: LateApp.LateBinding.Run(): Using member 'Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object, Type, String, Object[], String[], Type[], Boolean[])' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Late binding is dynamic and cannot be statically analyzed. The referenced types and members may be trimmed.
LateBinding.vb(27,9): Trim analysis warning IL2026: LateApp.LateBinding.Run(): Using member 'Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateSet(Object, Type, String, Object[], String[], Type[])' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Late binding is dynamic and cannot be statically analyzed. The referenced types and members may be trimmed.
LateBinding.vb(28,9): Trim analysis warning IL2026: LateApp.LateBinding.Run(): Using member 'Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object, Type, String, Object[], String[], Type[], Boolean[])' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Late binding is dynamic and cannot be statically analyzed. The referenced types and members may be trimmed.
LateBinding.vb(99,9): Trim analysis warning IL2026: LateApp.LateBinding.Run(): Using member 'Microsoft.VisualBasic.CompilerServices.Operators.AddObject(Object, Object)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The object types cannot be statically analyzed so their operators may be trimmed.
CallByNameDemo.vb(74,17): Trim analysis warning IL2026: LateApp.CallByNameDemo.ProbeCreateObject(): Using member 'Microsoft.VisualBasic.Interaction.CreateObject(String, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. The COM object to be created cannot be statically analyzed and may be trimmed.
ReflectionDemo.vb(11,13): Trim analysis warning IL2075: LateApp.ReflectionDemo.Run(): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicProperties' in call to 'System.Type.GetProperty(String)'. The return value of method 'System.Object.GetType()' 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.

-- early binding
Dune
Book: Dune Messiah (1965) by Frank Herbert
Book: Dune Messiah (1965) by Frank Herbert
Book
True
Unable to cast object of type 'LateApp.Book' to type 'LateApp.Magazine'.
1965
-- CallByName under Option Strict On
Dune
Book: Dune Messiah (1965) by Frank Herbert
Unhandled exception. System.MissingMemberException: Public member 'Show' on type 'Printer' not found.

using System.Dynamic;
using Microsoft.CSharp.RuntimeBinder;
using Shelf.Core;

// C# dynamic: the same late binding idea, resolved by the C# run-time binder.
dynamic item = new Book("Dune", 1965, Isbn.Parse("9780306406157"), new Author("Frank Herbert"));
Console.WriteLine(item.Title);
item.Title = "Dune Messiah";
Console.WriteLine(item.Describe());
Console.WriteLine(item.Authors[0].Name);

try
{
    Console.WriteLine(item.Pages);
}
catch (RuntimeBinderException ex)
{
    Console.WriteLine(ex.GetType().Name + ": " + ex.Message);
}

dynamic bag = new ExpandoObject();
bag.Title = "Emma";
bag.Pages = 474;
Console.WriteLine(bag.Title + " " + bag.Pages);

dynamic a = 10;
dynamic b = "2.5";
try
{
    Console.WriteLine(a + b);
}
catch (RuntimeBinderException ex)
{
    Console.WriteLine(ex.GetType().Name);
}
Console.WriteLine(a + 2.5);
Console.WriteLine((a + 2.5).GetType().Name);

Dune
Book: Dune Messiah (1965) by Frank Herbert
Frank Herbert
RuntimeBinderException: 'Shelf.Core.Book' does not contain a definition for 'Pages'
Emma 474
102.5
12.5
Double