How to Clear ComboBox with DataSource in VB.Net and MySQL Database

Submitted by janobe on Monday, September 10, 2018 - 16:58.

This time, I will teach you how to clear ComboBox with DataSource in VB.Net and MySQL database. Removing list of records in the combo box that has a data source is a bit hard to do especially for beginners in programming. So I made this tutorial to help you clear all the data that’s inside the combo box in just a click. Below are the procedures on how to make it work.

Creating the Database

Create a database and named it "test"

Create database test

Then, create a table in the database that you have created.

CREATE TABLE `test`.`tblrecords` ( `RecordID` INT NOT NULL AUTO_INCREMENT ,`Subject` VARCHAR(90) NOT NULL , `Course` VARCHAR(90) NOT NULL , `Category`VARCHAR(90) NOT NULL , PRIMARY KEY (`RecordID`)) ENGINE = InnoDB; 

Creating an Application

Step 1

Open Microsoft Visual Studio 2015 and create a new window form application. Then do the form just like this. psComboBox1

Step 2

Double click the form to fire the code editor.

Step 3

In the code editor, set the import above the Public Class.

Imports MySql.Data.MySqlClient

Step 4

Initialize all the classes that are needed inside the Public Class.

  Dim con As MySqlConnection = New MySqlConnection("server=localhost;user id=root;password=;database=test;sslMode=none")
    Dim cmd As MySqlCommand
    Dim da As MySqlDataAdapter
    Dim dt As DataTable
    Dim sql As String

Step 5

Create a sub procedure for retrieving the data in the combobox.

Private Sub fillComboBox(sql As String, feilds As String, combo As ComboBox)
        Try
            con.Open()
            cmd = New MySqlCommand
            With cmd
                .Connection = con
                .CommandText = sql
            End With
            da = New MySqlDataAdapter
            da.SelectCommand = cmd
            dt = New DataTable
            da.Fill(dt)
 
            With combo
                .DataSource = dt
                .DisplayMember = feilds
            End With
 
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            con.Close()
            da.Dispose()
        End Try
    End Sub

Step 6

Do this following code for retrieving data on the first load of the form.

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        fillComboBox("select * from tblrecords", "Subject", cboSubject)
 
        fillComboBox("select * from tblrecords", "Course", cboCourse)
 
        fillComboBox("select * from tblrecords", "Category", cboCategory)
    End Sub

Step 7

Go to the design views and double click the “Clear All” button to fire the click event handler of it. After that, create a code for clearing the entire combo box with data source.

Try
 
            For Each combo In Me.Controls
                If TypeOf combo Is ComboBox Then
                    combo.DataSource = Nothing
                End If
            Next combo
 
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

Note: add mysql.data.dll for the references to access MySQL Library The complete sourcecode is included. You can download it and run it on your computer. For more question about this article. You can contact me @ Email – [email protected] Mobile No. – 09305235027 – TNT FB Account – https://www.facebook.com/onnaj.soicalap

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