Only show a certain count of textboxes in vb.net - vb.net

Question

I'm trying to make several TextBoxes visible and invisible, depending on the number in another textbox. In Fact I have 14(TextBox1, TextBox2, ...), this is my code so far:
Dim s As Integer = 0
While s > 14
s += 1
Dim txtBox As String = "TextBox" & CStr(s)
CObj(txtBox).Visible = False
End While
If txtBoxHowmany.Text = "" Then
Else
Dim s As Integer = 0
While s > txtBoxHowmany.Text
s += 1
Dim txtBox As String = "TextBox" & CStr(s)
CObj(txtBox).Visible = True
End While
End If

Answer 1

I created a list of text boxes and filled it in form Load. You can use this list in any method in your form.
In the Button.Click I used .TryParse to check the contents of TextBox7. I added a number range to the test with AndAlso's. AndAlso short circuits the If so that the following conditions will not be checked if the previous condition is False.
Next we use the .Take extension Function to get the text boxes we want to alter. A For Each loop actual changes the .Visible state.
Private TBoxes As New List(Of TextBox)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
TBoxes.AddRange({TextBox1, TextBox2, TextBox3, TextBox4, TextBox5, TextBox6})
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim NumVisible As Integer
If Integer.TryParse(TextBox7.Text, NumVisible) AndAlso NumVisible > 0 AndAlso NumVisible < 15 Then
Dim VisibleBoxes = TBoxes.Take(NumVisible)
For Each tb In VisibleBoxes
tb.Visible = True
Next
Else
MessageBox.Show("Please enter a valid number.")
End If
End Sub

Answer 2

Design tip: use a spinner instead of a textbox.
Then you define the Minimum and Maximum values, while Value represents the currently-selected value. That makes the code more robust against incorrect input.
So the code could look like this:
dim s as integer = Me.spinner.Value
For i as Integer = 1 to s
Me.Controls("TextBox" & s.ToString).Visible = True
next
If value 5 is selected, then TextBox1 through TextBox5 become visible and you can continue with the rest and hide them as required.
Or a slightly more advanced example:
dim s as integer = me.spinner.Value
For Each ctl As Control In Me.Controls
Dim i as integer = 1
If TypeOf ctl Is TextBox Then
If ctl.Name.StartsWith("TextBox") Then
If ctl.Name = ("TextBox" & i.ToString()) ' eg TextBox1, TextBox5...
If i <= s Then ' counter <= value of spinner
ctl.Visible= True
Else
ctl.Visible= False
End If
End If
i += 1
End If
End If
Next
Here we loop on the form's child controls, look for those of Textbox type. i is an internal counter that is incremented at each occurrence of a TextBox control which name starts with 'TextBox'. If the control name starts with TextBox, and the rest of the string is a number <= spinner value, we set the Visible property to True. Otherwise, Visible is set to False.
So if the spinner value is 5, controls TextBox1 through TextBox5 should become visible, while the rest are to be hidden. The advantage to this approach is that the number of textboxes can be variable.
Disclaimer: untested code.
Update 09 March 2020
Here is a revised version that relies on a LINQ query to fetch a sorted list of textboxes in the form, assuming your controls are always named in the same pattern ie textbox1 through 14.
In theory this code could do the trick but it will not sort like I want ie textbox1 will be followed by textbox11, 12, 13, 14 and then textbox2.
Dim textboxes= From txt In Me.TableLayoutPanel1.Controls.OfType(Of TextBox)() _
Where txt.Name.StartsWith("TextBox") _
Order By txt.Name ' 1, 2, 14...
So I have tweaked the expression a little bit. I am assigning a variable textbox_number from LINQ to extract the number of the textbox:
Dim textboxes = From txt In Me.TableLayoutPanel1.Controls.OfType(Of TextBox)() _
Let textbox_number = Convert.ToInt32(txt.Name.Substring(7, txt.Name.Length - 7)) _
Where txt.Name.StartsWith("TextBox") _
Order By textbox_number ' 1, 2, 14...
This function is for demonstration purposes and should be improved to be made safer. It will work for your purpose though. By doing this trick I can perform a numeric sort so that that the controls are listed in the right order.
So if you select 5 in the spinner then controls 1 through 5 are made visible and the rest are hidden.
I have attached a screenshot. Note that I put all the textboxes in a TableLayoutPanel to improve presentation.
Probably, your controls are placed directly in the form and not in a container, then simply replace Me.TableLayoutPanel1.Controls with Me.Controls.
Public Class frmtextboxes
Private Sub butShow_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles butShow.Click
Dim s As Integer = Me.spinner.Value ' number of textboxes to show
' LINQ query: get list of textboxes sorted by number
Dim textboxes = From txt In Me.TableLayoutPanel1.Controls.OfType(Of TextBox)() _
Let textbox_number = Convert.ToInt32(txt.Name.Substring(7, txt.Name.Length - 7)) _
Where txt.Name.StartsWith("TextBox") _
Order By textbox_number ' 1, 2, 14...
For Each ctl In textboxes
Console.WriteLine("TextBox found, name: " & ctl.txt.Name & "=> " & ctl.textbox_number)
If ctl.textbox_number <= s Then
Me.TableLayoutPanel1.Controls(ctl.txt.Name).Visible = True ' make control visible
Else
Me.TableLayoutPanel1.Controls(ctl.txt.Name).Visible = False ' hide control
End If
Next
End Sub
End Class