How to Setup A Combox , always will with same data, as a user control to be used on multiple forms-CodePudding

I have a ComboBox that I use on multiple WinForms. Instead of dropping a ComboBox on each WinForm and then filling the ComboBox with data from a DataTable on each individual WinForm, couldn't I create a User Control (ComboBox) that has the data populated already and just use that UC on my Winforms?

Below is how I fill the data for each individual combobox now. (I have a public class for the sql stuff)

The Variable SQL comes from a Class called SQLControl. the Class has all the sql connection stuff.

Public Sub Fillcombobox()

    sql.AddParam("@ExaminerType", 3)
    sql.ExecQuery("MyStoredProcedure")
    ComboBoxExaminer.ValueMember = "Examiner_ID"
    ComboBoxExaminer.DisplayMember = "Last_Name"
    ComboBoxExaminer.DataSource = sql.DBDT
End Sub

Private Sub MyWinform_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Call Fillcombobox()
End Sub

CodePudding user response：

You can put a small Class Examiner

Public Class Examiner
    Public Property Examiner_ID As Integer
    Public Property Last_Name As String
    Public Sub New(ID As Integer, lname As String)
        Examiner_ID = ID
        Last_Name = lname
    End Sub
End Class

Then, when the first form loads, get the data in a list declared in a module so it can be accessed from any form in the application. Of course, you may have other things in the Module.

Module Module1
    Public ExaminerData As New List(Of Examiner)
End Module

Private Sub MyWinform_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    FillExaminerList()
    ComboBoxExaminer.ValueMember = "Examiner_ID"
    ComboBoxExaminer.DisplayMember = "Last_Name"
    ComboBoxExaminer.DataSource = ExaminerData
End Sub

Any other form that needs the data to fill a combo box can use ExaminerData. You only call FillExaminerList once at the beginning of the application. There is only a single hit on the database.

Private OPConStr As String = "Your connection string."

Private Sub FillExaminerList()
    Dim dt As New DataTable
    Using cn As New SqlConnection(OPConStr),
            cmd As New SqlCommand("MyStoredProcedure", cn)
        cmd.Parameters.Add("@ExaminerType", SqlDbType.Int).Value = 3
        Using reader = cmd.ExecuteReader
            dt.Load(reader)
        End Using
    End Using
    For Each row As DataRow In dt.Rows
        Dim ex As New Examiner(CInt(row("Examiner_ID")), row("Last_Name").ToString)
        ExaminerData.Add(ex)
    Next
End Sub