Auto fill Combo Boxs with data from SQL server database VB.Net - sql-server

Question

l have a data source that contains two columns
block_name total_lands
A-0 5
A-1 15
A-2 18
A-3 18
And I have two combo boxes one for the block name and the other for the no of lands
the first one is loaded with the block names
Private Sub LoadItems()
SQL.ExecQuery("SELECT block_name FROM blocks;")
For Each i As DataRow In SQL.DBDTable.Rows
ComboBox1.Items.Add(i("block_name"))
Next
End Sub
I want the second one to be loaded with numbers from 1 to whatever is in the data source row total_lands
For example if the user chose the block name as A-1 I want the second combo box to have the items from 1 to 15 add in it
My code trying to do so
Private Sub LoadNoOfLands()
SQL.AddParam("#blockname", ComboBox1.Text)
SQL.ExecQuery("SELECT totla_lands FROM blocks WHERE total_lands LIKE #blockname;")
For Each no As DataRow In SQL.DBDTable.Rows
Dim lands As Integer = no("block_lands")
'For Each i As Integer In lands
'
'
'Next
Next
End Sub

Answer 1

Load required data at once and use Enumerator.Range to generate collection of numbers for second combobox
Public Class Block
Public ReadOnly Property Name As String
Public ReadOnly Property TotalLands As Integer
Public ReadOnly Property Lands As Integer()
Public Sub New(name As String, totalLands As Intger)
Name = name
TotalLands = totalLands
Lands = Enumerable.Range(1, totalLands).ToArray()
End Sub
End Class
Private Function LoadBlocks() As Block()
Dim query = "SELECT block_name, total_lands FROM table"
Dim rows = SQL.ExecuteQuery(query)
Return rows.AsEnumerable().
Select(Function(row) New Block(row.Field(Of String)("block_name"), row.Field(Of Integer)("total_lands"))).
ToArray()
End Function
Private Sub SetupComboBox()
cmbBlocks.DisplayMemeber = "Name"
cmbBlocks.DataSource = LoadBlocks()
End Sub
Private Sub cmbBlocks_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles cmbBlocks.SelectionChangeCommitted
Dim combobox As ComboBox = DirectCast(sender, ComboBox)
Dim block As Block = DirectCast(combobox.SelectedValue, Block)
cmbLands.DataSource = block.Lands
End

Answer 2

I have come up with a simple answer
Private Sub LoadNoOfLands()
cmbLands.Items.Clear()
SQL.AddParam("#blockname", cmbBlocks.Text)
SQL.ExecQuery("SELECT total_lands FROM blocks WHERE block_name LIKE #blockname;")
If SQL.HasException(True) Then Exit Sub
For Each i As DataRow In SQL.DBDTable.Rows
Dim lands = i("total_lands")
Dim r = 1
For r = 1 To lands
cmbLands.Items.Add(r).ToString()
Next
Next
End Sub
This function just adds number to combobox form 1 to the total_lands value

Answer 3

I created a class for the data.
Public Class Block
Public Property Name As String
Public Property TotalLands As Integer
Public Sub New(BlockName As String, Lands As Integer)
Name = BlockName
TotalLands = Lands
End Sub
Public Overrides Function ToString() As String
Return Name
End Function
End Class
The combo box will call .ToString on the items to determine what to display.
We get the data from the database and add it to the List(Of Block)
Public Function FillBlocksList() As List(Of Block)
Dim lst As New List(Of Block)
Using cn As New SqlConnection("Your connection string"),
cmd As New SqlCommand("Select block_name, total_lands From BlockTable;", cn)
cn.Open()
Using reader = cmd.ExecuteReader
Do While reader.Read
Dim b As New Block(reader.GetString(0), reader.GetInt32(1))
lst.Add(b)
Loop
End Using
End Using
Return lst
End Function
To fill the first combo we get the list then loop through it adding the Block objects to the combo. You would probably call this from Form.Load.
Public Sub FillBlocksCombo()
Dim lst = FillBlocksList()
For Each item In lst
ComboBox1.Items.Add(item)
Next
End Sub
To fill the second combo cast the select item back its underlying type, Block and use the TotalLands property to add the numbers.
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
Dim NumberOfLands = DirectCast(ComboBox1.SelectedItem, Block).TotalLands
For i = 1 To NumberOfLands
ComboBox2.Items.Add(i.ToString)
Next
End Sub