VB.NET Need guide on error checking using MessageBox - arrays

Question

Lets say I have a form with 100 textboxes, comboboxes and other controls and I want to check if any of the controls is empty. When I click on 'OK' button, I want the messagebox to show a list of errors example Textbox1 is empty, Textbox30 is empty and such.
I can achieve this by doing the tedious method where I check textbox1 and messagebox is shown, check textbox2 and messagebox is shown again and so on.
I want the messagebox to show only once. How can I achieve this?
What I have did is that I set up an array and store all the error messages to be shown later by selecting (example Msgbox(errMessages(3) + Environment.newline + errMessages(30)) and I know this is not the right way to do it as well.
Please and thank you in advance.

Answer 1

Here is a direct answer to your question:
You can store the empty controls in a list, and at the end create the message like this:
Dim empty_controls = New List(Of Control)
If TextBox1.Text = String.Empty Then
empty_controls.Add(TextBox1)
End If
If TextBox2.Text = String.Empty Then
empty_controls.Add(TextBox2)
End If
Dim result As String = String.Join(
Environment.NewLine,
empty_controls.Select(Function(c As Control) c.Name + " is empty"))
MessageBox.Show(result)
Here is even a better way to detect which text boxes are empty:
Dim empty_controls = New List(Of Control)
//The following line will search through all text boxes on the form
empty_controls.AddRange(
Controls.OfType(Of TextBox).Where(Function(c As Control) c.Text = String.Empty))
//Here you can add other kinds of controls with their own way of determining if they are empty
Dim result As String = String.Join(
Environment.NewLine,
empty_controls.Select(Function(c As Control) c.Name + " is empty"))
MessageBox.Show(result)