Understanding the Problem and Requirements

The provided Stack Overflow question and answer revolve around displaying data from a SQL table into synchronized ComboBox controls. The goal is to create an army builder list program for a historical miniatures strategy game, where 300 army lists are stored in separate SQL tables. Each table contains unit information such as name, shortname, type, quality, and cost.

The user wants to:

1. Display the data from each SQL table into ComboBox controls.
2. Synchronize all ComboBox controls to display the same row information.
3. Modify a Combobox’s Text property only based on the value of a specific cell in another table (quality unit).

Overview of Combobox Controls and Data Binding

Combobox controls are used to provide users with a list of values that can be selected from a dropdown menu. In .NET, these controls can be populated using various data sources, including databases.

Data binding is the process of linking a control’s properties to a data source. This allows the control to display and update data in real-time.

Creating Synchronized ComboBox Controls

To create synchronized ComboBox controls, we need to use a common data source for all controls. In this case, the SQL table data will serve as the shared data source.

We’ll use ADO.NET (ActiveX Data Objects) to interact with the SQL database and retrieve data from each table.

Step 1: Creating a Data Source

First, we need to create a DataTable object to hold the retrieved data.

Dim connection As New SqlConnection("Data Source=Server;Initial Catalog=OST;Integrated Security=True")
Dim dt As New DataTable

connection.Open()

sqlquery = "select * from liste1 Order By index_unité"

Dim SQL As New SqlDataAdapter(sqlquery, connection)
SQL.Fill(dt)

connection.Close()

This code connects to the database, executes a query that retrieves data from the liste1 table in ascending order of index_unité, and populates the dt DataTable object.

Binding ComboBox Controls to the Data Table

Next, we’ll bind each ComboBox control to the dt DataTable using the DataSource and DisplayMember properties.

ComboBoxNomUnités.DataSource = dt
ComboBoxNomUnités.DisplayMember = "nom_unité"

ComboBoxTypeUnités.DataSource = dt
ComboBoxTypeUnités.DisplayMember = "type_unité"

ComboBoxAbréviationUnités.DataSource = dt
ComboBoxAbréviationUnités.DisplayMember = "abréviation_unité"

ComboBoxCoutTotal.DataSource = dt
ComboBoxCoutTotal.DisplayMember = "cout_unité"

By setting the DataSource property to the dt DataTable, we’re linking each ComboBox control to the same data source. The DisplayMember property specifies which column of the DataTable should be displayed in the Combobox.

Synchronizing ComboBox Controls

To synchronize all ComboBox controls, we can use a technique called “databinding” or “data synchronization.” This involves updating the data source whenever one of the ComboBox controls changes its value.

One way to achieve this is by using the ValueChanged event handler for each ComboBox control. When an event is triggered, we update the dt DataTable with the new value and rebind all ComboBox controls.

ComboBoxNomUnités.ValueChanged += New EventHandler(AddressOf UpdateData)

We’ll implement the UpdateData method later in this article.

Modifying a Combobox’s Text Property

To modify a Combobox’s Text property only based on the value of a specific cell in another table (quality unit), we need to use a custom logic that checks the values and updates the text accordingly.

Let’s create a new method called UpdateQualityCombobox that will handle this logic.

Private Sub UpdateQualityCombobox()
    Dim S As String

    S = SQL("qualité_unité").ToString

    If S.Contains("médiocre") Then
        ComboBoxQualitéUnités.Text = "médiocre"
    ElseIf S.Contains("élite") Then
        ComboBoxQualitéUnités.Text = "élite"
    Else
        ComboBoxQualitéUnités.Text = "ordinaire"
    End If
End Sub

This method checks the value of the qualité_unité cell and updates the text property of the ComboBoxQualitéUnités Combobox accordingly.

Putting it all Together

Now that we’ve covered each component, let’s put them together to create our army builder list program.

Private Sub UpdateData(sender As Object, e As EventArgs)
    dt.Rows(e.NewValue.ToString()).ItemArray()
End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ComboBoxNomUnités.DataSource = dt
    ComboBoxTypeUnités.DataSource = dt
    ComboBoxAbréviationUnités.DataSource = dt
    ComboBoxCoutTotal.DataSource = dt

    UpdateData()

    UpdateQualityCombobox()
End Sub

In this code, we’re binding each Combobox control to the dt DataTable and updating the data source whenever a value changes. We’re also calling the UpdateData method when the form is loaded.

Conclusion

Displaying data from a SQL table into synchronized ComboBox controls requires some technical expertise in .NET programming. By understanding how to create and bind Combobox controls, synchronize their values, and update them dynamically, we can build powerful user interfaces that interact with databases seamlessly.

In this article, we’ve explored the basics of Combobox controls, data binding, and synchronization using ADO.NET and VB.NET. We’ve also created a custom logic to update a Combobox’s text property based on the value of another table cell (quality unit).

By applying these techniques, you can create your own army builder list program or other interactive applications that retrieve and display data from databases in real-time.

Last modified on 2023-11-29