VB.NET (Excel Two Columns > Conditional Comboboxes) - excel

Question

I'm searching for nearly two hours to find a solution on the following. In Excel I have two columns (One Column for Master Records and one Column for Slave Records). Basically, in Combobox1 I want to populate all the Master Records. If a selection is made for MasterRecord A, I want Combobox2 to only show me the SlaveRecords belonging to A and not the other records belonging to other Master Records.
I have the Interop Assembly added and Excel opened (there is a connection already). Your help is much appreciated!
Private Sub Combobox2_Populate()
'Start Excel Script to populate ComboBox2
Dim excel As Application = New Application
Dim w As Workbook = excel.Workbooks.Open(Filename:=databasestatus, [ReadOnly]:=True)
Dim sheet As Worksheet = w.Sheets("AIR_NL_1")
Dim StartRow As Integer
Dim TotalRows As Integer
ComboBox2.Items.Clear()
sheet.UsedRange.AutoFilter(Field:=9, Criteria1:=ComboBox1.SelectedItem, Operator:=XlAutoFilterOperator.xlFilterValues)
TotalRows = sheet.Range("A1").CurrentRegion.Rows.Count
For StartRow = 3 To TotalRows
If XlCellType.xlCellTypeVisible = True Then
ComboBox2.Items.Add(sheet.Range("H:H").Cells(StartRow, 1).Text)
End If
Next
w.Close(SaveChanges:=False)
End Sub

Answer 1

This might help you, or at least give you a basic idea:
Private Function ExcelToDataTable(ByVal fileExcel As String, _
Optional ByVal columnToExtract As String = "*", _
) As System.Data.DataTable
Dim dt As New System.Data.DataTable
Try
Dim MyConnection As System.Data.OleDb.OleDbConnection
Dim MyCommand As OleDbDataAdapter
Dim fileExcelType As String
'Chose the right provider
If IO.Path.GetExtension(fileExcel.ToUpper) = ".XLS" Then
fileExcelType = "Excel 8.0"
MyConnection = _
New System.Data.OleDb.OleDbConnection _
("provider=Microsoft.Jet.OLEDB.4.0;Data Source='" & fileExcel & "';Extended Properties=" & fileExcelType & ";")
Else
fileExcelType = "Excel 12.0"
MyConnection = _
New System.Data.OleDb.OleDbConnection _
("provider=Microsoft.ACE.OLEDB.12.0;Data Source='" & fileExcel & "';Extended Properties=" & fileExcelType & ";")
End If
'Open excel connection
MyConnection.Open()
'Populate DataTable
Dim myTableName = MyConnection.GetSchema("Tables").Rows(0)("TABLE_NAME")
MyCommand = New OleDbDataAdapter(String.Format("SELECT " & columnToExtract & " FROM [{0}] ", myTableName), MyConnection)
MyCommand.TableMappings.Add("Table", columnToExtract)
MyCommand.Fill(dt)
MyConnection.Close()
Catch ex As Exception
Err.Clear()
End Try
Return dt
End Function
As you can see, we have an optional parameter called myWhereStatement.
What does it mean?
You can specify its value when you call the function, otherwise its value will be an empty string
After that we can call ExcelToDataTable inside our Sub in order to populate the ComboBox as shown below:
Private Sub Combobox_Populate()
Dim filePath As String = "your_file_path"
ComboBox1.DataSource = ExcelToDataTable(filePath, "MasterRecord")
End Sub
Now you have your ComboBox1 filled with data, but the ComboBox2 is still empty.
We are going to handle the event of ComboBox1_SelectedValueChanged that means that every time you select an Item from the ComboBox1 it will programmatically fill the ComboBox2 with the propper items as shown below.
Private Sub ComboBox1_SelectedValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedValueChanged
Dim slaveRecords As System.Data.DataTable = ExcelToDataTable(filePath)
Dim dt As New DataTable
dt.Columns.Add("SlaveRecords")
For i As Integer = 0 To slaveRecords.Rows.Count
If ComboBox1.SelectedItem Is slaveRecords.Rows(i).Item(0) Then
dt.Rows.Add(slaveRecords.Rows(i).Item(1))
End If
Next
ComboBox2.DataSource = dt
End Sub
Remarks
As you can see the first call of ExcelToDataTable has only 2 parameters while the second one has 3 parameters. That's the optional parameter feature!
N.B.
As you can see I'm using alot of _ because of better code formatting. It means that a single statement will continue across multiple lines
If something isn't 100% clear ot you have any dubt feel free to ask in the comments below.