I'm in high school so I'm a beginner, but I am creating a program to calculate the probabilities of rolling a chosen value given by the user in a textbox, in another textbox, they will need to put the amount of times they want to roll the die, the problem is that it is only outputting 1 number at a time no matter what I do, here is my code so far
Public Class Form1
Private Sub cmdGenerate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdGenerate.Click
' Initialize the random-number generator.
Dim strOutput As String
Dim intCounter As Integer
Dim intArray(txtFirst.Text) As Integer
Dim Random As Integer
For intCounter = 1 To Val(txtFirst.Text)
Randomize()
Random = Int(Rnd() * 6) + 1
intArray(intCounter) = Random
strOutput = intArray(txtFirst.Text)
Next intCounter
txtSequence.Text = strOutput + txtSequence.Text
End Sub
End Class
You overwrite the value of strOutput with each iteration of the loop:
strOutput = intArray(txtFirst.Text)
So by the time you show it to the user, it will have only the last value:
txtSequence.Text = strOutput + txtSequence.Text
Maybe you meant to append to strOutput instead?:
strOutput = strOutput + intArray(txtFirst.Text)
Or perhaps put the last line (which already appends) inside the loop?:
strOutput = intArray(txtFirst.Text)
txtSequence.Text = strOutput + txtSequence.Text
Next intCounter
There are probably a number of different solutions. Consider this a great opportunity to familiarize yourself with stepping through the code in a debugger. There you can observe the runtime values and behavior, line by line, and see specifically where that behavior differs from what you expect.
Since all of your numbers are stored in an array, you don't need strOutput. The join function will concatenate all the items of the array.
txtSequence.Text = String.Join(",", intArray)
Also you don't need to start your variable with str/int.
I believe this will fit your needs:
Textbox.Text = CStr(intArray.Length)
Related
I would like to make a simple program that does the following
Takes a text input of a string and the number of times it needs to be looped by the program user and produces that loop to output that string the number of times stated. My loop isn't doing that. (New to visual basic loops)
Kindly correct advise where i have gone wrong below:
Public Class Form1
Private Sub cmdLoop_Click(sender As Object, e As EventArgs) Handles cmdLoop.Click
Dim newput As String
Dim numberr As Integer
Dim counter As Integer
newput = txtStatement.Text
numberr = TxtRepeatNum.Text
For counter = 1 To numberr
lbloutput.Text = newput & vbCrLf
Next
End Sub
Your loop is writing numberr times the same string into the text box, with every iteration it overwrites the previous content. Change it to
lbloutput.Text = ""
For counter = 1 To numberr
lbloutput.Text = lbloutput.Text & newput & vbCrLf
Next
enter image description hereWrite a program to display 1000 8-character random user IDs in a text box after you click a button. Make sure the program verifies that none of the IDs are identical. Each userid should include a mixture of alphabetic characters and numbers.
What I have so far, which could be enough to get by as a random ID generator alone, but it does not loop 1000 times to be displayed in the label, and doesn't check for repeated ID's.
Public Class Form1
Private Sub btnGenerateRandomID_Click(sender As Object, e As EventArgs) Handles btnGenerateRandomID.Click
Dim rand As New Random
Dim char1 As String
Dim char2 As String
Dim char3 As String
Dim char4 As String
Dim char5 As String
Dim char6 As String
Dim char7 As String
Dim char8 As String
char1 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char2 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char3 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char4 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char5 = rand.Next(0, 9)
char6 = rand.Next(0, 9)
char7 = rand.Next(0, 9)
char8 = rand.Next(0, 9)
lblRandomId.Text = char1 + char2 + char3 + char4 + char5 + char6 + char7 + char8
End Sub
End Class
Thanks.
EDIT:
Public Class Form1
'Write a program to display 1000 8-character random user IDs in a text
'box after you click a button. Make sure the program verifies that none Of the IDs are identical.
'Each userid should include a mixture Of alphabetic characters And numbers.
Private Sub btnGenerateRandomID_Click(sender As Object, e As EventArgs) Handles btnGenerateRandomID.Click
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
Dim rand As New Random
Dim strID As String = ""
For count_ids As Integer = 0 To 999
For count_chars As Integer = 0 To 7
strID += strChar(rand.Next(0, 62))
Next count_chars
lblRandomId.Text = strID
Next
End Sub
End Class
Here is the actual question "Q. Write a program to display 1000 8-character random user IDs in a text box after you click a button. Make sure the program verifies that none of the IDs are identical. Each userid should include a mixture of alphabetic characters and numbers.
Explain your program in your essay, with screenshots. Include a paragraph on the random number generator used in Visual Basic, and answer the question: how should the random number generator be best seeded?"
First of all, Welcome to StackOverflow,
From what i understand from your post you want to generate 1000 8 Character long Unique ID's
First of all we declare our variables
Dim Characters As String = "AZERTYUIOPQSDFGHJKLMWXCVBN0123456789" 'Declare All Characters on one string
Dim IDsList As New List(Of String) With {.Capacity = 1000} 'You can limit the capacity to 1000
Dim Id As String = ""
Dim Rand As New Random
Now we begin to genearte ID's and add them to IDsList using a nested loop
For i As Integer = 0 To 999 'This is a Zero Based Index so 999 is actually 1000
For _i As Integer = 0 To 7 'This also means 7 is 8
Id += Characters(Rand.Next(0, 36))
Next
IDsList.Add(Id)
Id = ""
Next
'You can Check for duplicates by adding this piece of code or use the next one instead
Dim NoDupesIDsList As New List(Of String)
NoDupesIDsList = IDsList.Distinct.ToList
For i As Integer = 0 To 999 'This is a Zero Based Index so 999 is actually 1000
For _i As Integer = 0 To 7 'This also means 7 is 8
Id += Characters(Rand.Next(0, 36))
Next
If not IDsList.contains(Id) then
IDsList.Add(Id)
End if
Id = ""
Next
Use a Textbox with multiline and scroll bar for better experience
Feel free to ask me anything via comments
PS: I tested my method and it's working , enjoy it !
This function will return the ASCII characters between 48 an 122. That will include some characters that are not letters or numbers but this makes the ids even more unique and simplifies the code.
The For loop builds the ids with a length of 8. Then the id is checked for uniqueness with the .Contains method. Only if it is not in the list, it is added to the list and the counter is incremented.
Private Rnd As New Random
Private Function GetListOfIDs() As List(Of String)
Dim Counter As Integer
Dim lst As New List(Of String)
Dim id As String = ""
Do While Counter < 1000
id = ""
For i = 0 To 7
id &= Chr(Rnd.Next(48, 123))
Next
If Not lst.Contains(id) Then
lst.Add(id)
Counter += 1
End If
Loop
Return lst
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim lst = GetListOfIDs()
TextBox1.Text = String.Join(vbCrLf, lst)
End Sub
EDIT
As per suggestion by Caius Jard in comments I have added a solution using a HashSet. Same idea only a HashSet will not accept duplicate entries. The .Add method returns a boolean telling you if the Add was successful.
Private Function GetListOfIDs() As HashSet(Of String)
Dim hs As New HashSet(Of String)
Dim id As String = ""
Do While hs.Count < 1001
id = ""
For i = 0 To 7
id &= Chr(Rnd.Next(48, 123))
Next
If hs.Add(id) Then
Counter += 1
End If
Loop
Return hs
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim hs = BuildHashSet()
TextBox1.Text = String.Join(vbCrLf, hs)
End Sub
This method is probably more efficient because a HashSet is designed for hight performance. For 1000 items I did not notice any difference in the user interface. The text box updated immediately with both methods.
This will create the names:
Function RandomName(length As Integer) As String
Shared rnd As New Random()
Shared corpus() As Char = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".ToCharArray()
Return New String(Enumerable.Range(0, length).Select(Function(c) corpus(rnd.Next(corpus.Length))).ToArray())
End Function
Iterator Function GetUniqueNames(length As Integer, count As Integer) As IEnumerable(Of String)
Dim names As New HashSet(Of String)
For i As Integer = 0 To count
Dim name As String = RandomName(length)
While names.Contains(name)
'Potential (but unlikely) halting problem
name = RandomName(length)
End While
names.Add(name)
Yield name
Next
End Function
Dim uniqueNames = GetUniqueNames(8, 1000)
But do you really want to display 1000 of them in a single label?
lblRandomId.Text = string.Join(vbCrLf, uniqueNames)
Let's talk about your code.
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
This assignment will work in your loop because a String is really an array of Char. This is why you can refer to an index in the string.
Dim rand As New Random()
The .net Random class provides a seed for Random based on system time. Only rarely would you want to provide a seed.
From the docs https://learn.microsoft.com/en-us/dotnet/api/system.random?view=netcore-3.1
CONSTRUCTORS
Random() Initializes a new instance of the Random class
using a default seed value.
Random(Int32) Initializes a new instance of the Random class, using
the specified seed value.
For count_ids As Integer = 0 To 999
A For loop is not appropriate for this problem. We only want to increment the counter if we get a unique ID. The above For loop will increment on every iteration.
Do While Counter < 1000
'Code here
Loop
Notice in my code the counter is only incremented if the ID is unique.
The following loop should work fine but above this code we need to reset strID to an empty string. Otherwise we will have a very long string.
For count_chars As Integer = 0 To 7
strID += strChar(rand.Next(0, 62))
Next count_chars
You should not update the user interface (the label) on each iteration of the loop. Repainting the screen is one of the slowest operations in code. This line will overwrite the string in the label on every iteration.
lblRandomId.Text = strID
Move the update of the UI to after both loops are complete
Your code never checks for duplicates.
Now let's fix it.
We use a List(Of T) to accumulate the IDs. The T stands for Type; in our case it is String. A List is like an array only you don't have to know ahead of time how many entries there will be. No ReDim Preserve required.
Moved Dim strID As String = "" to the beginning of the inner loop so we will get a new strID on each iteration of the outer loop.
Changed strID &= strChar(rand.Next(0, 62)). &= instead of +=. In VB.net we use the ampersand to concatenate strings although the plus sign will work. The .Next method of the Random class has an overload that takes 2 Integers. It is inclusive of the first and exclusive of the second which means (0, 62) will return numbers form 0 to 61. Your string with a length of 62 has indexes of 0 to 61.
Next we check for duplicates with the .Contains method of the List class. This method does just what you would expect. We pass the new ID to the method and it returns a Boolean telling if the string is already in the list.
If it is not in the list, we add it to the list and increment the counter. The counter is only incremented if we have a successful add.
Finally we update the user interface by using a method of the String class. the .Join method takes a separator and the list to join. The TextBox must be multiline and have scroll bars.
I changed the names of the controls so I could test it in my testing program.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim lst As New List(Of String)
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
Dim rand As New Random()
Dim counter As Integer
Do While counter < 1000
Dim strID As String = ""
For count_chars = 0 To 7
strID &= strChar(rand.Next(0, 62))
Next
If Not lst.Contains(strID) Then
lst.Add(strID)
counter += 1
End If
Loop
TextBox1.Text = String.Join(vbCrLf, lst)
End Sub
EDIT
The official documentation for this method can be found here.
https://learn.microsoft.com/en-us/dotnet/api/system.string.join?view=netcore-3.1
I know it will be difficult to read but just take a look. Eventually you will be able to understand it and will be using these docs a lot.
String.Join(separator, List(Of String))
The separator is what to put between the strings in the list. In our case that is vbCrLf which is a vb constant for new line. Cr = Carraiage Return and Lf = Line Feed. Other types of collections that contain strings can also use this method.
The method takes each string in the list and adds the separator. After it is done with the list it returns one long string which we display in the TextBox.
in my programming class I have to create a program which allows the user in order to enter a sentence, with the buttons "Encode" and "Decode" as options. So, for "Encode", you have to translate the sentence into Asc numbers (already did this). However, I'm currently stuck on the "Decode" section, for you have to use a For loop and an array to separate the Asc numbers by spaces, then translate them into characters one by one. Here's what I have so far:
Public Class Form1
Dim Message As String
Dim NewMessage As String
Dim Part As String
Dim Part2 As Integer
Dim Letter As String
Dim Length As String
Dim ints() As Integer
Dim intlength As Integer
Private Sub btn_Enter_Click(sender As Object, e As EventArgs) Handles btn_Enter.Click
Message = txt_Message.Text
Length = Message.Length() - 1
If rbn_Encode.Checked = True Then
For Num As Integer = 0 To Length
Letter = Message(Num)
Me.lbl_Code.Text = lbl_Code.Text & Asc(Letter) & " "
Next
End If
If rbn_Decode.Checked = True Then
For Num As Integer = 0 To intlength Step 1
If Message(Num) <> " " Then
Part = Part & Message(Num)
Else
NewMessage = NewMessage & ChrW(Part) & " "
End If
Next
Me.lbl_Code.Text = NewMessage
End If
End Sub
Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ExitToolStripMenuItem.Click
Application.Exit()
End Sub
End Class
I've been stuck on this for about 2 week, and I'm still clueless. Thank you for your help and have a wonderful day.
This might seem to veer off the topic of the question, but it all meanders towards a better answer.
OK there are a few issues with your code. Firstly, make sure that "Option Strict" is on - have a look here. This will force you to convert types properly and reduce the potential for problems. Bearing the above in mind,
Dim Length As String
should be
Dim Length As Integer
on to the next bit
Each procedure should have a single responsibility. Your btn_Enter.Click event handler includes code for encoding text and decoding numbers. These should be separated out into their own procedures. In a relatively short bit of code like yours, it's not too much of a problem, but even here, it makes things a little fuzzier. Have a look at the code below. There are more issues, but we'll look at them in a moment. The code below is a bit clearer and more maintainable.
Private Sub btn_Enter_Click(sender As Object, e As EventArgs) Handles btn_Enter.Click
Message = txt_Message.Text
Length = Message.Length() - 1
If rbn_Encode.Checked = True Then
EncodeTextToAscii()
End If
If rbn_Decode.Checked = True Then
DecodeToText()
End If
End Sub
Private Sub DecodeToText()
For Num As Integer = 0 To intlength Step 1
If Message(Num) <> " " Then
Part = Part & Message(Num)
Else
NewMessage = NewMessage & ChrW(Part) & " "
End If
Next
Me.lbl_Code.Text = NewMessage
End Sub
Private Sub EncodeTextToAscii()
For Num As Integer = 0 To Length
Letter = Message(Num)
Me.lbl_Code.Text = lbl_Code.Text & Asc(Letter) & " "
Next
End Sub
Next.
In your code to encode the string as ASCII, you store the resulting data directly in the label lbl_Code's text property. The user interface should never be used as the primary store for data. It's bad practice and potentially allows the user to change data accidentally - in textboxes for example. In the case of a label, it's not to important, but it's far better to get into the good habits.
To store your encoded ASCII numbers, you can use the array ints, but as your code stands, the declaration of ints is just that. There is no space in the array to store data. So, in the Encode procedure, you need to resize ints to the same as the number of characters in the string.
So now we have ..
Private Sub EncodeTextToAscii()
ReDim ints(Length)
For Num As Integer = 0 To Length
Letter = Message(Num)
ints(Num) = Asc(Letter)
Next
End Sub
Finally onto the meat of your question. The Decode procedure can now be written as this ..
Private Sub DecodeToText()
NewMessage = ""
For Each asciiNumber As Integer In ints
NewMessage = NewMessage & ChrW(asciiNumber) & " "
Next
Me.lbl_Code.Text = NewMessage
End Sub
Instead of mucking around getting the length of a loop and getting the ascii number in each element of an array, you can simplyfy it using a For Each statement. You dont need to know the length of the array. It just loops over the whole length. Much easier.
As an excercise, try applying the For Each idea to the Encode procedure. :-)
I am currently working on a homework assignment for Visual basic. The homework is to display the square value of only the odd numbers 1-9. I have to use a For Next to do so as specified by the assignment. I do not want the answer but a point to the right direction. Here is my code currently it only displays the square value of 9 but will not display the square value of the other odd numbers. I have done a couple tutorials but I can not figure out why it ill not continue the loop.
Public Class MainForm
Private Sub exitButton_Click(sender As Object, e As EventArgs) Handles exitButton.Click
Me.Close()
End Sub
Private Sub displayButton_Click(sender As Object, e As EventArgs) Handles displayButton.Click
'Start/end values and retainer for the values
Dim startVal As Integer
Dim endVal As Integer
Dim squareVal As Integer
startVal = 1
endVal = 9
'For loop to separate the odd and even numbers to square the odd numbers.
For _val As Integer = startVal To endVal Step 1
If _val Mod 2 <> 0 Then
squareVal = _val * _val
squaresLabel.Text = squareVal.ToString() & ControlChars.NewLine
_val += 1
Else
squaresLabel.Text = _val.ToString() & ControlChars.NewLine
_val += 1
End If
Next _val
End Sub
End Class
You are overwriting the text stored in squaresLabel each pass through the loop. Look at the assignment statement:
squaresLabel.Text = squareVal.ToString() & ControlChars.NewLine
I think you are just repeating the calculation not actually output each value. So I suggest you define an array and store them inside of it. Also do trouble shooting for each value. Hope it helps.
Recently when creating a program for my client as part of my computing project in visual basic .net I've came across a problem, which looks like following; In order to receive additional marks for my program I must take an advantage of either Binary Search or Insertion Sort subroutine declared recursively, so far the only place I can use it on is my View form which displays all reports generated by program but the problem with this is since I'm using MS Access to store my data all of the data is downloaded and placed in listview in load part of form. So the only way I can use it is by running it on listview which is a major problem for me due to the fact that I'm not very experienced in vb.
For binary search I have tried downloading all of the items in specified by user column into an array but that's the bit I was struggling on the most because I'm unable to download all items from only one column into an array. Also instead of searching every single column user specifies in my form in which column item is located (For example "19/02/2013" In Column "Date"), In my opinion if I manage to download every single entry in specified column into an array it should allow me to run binary search later on therefore completing the algorithm. Here's what I've got so far.
Sub BinarySearch(ByVal Key As String, ByVal lowindex As String, ByVal highindex As String, ByVal temp() As String)
Dim midpoint As Integer
If lowindex > highindex Then
MsgBox("Search Failed")
Else
midpoint = (highindex + lowindex) / 2
If temp(midpoint) = Key Then
MsgBox("found at location " & midpoint)
ElseIf Key < temp(midpoint) Then
Call BinarySearch(Key, lowindex, midpoint, temp)
ElseIf Key > temp(midpoint) Then
Call BinarySearch(Key, midpoint, highindex, temp)
End If
End If
End Sub
Private Sub btnSearch_Click(sender As System.Object, e As System.EventArgs) Handles btnSearch.Click
Dim Key As String = txtSearch.Text
Dim TargetColumn As String = Me.lstOutput.Columns(cmbColumns.Text).Index
Dim lowindex As Integer = 0
Dim highindex As Integer = lstOutput.Items.Count - 1
'Somehow all of the items in Target column must be placed in temp array
Dim temp(Me.lstOutput.Items.Count - 1) As String
' BinarySearch(Key, lowindex, highindex, temp)
End Sub
For Insertion sort i don't even have a clue how to start, and the thing is that I have to use my own subroutine instead of calling system libraries which will do it for me.
Code which I have to use looks like following:
Private Sub InsertionSort()
Dim First As Integer = 1
Dim Last As Integer = Me.lstOutput.
Dim CurrentPtr, CurrentValue, Ptr As Integer
For CurrentPtr = First + 1 To Last
CurrentValue = A(CurrentPtr)
Ptr = CurrentPtr - 1
While A(Ptr) > CurrentValue And Ptr > 0
A(Ptr + 1) = A(Ptr)
Ptr -= 1
End While
A(Ptr + 1) = CurrentValue
Next
Timer1.Enabled = False
lblTime.Text = tick.ToString
End Sub
Any ideas on how to implement this code will be very appreciated, and please keep in my mind that I'm not very experienced in this language
Perhaps this might give you a place to begin. If you already have a ListView with "stuff" in it you could add a button to the form with the following code to copy the Text property for each item into an array:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myArray(Me.ListView1.Items.Count - 1) As String
Dim i As Integer
' load array
For i = 0 To Me.ListView1.Items.Count - 1
myArray(i) = Me.ListView1.Items(i).Text
Next
' show the results
Dim s As String = ""
For i = 0 To UBound(myArray)
s &= String.Format("myArray({0}): {1}", i, myArray(i)) & vbCrLf
Next
MsgBox(s, MsgBoxStyle.Information, "myArray Contents")
' now go ahead and manipulate the array as needed
' ...
End Sub