Assign value for each label name - vb.net

Question

Can someone teach me how to assign a value for each label with the same name?.
For example, I have a 10 label with the name label1 until label10. On each label,i want to show different value from sql. This is my code.
Dim sqlCmd As New SqlCommand("select distinct top 15 Machine_no from table5 ", conn)
Dim sqlDa As New SqlDataAdapter(sqlCmd)
sqlDa.Fill(dt)
If dt.Rows.Count > 0 Then
For i As Integer = 0 To dt.Rows.Count
lblMachine1.text = dt.Rows(0)("Machine_no").ToString)
lblMachine2.Text = dt.Rows(1)("Machine_no").ToString
lblMachine3.Text = dt.Rows(2)("Machine_no").ToString
lblMachine4.Text = dt.Rows(3)("Machine_no").ToString
lblMachine5.Text = dt.Rows(4)("Machine_no").ToString
lblMachine6.Text = dt.Rows(5)("Machine_no").ToString
lblMachine7.Text = dt.Rows(6)("Machine_no").ToString
lblMachine8.Text = dt.Rows(7)("Machine_no").ToString
lblMachine9.Text = dt.Rows(8)("Machine_no").ToString
lblMachine10.Text = dt.Rows(9)("Machine_no").ToString
lblMachine11.Text = dt.Rows(10)("Machine_no").ToString
lblMachine12.Text = dt.Rows(11)("Machine_no").ToString
lblMachine13.Text = dt.Rows(12)("Machine_no").ToString
lblMachine14.Text = dt.Rows(13)("Machine_no").ToString
lblMachine15.Text = dt.Rows(14)("Machine_no").ToString
Next
End If
The problem is, when no data in rows 5 for example, the system will give an error.

Answer 1

Welcome to the site!
Before we address your problem, I would like to point out that:
"The problem is, when no data in rows 5 for example, the system will
give an error."
is too broad to really identify your issue.
It would be very helpful to also include the error message you are receiving.
Regarding your real problem, your code can be shortened with the use of DirectCast. You can try this one:
If dt.Rows.Count > 0 Then
For i = 0 To dt.Rows.Count - 1
DirectCast(Controls.Find("lblMachine" & i + 1, True)(0), Label).Text = dt.Rows(i).Item("MachineNo").ToString
Next
End If
Using For Loop in your code is a good start but you didn't integrate it at all. In the code above, you can see how i is being used.
Also dt is a DataTable right? DataTables are index-based so it's starting with zero(0). That's why you can notice in the the For Loop statement the dt.Rows.Count - 1.
Hope it helps.

Answer 2

https://learn.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/for-each-next-statement
Also try searching for:
Vb.net for each control loop
You will more than likely have to make a direct object reference using a List(Of Label)
Here is my take on it. Untested.
Dim machList As List(Of Label) = New List(Of Label)
For Each label As Label In GroupBox1.Controls
machList.Add(label)
Next label
For row As Integer = 0 To dt.Rows.Count
If dt.Row(row) <> Nothing Then
machList.Index(row).Text = dt.Rows(row)
End If
Next row

Answer 3

You are using i as a loop variable but you are not using to reference your labels.
You can try to put your labels in an array and then match them up to a row by index like this:
Dim labels = {lblMachine1, lblMachine2, lblMachine3, lblMachine4,...}
Dim sqlCmd As New SqlCommand("select distinct top 15 Machine_no from table5 ", conn)
Dim sqlDa As New SqlDataAdapter(sqlCmd)
sqlDa.Fill(dt)
If dt.Rows.Count > 0 Then
For i As Integer = 0 To dt.Rows.Count -1
dim row= dt.rows(i)
labels(i).text = row("Machine_no")
Next
End If
You can also use FindControl for windows formas #Allen points out. But when using for Web you need to implement a recursive version because the control you are looking for is usually nested within some other control.
private FindControlRecursive(control parent, string id) as control
if parent.id=id then return parent
for each child in parent.controls
control result = FindControlRecursive(child, id)
if not result is nothing then return result
next
end function
Then in your code:
Dim sqlCmd As New SqlCommand("select distinct top 15 Machine_no from table5 ", conn)
Dim sqlDa As New SqlDataAdapter(sqlCmd)
sqlDa.Fill(dt)
If dt.Rows.Count > 0 Then
For i As Integer = 0 To dt.Rows.Count -1
fincontrolrecursive("lblMachine" + i).text = dt.rows(i)("Machine_no")
Next
End If