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Check Values in an Array if Null

Posted on 2008-10-18
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Last Modified: 2012-05-05
I'm trying to simplify my coding by putting all of my requirements in ONE potential line of code instead of assigning if functions to each silly variable i have, which leads me to my question.

I have a UI with text boxes, some of which can be left empty, some which cannot. What I'm looking for is a way to add an array containing those variables that cannot be empty, and if this is possible, for the program to check each variable (text box) for any indication that it's null, if so, throw up a msgbox stating the exact box which is empty before it writes anything to the db.

I'm currently working with a few basic text boxes. FirstName, LastName, DOB, Address, PhoneNumber.

Any help would be greatly appreciated!!
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Question by:Arka3L
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Expert Comment

by:Mike Tomlinson
ID: 22750005
WinForms or WebForms?  ...and what version VB.Net?
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Author Comment

by:Arka3L
ID: 22750078
WinForm and 2005, sorry.
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LVL 85

Expert Comment

by:Mike Tomlinson
ID: 22750413
You could do something like this:
(...there are many ways to approach this though!...)
Public Class Form3
 
    Private RequiredEntries() As String = {"LastName", "DOB", "PhoneNumber"}
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim tb As TextBox
        Dim ctl As Control
        For Each ctlName As String In RequiredEntries
            ctl = GetControlByName(ctlName)
            If Not IsNothing(ctl) AndAlso TypeOf ctl Is TextBox Then
                tb = DirectCast(ctl, TextBox)
                If tb.Text.Trim.Length = 0 Then
                    MessageBox.Show(ctlName, "Missing Entry", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                    tb.Focus()
                    Exit Sub
                End If
            End If
        Next
 
        ' ...if you get here then the TextBoxes have been properly filled out...
        MessageBox.Show("All Required Entries have been Filled Out")
    End Sub
 
    Private Function GetControlByName(ByVal ctlName As String) As Control
        Dim matches() As Control = Me.Controls.Find(ctlName, True)
        If matches.Length > 0 Then
            Return matches(0)
        Else
            Return Nothing
        End If
    End Function
 
End Class

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Author Comment

by:Arka3L
ID: 22750634
Wow! That was absolutely perfect and more than I even expected. It's almost a perfect solution to my problem.

However just two things, 1 which I can't figure out.

I'm not sure which version you are using but the  

Private RequiredEntries() As String = {"LastName", "DOB", "PhoneNumber"}

Had to be

Dim RequiredEntries() As String = {"LastName", "DOB", "PhoneNumber"}

It wasn't happy with the Private at all, it was unusable locally..? Now I understand that we're telling the compiler that the names i've given to the text boxes, which are also my variables, are stated in the initial RequiredEntries.

However, when it comes to returning the result to the MsgBox stating that we've missed a field, it uses the name of our Variable on the MsgBox e.g. FirstName. Because this is the variable and is being contained in ctlName, is there a way that I can change the text to First Name? DOB to Date of Birth etc.

It's extremely complicated for me reading all this at first but i'm slowly grasping the concept.

Thank you for your help!
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Author Comment

by:Arka3L
ID: 22750793
Ignore my incompetence with the first problem i referenced with the private vs dim, it was inside the button sub instead of it being outside lol.
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Accepted Solution

by:
Mike Tomlinson earned 500 total points
ID: 22751194
Again, lots of ways to do it...here is one:
Public Class Form1
 
    Private RequiredFields As New Dictionary(Of String, String)
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim values() As String
        Dim RequiredEntries As String = "LastName,Last Name|DOB,Date of Birth|PhoneNumber,Phone Number"
        For Each pair As String In RequiredEntries.Split("|")
            values = pair.Split(",")
            RequiredFields.Add(values(0), values(1))
        Next
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim tb As TextBox
        Dim ctl As Control
        For Each ctlName As String In RequiredFields.Keys
            ctl = GetControlByName(ctlName)
            If Not IsNothing(ctl) AndAlso TypeOf ctl Is TextBox Then
                tb = DirectCast(ctl, TextBox)
                If tb.Text.Trim.Length = 0 Then
                    Dim msg As String = RequiredFields.Item(ctlName)
                    MessageBox.Show(msg, "Missing Entry", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                    tb.Focus()
                    Exit Sub
                End If
            End If
        Next
 
        ' ...if you get here then the TextBoxes have been properly filled out...
        MessageBox.Show("All Required Entries have been Filled Out")
    End Sub
 
    Private Function GetControlByName(ByVal ctlName As String) As Control
        Dim matches() As Control = Me.Controls.Find(ctlName, True)
        If matches.Length > 0 Then
            Return matches(0)
        Else
            Return Nothing
        End If
    End Function
 
End Class

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Author Comment

by:Arka3L
ID: 22751246
Absolute God send!
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