List(of String) or Array or ArrayList - vb.net

Hopefully a simple question to most programmers with some experience.
What is the datatype that lets me do this?
Dim lstOfStrings as *IDK*
Dim String0 As String = "some value"
Dim String1 As String = "some value"
Dim String2 As String = "some value"
Dim String3 As String = "some value"
Dim String4 As String = "some value"
Dim String5 As String = "some value"
lstOfStrings.add(String0, String1, String2, String3)
I would access these like this
Dim s1 = lstOfStrings(0)
Dim s2 = lstOfStrings(1)
Dim s3 = lstOfStrings(2)
Dim s4 = lstOfStrings(3)
if I use List(of String)
I am only able to .add one thing to the list (at a time), and in my function I want to be able to store several values(at a time).
Solution:
Private Function Foo() As List(Of String)
Dim temp1 As String
Dim temp2 As String
Dim temp3 As String
Dim temp4 As String
Dim temp5 As String
Dim temp6 As String
Dim inputs() As String = {temp1, temp2, temp3, temp4, temp5, temp6}
Dim lstWriteBits As List(Of String) = New List(Of String)(inputs)
Return lstWriteBits
End Function

List(Of String) will handle that, mostly - though you need to either use AddRange to add a collection of items, or Add to add one at a time:
lstOfString.Add(String1)
lstOfString.Add(String2)
lstOfString.Add(String3)
lstOfString.Add(String4)
If you're adding known values, as you show, a good option is to use something like:
Dim inputs() As String = { "some value", _
"some value2", _
"some value3", _
"some value4" }
Dim lstOfString as List(Of String) = new List(Of String)(inputs)
' ...
Dim s3 = lstOfStrings(3)
This will still allow you to add items later as desired, but also get your initial values in quickly.
Edit:
In your code, you need to fix the declaration. Change:
Dim lstWriteBits() As List(Of String)
To:
Dim lstWriteBits As List(Of String)
Currently, you're declaring an Array of List(Of String) objects.

You can do something like this,
Dim lstOfStrings As New List(Of String) From {"Value1", "Value2", "Value3"}
Collection Initializers

Neither collection will let you add items that way.
You can make an extension to make for examle List(Of String) have an Add method that can do that:
Imports System.Runtime.CompilerServices
Module StringExtensions
<Extension()>
Public Sub Add(ByVal list As List(Of String), ParamArray values As String())
For Each s As String In values
list.Add(s)
Next
End Sub
End Module
Now you can add multiple value in one call:
Dim lstOfStrings as New List(Of String)
lstOfStrings.Add(String1, String2, String3, String4)

look to the List AddRange method here

Sometimes I don't want to add items to a list when I instantiate it.
Instantiate a blank list
Dim blankList As List(Of String) = New List(Of String)
Add to the list
blankList.Add("Dis be part of me list") 'blankList is no longer blank, but you get the drift
Loop through the list
For Each item in blankList
' write code here, for example:
Console.WriteLine(item)
Next

You can use IList(Of String) in the function :
Private Function getWriteBits() As IList(Of String)
Dim temp1 As String
Dim temp2 As Boolean
Dim temp3 As Boolean
'Pallet Destination Unique
Dim temp4 As Boolean
Dim temp5 As Boolean
Dim temp6 As Boolean
Dim lstWriteBits As Ilist = {temp1, temp2, temp3, temp4, temp5, temp6}
Return lstWriteBits
End Function
use
list1.AddRange(list2) to add lists
Hope it helps.

For those who are stuck maintaining old .net, here is one that works in .net framework 2.x:
Dim lstOfStrings As New List(of String)( new String(){"v1","v2","v3"} )

Related

Convert a List to a Dictionary with a unique numbered key

How can this code be accomplished using ToDictionary() instead of a For Each
Dim stringDict As Dictionary(Of String, String) = new Dictionary(Of Integer, String)
Dim stringList As List(Of String) = {"alpha", "beta", "gamma", "delta"}
For Each stringItem As String In stringList
stringDict.Add($"Entry{stringDict.Count+1}",stringItem)
Next
This is what I am trying to do:
Dim stringDict As Dictionary(Of String, String) = stringList.ToDictionary(Function(a) $"Entry{?}", Function(b) b)
I was hoping there might be a variable with the current row or index, or an incrementor
You can use the overload of Select that gives you the index:
Dim stringDict As Dictionary(Of String, String) = stringList.
Select(Function(s, index) (Key:=$"Entry{index + 1}", Value:=s)).
ToDictionary(Function(kv) kv.Key, Function(kv) kv.Value)
However, i find your loop more readable. You should also set Option Strict to On, following should give you a compiler error:
Dim stringDict As Dictionary(Of String, String) = new Dictionary(Of Integer, String)
You can use Enumerable.Range (documentation) to create a range of numbers from 1 to the Count of your List and then Enumerable.ToDictionary (documentation) to convert that range to a Dictionary.
Example:
Dim stringList As New List(Of String) From {"alpha", "beta", "gamma", "delta"}
Dim stringDict = Enumerable.Range(1, stringList.Count).ToDictionary(Function(i) $"Entry{i}", Function(i) stringList.Item(i - 1))
Fiddle: https://dotnetfiddle.net/4xHp9g

ContainsValue with Dictionary(Of String, Items)

How to know if a dictionary with multiple values contains specific value?
'Create dictionary
Dim testDictionary As New Dictionary(Of String, Items)
'Code to fill dictionary
'.......................
'.......................
'.......................
'Test if a specific value is contained in dictionary
Dim testValue as String = "TEST"
testDictionary.ContainsValue(testValue) 'This doesn't work
Public Class Items
Public Property Property1 As String
Public Property Property2 As String
Public Sub New()
End Sub
End Class
If you can define how to determine whether the dictionary contains that string, pass that logic into Enumerable.Any
Dim testValue As String = "TEST"
Dim contains = testDictionary.Any(Function(kvp) kvp.Value.Property1 = testValue OrElse kvp.Value.Property2 = testValue)
If contains Then
Dim containsEntries = testDictionary.Where(Function(kvp) kvp.Value.Property1 = testValue OrElse kvp.Value.Property2 = testValue)
End If
Since you reuse it for Any and Where, you can declare the predicate once
Dim predicate =
Function(kvp As KeyValuePair(Of String, Items))
Return kvp.Value.Property1 = testValue OrElse kvp.Value.Property2 = testValue
End Function
Dim contains = testDictionary.Any(predicate)
If contains Then
Dim containsEntries = testDictionary.Where(predicate)
End If
This is hard-coded to just these properties Property1 and Property2.
(you really don't need the Any if you want the entities; I just figured the Any answered your question "How to know if..." with a boolean)
If you want to check all public instance string properties, you can use reflection
Dim predicate =
Function(kvp As KeyValuePair(Of String, Items))
Return GetType(Items).
GetProperties(Reflection.BindingFlags.Public Or Reflection.BindingFlags.Instance).
Where(Function(pi) pi.PropertyType Is GetType(String)).
Aggregate(False, Function(pi1, pi2) pi1 Or (pi2.GetValue(kvp.Value) = testValue))
End Function
Dim containsWith = testDictionary.Any(predicate)
If containsWith Then
Dim containsEntries = testDictionary.Where(predicate)
End If

Searching Multiple strings with 1st criteria, then searching those returned values with a different criteria and so on

so..
I have a txt file with hundreds of sentences or strings.
I also have 4 comboboxes with options that a user can select from and
each combobox is part of a different selection criteria. They may or may not use all the comboboxes.
When a user selects an option from any combobox I use a For..Next statement to run through the txt file and pick out all the strings that contain or match whatever the user selected. It then displays those strings for the user to see, so that if they wanted to they could further narrow down the search from that point by using the 3 remaining comboboxes making it easier to find what they want.
I can achieve this by using lots of IF statements within the for loop but is that the only way?
No, there are other ways. You can leverage LINQ to get rid of some of those if statements:
Private _lstLinesInFile As List(Of String) = New List(Of String)
Private Function AddClause(ByVal qryTarget As IEnumerable(Of String), ByVal strToken As String) As IEnumerable(Of String)
If Not String.IsNullOrWhiteSpace(strToken) Then
qryTarget = qryTarget.Where(Function(ByVal strLine As String) strLine.Contains(strToken))
End If
Return qryTarget
End Function
Public Sub YourEventHandler()
'Start Mock
Dim strComboBox1Value As String = "Test"
Dim strComboBox2Value As String = "Stack"
Dim strComboBox3Value As String = String.Empty
Dim strComboBox4Value As String = Nothing
'End Mock
If _lstLinesInFile.Count = 0 Then
'Only load from the file once.
_lstLinesInFile = IO.File.ReadAllLines("C:\Temp\Test.txt").ToList()
End If
Dim qryTarget As IEnumerable(Of String) = (From strTarget In _lstLinesInFile)
'Assumes you don't have to match tokens that are split by line breaks.
qryTarget = AddClause(qryTarget, strComboBox1Value)
qryTarget = AddClause(qryTarget, strComboBox2Value)
qryTarget = AddClause(qryTarget, strComboBox3Value)
qryTarget = AddClause(qryTarget, strComboBox4Value)
Dim lstResults As List(Of String) = qryTarget.ToList()
End Sub
Keep in mind this is case sensitive so you may want to throw in some .ToLower() calls in there:
qryTarget = qryTarget.Where(Function(ByVal strLine As String) strLine.ToLower().Contains(strToken.ToLower()))
I think a compound If statement is the simplest:
Dim strLines() As String = IO.File.ReadAllText(strFilename).Split(vbCrLf)
Dim strSearchTerm1 As String = "Foo"
Dim strSearchTerm2 As String = "Bar"
Dim strSearchTerm3 As String = "Two"
Dim strSearchTerm4 As String = ""
Dim lstOutput As New List(Of String)
For Each s As String In strLines
If s.Contains(strSearchTerm1) AndAlso
s.Contains(strSearchTerm2) AndAlso
s.Contains(strSearchTerm3) AndAlso
s.Contains(strSearchTerm4) Then
lstOutput.Add(s)
End If
Next

Split() doesn't work properly

well I'm doing a computing assessment and well I've ran into an issue with splitting a string. For some reason when the string splits the array stores the whole thing in Variable(0). The error that occurs is when it tries to assign TicketID(Index) a value, it says that the array is out of bound.
Here's the code:
Private Sub ReadInformation(ByRef TicketID() As String, CustomerID() As String, PurchaseMethod() As Char, NumberOfTickets() As Integer, FileName As String)
Dim Line, TextArray(3) As String
Dim Index As Integer
FileOpen(1, FileName, OpenMode.Input)
For Index = 0 To 499
Input(1, Line)
TextArray = Line.Split(",")
CustomerID(Index) = TextArray(0)
TicketID(Index) = TextArray(1)
NumberOfTickets(Index) = TextArray(2)
PurchaseMethod(Index) = TextArray(3)
MessageBox.Show(CustomerID(Index))
Next
FileClose()
End Sub
Here's the first 10 lines of the TextFile I'm trying to read:
C001,F3,10,S
C002,F3,2,O
C003,F3,3,S
C004,W2,9,S
C005,T3,10,S
C006,F3,2,S
C007,W1,3,O
C008,W3,1,O
C009,T2,2,S
C010,F2,9,O
Here's the Error Message I receive:
Error Message
I would use some Lists instead of arrays. In this way you don't have to worry about length of the arrays or if there are fewer lines than 500. Of course, using the more advanced NET Framework methods of the File.IO namespace is a must
Private Sub ReadInformation(TicketID As List(Of String), _
CustomerID As List(Of String), _
PurchaseMethod As List(Of Char), _
NumberOfTickets As List(Of Integer), _
FileName As String)
for each line in File.ReadLines(FileName)
Dim TextArray = Line.Split(","c)
if TextArray.Length > 3 Then
CustomerID.Add(TextArray(0))
TicketID.Add(TextArray(1))
' This line works just because you have Option Strict Off
' It should be changed as soon as possible
NumberOfTickets.Add(TextArray(2))
PurchaseMethod.Add(TextArray(3))
End If
Next
End Sub
You can call this version of your code declaring the 4 lists
Dim TicketID = New List(Of String)()
Dim CustomerID = New List(Of String)()
Dim PurchaseMethod = New List(Of Char)()
Dim NumberOfTickets = New List(Of Integer)()
ReadInformation(TicketID, CustomerID, PurchaseMethod, NumberOfTickets, FileName)
Another approach more Object Oriented is to create a class that represent a line of your data. Inside the loop you create instances of that class and add the instance to a single List
Public Class CustomerData
Public Property TicketID As String
Public Property CustomerID As String
Public Property NumberOfTickets As Integer
Public Property PurchaseMethod As Char
End Class
Now the loop becomes
Private Function ReadInformation(FileName As String) as List(Of CustomerData)
Dim custData = New List(Of CustomerData)()
For Each line in File.ReadLines(FileName)
Dim TextArray = Line.Split(","c)
if TextArray.Length > 3 Then
Dim data = new CustomerData()
data.CustomerID = TextArray(0)
data.TicketID = TextArray(1)
data.NumberOfTickets = TextArray(2)
data.PurchaseMethod = TextArray(3)
custData.Add(data)
End If
Next
return custData
End Function
This version requires the declaration of just one list
You can call this version of your code passing just the filename and receiving the result fo the function
Dim customers = ReadInformation(FileName)
For Each cust in customers
Console.WriteLine(cust.CustomerID)
...
Next
Or use it as an array
Dim theFirstCustomer = customers[0]
Console.WriteLine(theFirstCustomer.CustomerID)

setting strings_array(0) = "" problem

im getting an exception on this:
Dim strings_extreme As String()
strings_extreme(0) = ""
it says that i am using it before it is being assigned a value
how do i initialize it?
please note that i need to be able to do this:
strings_extreme = input.Split(","c).Distinct().OrderBy(Function(s) s)
If you truly don't know how many strings there are going to be, then why not just use an IList:
Dim stringList As IList(Of String) = New List(Of String)
stringList.Add("")
You can get the Count of how many strings there are and you can For Each through all the strings in the list.
EDIT: If you're just trying to build an array from a Split you should be able to do this:
Dim strings_extreme() As String = input.Split(...)
Dim strings_extreme As List(Of String) = New List(Of String)
strings_extreme.Add("value1")
strings_extreme.Add("value 2")
strings_extreme.Add("value 3rd")
strings_extreme.Add("value again")
Dim strings() As String = strings_extreme.ToArray()
...
Dim strings_extreme(10) As String
strings_extreme(0) = ""
Further info: http://www.startvbdotnet.com/language/arrays.aspx
Dim strings_extreme as String() = {"yourfirstitem"}
But actually, why not take a look at some more advanced data structure from System.Collections namespace?
Shouldn't bother setting a string to "".
Try using:
Dim strings_extreme(10) As String
strings_extreme(yourIndex) = String.Empty