How to validate Empty Textboxes, ComboBox and Date in vb - mysql

Question

I have created a form that saves sales data into the database and if the user has not filled all fields, It should either display an error message or just highlight the empty textbox. In my case, I made the textbox be highlighted if empty but some of the textboxes such as the date and two of the combo boxes are not highlighted. If the textbox is not empty then save data which I already did code for saving data to the database. I just don't know how to structure to put the else statement that if the textbox isn't empty then save data. Screenshot: https://snipboard.io/t5keMo.jpg
This is my code:
Public Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
Dim txt As Control
Dim combo As New Control
' While
For Each txt In Panel1.Controls
If TypeOf txt Is TextBox Then
If txt.Text = "" Then
txt.BackColor = Color.Yellow
txt.Focus()
End If
End If
Next
For Each combo In Panel1.Controls
If TypeOf combo Is ComboBox Then
If combo.Text = "" And combo.Text = "" Then
combo.BackColor = Color.Yellow
combo.Focus()
End If
End If
Next
For Each Dt In Panel1.Controls
If TypeOf Dt Is Date Then
If Dt.Text = "" Then
Dt.BackColor = Color.Yellow
Dt.Focus()
End If
End If
Next
' End While
End Sub
Save data:
Public Sub save_data()
' load_table()
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=golden_star"
Dim READER As MySqlDataReader
Try
MysqlConn.Open()
Dim Query As String
If (MessageBox.Show("Do you want to save the changes?", "Save Changes", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = DialogResult.Yes) Then
Query = "insert into golden_star.sales (date,brand,size,selling_unit_price,cost_unit_price,quantity,cost_of_goods,profit,total_cost_price) values ('" & DateTimePicker.Text & "','" & ComboBox1.Text & "', '" & ComboBox2.Text & "', '" & txtSelling.Text & "', '" & txtCostPrice.Text & "', '" & ComboBox3.Text & "', '" & txtTotalSell.Text & "', '" & txtProfit.Text & "',
'" & txtCp.Text & "')"
Command = New MySqlCommand(Query, MysqlConn)
MessageBox.Show("Daily Sales Entered Successfully")
READER = Command.ExecuteReader
MysqlConn.Close()
End If
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
MysqlConn.Dispose()
End Try
End Sub

Answer 1

You should definitely be using the right control for the right data type. For example, do not use a TextBox for a DateTimePicker and use an ErrorProvider to indicate if a control has any errors.
Here is a very rudimentary example:
Private _errorProvider As New ErrorProvider()
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' loop over every control in your Panel
For Each ctrl In Panel1.Controls.OfType(Of Control)()
' wire up the Validated event for the control
AddHandler ctrl.Validated, Sub(innerSender As Object, innerE As EventArgs)
' if the control does not have a value in it's Text property, then set an error
Dim validatedControl = DirectCast(innerSender, Control)
Dim validationError = If(String.IsNullOrWhiteSpace(validatedControl.Text), "Required", String.Empty)
_errorProvider.SetError(validatedControl, validationError)
End Sub
Next
End Sub
Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
Dim anyErrors = False
' loop over the controls and select them to force validation
For Each ctrl In Panel1.Controls.OfType(Of Control)()
ctrl.Select()
If (Not String.IsNullOrWhiteSpace(_errorProvider.GetError(ctrl))) Then
anyErrors = True
End If
Next
' if any control has an error, then stop execution of the method
If (anyErrors) Then
Return
End If
' if there are not any validation errors, then continue with business logic
End Sub