Some examples include such work arounds related to "How can we use VB to build WebAssembly applications?" or "How can we use VB to build Xamarin applications?"
Emulation of C#-style "ref local". See https://docs.microsoft.com/en-us/dotnet/csharp/write-safe-efficient-code for background.
' Start off with a Console application project.
' Be sure these options are On:
' Option Strict On
' Option Infer On
' Imports:
' Imports System.Runtime.InteropServices
Structure Xyz
Dim x As Short
Dim y As Integer
Dim z As Long
Dim u As Single
Dim v As Double
End Structure
Sub Main()
Dim pdq0 As Xyz
Dim pdq1 As Xyz
Dim pdq2 As Xyz
' Inferencing is the only way to have a properly typed
' variable of Span(Of Xyz).
Dim refOf_Xyz = MemoryMarshal.CreateSpan(Of Xyz)(Nothing, 0)
' refOf_Xyz(0) is almost works like a Dim ByRef x As Xyz;
' a ref local, if you will.
' Alternative to refOf_Xyz(0) is MemoryMarshal.GetReference(refOf_Xyz).
' WARNING! VB can only be a consumer of ref types, and then
' only by way of a ByRef parameter to function or lambda!
' Also, avoid directly using such in a With statement!
' Reference to pdq0
refOf_Xyz = MemoryMarshal.CreateSpan(pdq0, 1)
Call (Sub(ByRef x As Xyz) x.x = 1)(refOf_Xyz(0))
' Reference to pdq1
refOf_Xyz = MemoryMarshal.CreateSpan(pdq1, 1)
Call Sub(ByRef x As Xyz)
With x
.x = 2
.y = 3
.z = 4
.u = 1.234
.v = 987654321.12345684
End With
End Sub(MemoryMarshal.GetReference(refOf_Xyz))
' Reference to pdq2
refOf_Xyz = MemoryMarshal.CreateSpan(pdq2, 1)
Call Sub(ByRef x As Xyz)
x.u = 2.468
x.v = 111222333444.55566
End Sub(refOf_Xyz(0))
' Now examine pdq0, pdq1, and pdq2
' Confirm they have had their fields asssigned as expected.
Stop
End Sub
Folks have long desired for a way to use
For Each upon a collection of Structure (a.k.a. value) types that allows for mutations (state changes) of such. Here is one straight-forward approach, which can be used on any object which implements IList(Of T) - a demonstration of the ByIndex extensions.' Start off with a Console application project.
' Be sure these options are On:
' Option Strict On
' Option Infer On
' Imports:
' Imports System.Runtime.CompilerServices
Structure Xyz
Dim x As Short
Dim y As Integer
Dim z As Long
Dim u As Single
Dim v As Double
End Structure
Sub Main()
Dim arrayOf_Xyz(9) As Xyz
For Each item In arrayOf_Xyz.ByIndex
' item.List would be the IList(Of Xyz)
' item.Index is the index into the above IList
' item.Value is a property to item.List(item.Index);
' however, it is still stuck as a pass by value
' situation. Hence the use of a lambda, like so:
Dim itemIndex = item.Index
item.Call(Sub(ByRef x)
' This is the only reliable way, in pure VB,
' short of somehow using Span(Of T), to get at
' a reference to a Structure rather than its copy.
x.x = CShort(itemIndex And 3)
x.y = itemIndex And 7
x.z = (x.x * x.y) Xor itemIndex
x.u = CSng(itemIndex / 100)
x.v = itemIndex / 10
End Sub)
Next
' Now examine elements in arrayOf_Xyz
' Confirm they have had their fields asssigned as expected.
Stop
For Each item In arrayOf_Xyz.ByIndex(2, 3)
' ByIndex can do ranges; here we start with arrayOf_Xyz(2)
' and loop through arrayOf_Xyz(2 + 3 - 1), i.e. arrayOf_Xyz(4).
item.Call(Sub(ByRef x)
x.z *= 2
x.u *= 5
End Sub)
Next
' Now examine elements in arrayOf_Xyz
' Confirm only indicies 2 through 4 have had their
' fields asssigned as expected.
Stop
' Note that item.Call can also take AddressOf some
' applicable function.
For Each item In arrayOf_Xyz.ByIndex(7)
item.Call(AddressOf Foo)
Next
' Now examine elements in arrayOf_Xyz
' Confirm only indicies 7 through 9 have had their
' fields asssigned as expected.
Stop
End Sub
Sub Foo(ByRef x As Xyz)
x.v = 1 + Math.Sqrt(Math.Abs(x.v))
End SubRegion "For Each ByIndex Extensions"
Delegate Sub ByIndexAction(Of T)(ByRef Item As T)
Structure ByIndexItem(Of T)
Public ReadOnly List As IList(Of T)
Public ReadOnly Index As Integer
Public Sub New(List As IList(Of T), Index As Integer)
Me.List = List
Me.Index = Index
End Sub
Sub [Call](Action As ByIndexAction(Of T))
Action(List(Index))
End Sub
Public Property Value As T
Get
Return List(Index)
End Get
Set(value As T)
List(Index) = value
End Set
End Property
End Structure
<Extension> Iterator Function ByIndex(Of T)(List As IList(Of T)) _
As IEnumerable(Of ByIndexItem(Of T))
For i As Integer = 0 To List.Count - 1
Yield New ByIndexItem(Of T)(List, i)
Next
End Function
<Extension> Iterator Function ByIndex(Of T)(List As IList(Of T), Start As Integer) _
As IEnumerable(Of ByIndexItem(Of T))
If Start < 0 OrElse Start >= List.Count Then Exit Function
For i As Integer = Start To List.Count - 1
Yield New ByIndexItem(Of T)(List, i)
Next
End Function
<Extension> Iterator Function ByIndex(Of T)(List As IList(Of T),
Start As Integer, Length As Integer) _
As IEnumerable(Of ByIndexItem(Of T))
If Start < 0 OrElse Start >= List.Count Then Exit Function
If Length <= 0 OrElse (Start + Length) > List.Count Then Exit Function
For i As Integer = 0 To Length - 1
Yield New ByIndexItem(Of T)(List, Start + i)
Next
End FunctionEnd Region
This is a somewhat shady, but likely safe enough, approach to process through an array (note, must be an array!) of
Structure (a.k.a. value) types. Utilizing the Enumerator of Span(Of T), this is a handy way to access the array elements in a memory efficient manner, and allows for mutations (state changes). The hitch is one must work through a Delegate (such as a lambda or AddressOf function).' Start off with a Console application project.
' Be sure these options are On:
' Option Strict On
' Option Infer On
' Imports:
' Imports System.Runtime.CompilerServices
' Imports System.Runtime.InteropServices
Structure Xyz
Dim x As Short
Dim y As Integer
Dim z As Long
Dim u As Single
Dim v As Double
End Structure
Sub Main()
Dim arrayOf_Xyz(9) As Xyz
Dim itemOrdinal = -1
arrayOf_Xyz.ForEachByRef(
Sub(ByRef x)
' ByRef parameter of lambda or function:
' This is the only way in VB to dereference a Span(Of Xyz),
' and get at a reference to a Structure rather than its copy.
itemOrdinal += 1
x.x = CShort(itemOrdinal And 3)
x.y = itemOrdinal And 7
x.z = (x.x * x.y) Xor itemOrdinal
x.u = CSng(itemOrdinal / 100)
x.v = itemOrdinal / 10
End Sub)
' Now examine elements in arrayOf_Xyz
' Confirm they have had their fields asssigned as expected.
Stop
arrayOf_Xyz.ForEachByRef(2, 3,
Sub(ByRef x)
' ForEachByRef can do slices; here we start with arrayOf_Xyz(2)
' and loop through arrayOf_Xyz(2 + 3 - 1), i.e. arrayOf_Xyz(4).
x.z *= 2
x.u *= 5
End Sub)
' Now examine elements in arrayOf_Xyz
' Confirm only indicies 2 through 4 have had their
' fields asssigned as expected.
Stop
arrayOf_Xyz.ForEachByRef(2, 3,
Sub(ByRef x)
' ForEachByRef can do slices; here we start with arrayOf_Xyz(2)
' and loop through arrayOf_Xyz(2 + 3 - 1), i.e. arrayOf_Xyz(4).
x.z *= 2
x.u *= 5
End Sub)
' Now examine elements in arrayOf_Xyz
' Confirm only indicies 2 through 4 have had their
' fields asssigned as expected.
Stop
' Note that ForEachByRef can also take AddressOf some
' applicable function.
arrayOf_Xyz.ForEachByRef(7, AddressOf Foo)
' Now examine elements in arrayOf_Xyz
' Confirm only indicies 7 through 9 have had their
' fields asssigned as expected.
Stop
End Sub
Sub Foo(ByRef x As Xyz)
x.v = 1 + Math.Sqrt(Math.Abs(x.v))
End SubRegion "ForEachByRef Extensions"
Delegate Sub ForEachAction(Of T As Structure)(ByRef Item As T)
<Extension> Sub ForEachByRef(Of T As Structure)(
Array As T(),
Action As ForEachAction(Of T))
With Array.AsSpan().GetEnumerator()
Do While .MoveNext()
Action(.Current)
Loop
End With
End Sub
<Extension> Sub ForEachByRef(Of T As Structure)(
Array As T(),
Start As Integer,
Action As ForEachAction(Of T))
With Array.AsSpan().Slice(Start).GetEnumerator()
Do While .MoveNext()
Action(.Current)
Loop
End With
End Sub
<Extension> Sub ForEachByRef(Of T As Structure)(
Array As T(),
Start As Integer,
Length As Integer,
Action As ForEachAction(Of T))
With Array.AsSpan().Slice(Start, Length).GetEnumerator()
Do While .MoveNext()
Action(.Current)
Loop
End With
End Sub
<Extension> Sub ForEachByRef(Of T As Structure)(
List As IList(Of T),
Action As ForEachAction(Of T))
Dim itemSize As Integer = Marshal.SizeOf(Of T)()
For index As Integer = 0 To List.Count - 1
Dim itemSpan = MemoryMarshal.CreateSpan(List(index), itemSize)
Action(itemSpan(0))
Next
End Sub
<Extension> Sub ForEachByRef(Of T As Structure)(
List As IList(Of T),
Start As Integer,
Action As ForEachAction(Of T))
If Start < 0 Then Exit Sub
Dim itemSize As Integer = Marshal.SizeOf(Of T)()
For index As Integer = Start To List.Count - 1
Dim itemSpan = MemoryMarshal.CreateSpan(List(index), itemSize)
Action(itemSpan(0))
Next
End Sub
<Extension> Sub ForEachByRef(Of T As Structure)(
List As IList(Of T),
Start As Integer,
Length As Integer,
Action As ForEachAction(Of T))
If Start < 0 Then Exit Sub
If Length <= 0 Then Exit Sub
Dim itemSize As Integer = Marshal.SizeOf(Of T)()
For index As Integer = Start To Start + Length - 1
Dim itemSpan = MemoryMarshal.CreateSpan(List(index), itemSize)
Action(itemSpan(0))
Next
End SubEnd Region
Is there a way to split the code (non Shared) in a Form into 2 files. My main form Form1 is huge and very difficult to work with. I have Regions for each group of functionality but I would like to move these to into 1 or more files. If I create another file and set it to "Partial Public Class Form1" it gets created as a new Form with its own designer and Resx file but can access all the things it needs from Form1, if you select open designer it opens it own designer . The original form does not need to access anything in the new form. The new form just has events handlers and private functions. If that is impossible what about just the private functions in a helper file. The private functions access items on Form1.
@paul1956 I believe you are running into what I would consider a "bug" in the IDE. If you were to do this outside of VS, I believe it would work as you were thinking... but in VS, it tries to "do more" and that "more" is wrong. Incidentially, I do exactly what you are doing all the time... especially when I'd like to keep everyting Option Strict On (in the main form file) but have a partial form file that contains the Option Strict Off functionality. I do it this way so that it is still internal to the form... not some module or class where it could potentially be seen (or rather used).
Meaning, if you don't double-click on it... only use the "view code" functionality... it should work like you are expecting - and just be OK with the fact that the occasional double-click will occur where you see a "blank form"... immediately close out of that (not saving it) and be "OK" with it. ;-)
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