Print input from user in WPF VB - wpf

Question

I'm working on project where the user will enter a JobNumber, say (J000001), and when the user hits print the jobnumber will print. With the code below, I'm able to print the numbers, say (001), but I want the user to enter the actual JobNumber (J000001). Any help on this is greatly appreciated.
When I enter the JobNumber (J000001), I get the following error message:
'Invalid CastException was unhandled'
Conversion from string "J000001" to type boolean is not valid.
Below is my VB Code:
Imports System.Globalization
Imports System.Drawing.Printing
Imports System.Drawing
Class MainWindow
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
AddHandler printDocument1.PrintPage, AddressOf printDocument1_PrintPage
End Sub
'Declaration the global variables
Private paperSize As New PaperSize("papersize", 300, 500)
'set the paper size
Private totalnumber As Integer = 0
'this is for total number of items of the list or array
Private itemperpage As Integer = 0
'this is for no of item per page
Private printDocument1 As New PrintDocument()
Private printDialog1 As New System.Windows.Forms.PrintDialog()
Private DefaultFont As New Font("Calibri", 20)
Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
If txtStart.Text Then
itemperpage = 1
totalnumber = txtStart.Text
printDialog1.Document = printDocument1
printDocument1.DefaultPageSettings.PaperSize = paperSize
printDialog1.ShowDialog()
'printDocument1.PrinterSettings.PrinterName = "";
printDocument1.Print()
Else
MessageBox.Show("Invalid number")
End If
End Sub
Private Function CheckNumber(str As String)
Dim Num As Double
Return Double.TryParse(str, Num)
End Function
'Define the Printpage event of the printdocument
Private Sub printDocument1_PrintPage(sender As Object, e As System.Drawing.Printing.PrintPageEventArgs)
Dim currentY As Single = 10
While totalnumber <= CInt(txtStart.Text)
' check the number of items
e.Graphics.DrawString(totalnumber.ToString(), DefaultFont, System.Drawing.Brushes.Black, 50, currentY)
'print each item
currentY += 20
' set a gap between every item
totalnumber += 1
'increment count by 1
If itemperpage < 1 Then
' check whether the number of item(per page) is more than 1 or not
itemperpage += 1
' increment itemperpage by 1
' set the HasMorePages property to false , so that no other page will not be added
e.HasMorePages = False
Else
' if the number of item(per page) is more than 1 then add one page
itemperpage = 1
'initiate itemperpage to 0 .
If totalnumber <= Convert.ToInt32(txtStart.Text) Then
e.HasMorePages = True
End If
'e.HasMorePages raised the PrintPage event once per page .
'It will call PrintPage event again
Return
End If
End While
End Sub
End Class
XAML code
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="175" Width="303">
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="1.5*" />
</Grid.ColumnDefinitions>
<Label Content="Start Number:" />
<TextBox x:Name="txtStart" Grid.Column="1" />
<Button Grid.Row="2" Grid.ColumnSpan="2" Content="Print" Click="Button_Click" />
</Grid>
</Window>

Answer 1

The issue is your If statement in the Button_Click method.
If txtStart.Text Then
The If takes a boolean, but you are passing it a string. VB.Net is trying to convert the string to a boolean. 001 works, because it can convert that. J000001 is not able to be converted to a boolean.
Do you mean to check if there is a value entered?
If !String.IsNullOrWhiteSpace(txtStart.Text) Then
You will also run into a similar issue when assigning the value to totalnumber.

Answer 2

You are comparing the value of the text box as a boolean, and then assigning the value of your Text Box to a variable of type Integer.
If txtStart.Text Then
should probably be something like:
If !String.IsNullOrEmpty(txtStart.Text) Then
And then if you job numbers are alpha numeric, use a variable of type String instead of Integer.