Visual Basic

How to check the data type of user input?VB.Net

13-Dec-03 5:10

as topic, if i wan to create an array where the content of the array can be edited by form1 and form2, how i going to do it?
for example the content of array is {1,2,3}

form2 change the content to {1,2,4}

form1 also can see the changes in the array
where i should declare the array and wat is the format?
and how am i going to call the array in form1 and form2 for modification?
any help is greatly appreciated...thz...

How to Draw 3D charts

xprtguro13-Dec-03 2:40

xprtguro

13-Dec-03 2:40

how t to draw 3D or 2D charts in VB.net programatically.
i know how to draw it by adding it at design time.

Nothing ...........................................................

MJay13-Dec-03 2:23

Re: How to check the data type of user input?VB.Net

13-Dec-03 2:23

as topic, how do i check the data type (integer and string) of the user input in a textbox??
if i wan the user to input number 123, but he/she entered 123A, how i going to detect there is an error of input?? any help is greatly appreciate...

Colin Angus Mackay13-Dec-03 2:57

Re: How to check the data type of user input?VB.Net

13-Dec-03 2:57

Try something like:

Dim MyInteger As Int32

Try
    MyInteger = Convert.ToInt32(Me.TextBox1.Text)
Catch fex As FormatException
    ' Do something here to handle the input being wrong
    ' like "123A"
Catch oex As OverflowException
    ' Do something here to handle the input being out of
    ' range (i.e. It is a number but is it too big for
    ' an 32 bit integer.
End Try

--Colin Mackay--

"In the confrontation between the stream and the rock, the stream always wins - not through strength but perseverance." (H. Jackson Brown)

Enumerators in .NET: See how to customise foreach loops with C#

MJay13-Dec-03 6:44

Re: How to check the data type of user input?VB.Net

13-Dec-03 6:44

thanks again for help
this solution is works for checking integer, but seems like doest work on character?
i need to check a user input whether it is charecter type...
ur help is greatly appreciated...

Colin Angus Mackay13-Dec-03 7:02

Re: How to check the data type of user input?VB.Net

13-Dec-03 7:02

Sorry, I'm don't quite understand. I thought you wanted to check that the input was an integer. Is this another control you want to check? Can you be more specific about what you need it to do.

Thanks.

--Colin Mackay--

Charlie Williams13-Dec-03 9:35

Charlie Williams

13-Dec-03 9:35

One way to validate user input is using regular expressions. Regexes can get pretty complicated if you need them to do more advanced validation, but simple things like making sure only numbers are input are simple enough.

This test looks for the beginning of a line, followed by one or more numbers, followed by the end of the line:

Imports System.Text.RegularExpressions

<br />
Dim re as new Regex("^\d+$")<br />
If re.IsMatch(myTextBox.Text) Then<br />
  'Input passed the test<br />
Else<br />
  'Failed<br />
End If<br />

To accept only non-numbers: "^\D+$"
To accept only strings in the format 123A: "^[\d]{3}[A-Z]$"

There are more variations than you can shake a stick at. You could, for example, make sure input is in the format of a US social security number or a phone number or a URL or whatever else you can think of.

Charlie

Here I am. Love me.

Re: How to check the data type of user input?VB.Net

MJay13-Dec-03 21:44

Re: How to check the data type of user input?VB.Net

13-Dec-03 21:44

thanks for help
what if i wan to accept only character A-Z and a-z ?(no included symbols such as @#*%_)
wat is the regularexpression format?

To accept only non-numbers: "^\D+$"

this format accept only character but it also accept symbols which i dun wan be included...
ur help is greatly appreciated...

Charlie Williams14-Dec-03 8:28

Charlie Williams

14-Dec-03 8:28

Anything in square brackets will match one character. The hyphen specifies a range. For example, [a-m] will match 'a' or 'g', etc., but not 'n' or 'A' (It's case sensitive, although there's an \i switch to compare in a case insensitive manner.) So [a-zA-Z] is what you're looking for. \w is similar, but also matches _ and 0-9

Mastering Regular Expressions[^] by Jeffrey E. F. Friedl is a great book about regexes. The author uses perl for the bulk of the book, but there is a section specific to .net and .net uses mostly perl flavored regexes, anyway. (Though in an OO way). If you don't use them enough to justify purchasing a book, VS.Net's online help has quite a bit of info on them.

Charlie

Here I am. Love me.

How to disable item editing in combobox?vb.Net

MJay13-Dec-03 2:19

13-Dec-03 2:19

the default setting of combo box enable user to edit the listed in combobox just like normal textbox, but i cant find any property that can disable this option, i wan the combobox to be read-only to user...how i going to do that?? anyone can help me??VB.Net

Colin Angus Mackay13-Dec-03 3:12

13-Dec-03 3:12

Try this:

Me.ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList

Or just set it in the designer.

The defintions for ComboBoxStyle are:
DropDown The text portion is editable. The user must click the arrow button to display the list portion.
DropDownList The user cannot directly edit the text portion. The user must click the arrow button to display the list portion.
Simple The text portion is editable. The list portion is always visible.

--Colin Mackay--

MJay13-Dec-03 6:07

13-Dec-03 6:07

thanks man, ur solution works!
however seems like the combobox will no default value when form loaded, the combobox is empty
how i going to set the first item in the combobox to be the default item when form is loaded?

Colin Angus Mackay13-Dec-03 6:16

13-Dec-03 6:16

Use SelectedIndex or SelectedText

--Colin Mackay--

MJay13-Dec-03 21:49

Passing variable between parent/child forms

13-Dec-03 21:49

thanks man, u helped me alot, i am a beginner in vb.net
hope the questions i asked wont make u feel boring...

MadCow12-Dec-03 16:00

MadCow

12-Dec-03 16:00

ok, I'm completely new to VB and have come up with a problem on something that I think it really easy.

What I have are 2 forms, form1 and form2. Form2 gets called from a context popup on a listview on form1. Now, on form2 I have a textbox variable that I want transfered back to the listview on form1 when you click on the OK button on form2. However I am unable to access the listview on form1 from form2. I figure it's a scope issue. I have found a work around on MSDN that works, but to me it seems wrong.

Private Sub MenuItem6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MenuItem6.Click
Dim frmAction As New fclsRoomAction

frmAction.ShowDialog()
lstRoomAction.Items.Add(frmAction.tbActionDesc.Text)

End Sub

Here I have called my 2nd form, but I set my listview with the variable AFTER I have closed the form. Just dosn't seem right to me because I have closed the file BEFORE I read my variable. I think this has something to do with the way .net does garbage upkeep. I'm not sure. Like I said I'm new to this.

So... Now I ask. Is this the standard way of passing variables between forms or is there a more elegent way of doing it. I was originally hoping to be able to do it on form2 as there I can create 2 buttons, accept and cancel, which determine whether I copy the variable over or not. But as I cannot access my listview on form2 I was unable to do this.

Hopefully this makes sense. Thanks.

Randy.

Colin Angus Mackay13-Dec-03 2:47

13-Dec-03 2:47

The general way I'd do this would be to create a property for each value that I want to expose on Form2. Create an event handler for the Closing event and populate the values that the propery will expose.

e.g.

'The value to return to the other form
Private myValue As String

' This is the propery that exposes the value needed by
' the other form
Public ReadOnly Property ValueForOtherForm() As String
    Get
        Return Me.myValue
    End Get
End Property

' When the Form closes ensure that the value is transered so
' that the property works.
Private Sub Form2_Closing(ByVal sender As Object, _
            ByVal e As System.ComponentModel.CancelEventArgs) _
            Handles MyBase.Closing
    myValue = Me.tbSomeControl.Text
End Sub

Then, back in Form1, you can do this:

Private Sub MenuItem6_Click(ByVal sender As System.Object, _
                ByVal e As System.EventArgs) Handles MenuItem6.Click
    Dim frmAction As New fclsRoomAction
    frmAction.ShowDialog()
    lstRoomAction.Items.Add(Form2.ValueForOtherForm)
End Sub

I hope this helps.

--Colin Mackay--

MadCow13-Dec-03 13:58

MadCow

13-Dec-03 13:58

Thanks for the help. I'm pretty new to the oop aspect of VB, but I assume thats what you were describing there as I know that properties in objects have get/set.

So after spending some time reading up on objects and browsing your code, I understand whats going on, but it troubles me how I'm able to reference a variable from a form that dosn't exist anymore. It's been closed after all and all variable on that form should be gone. It just feel wrong for me to code like that. Is this how VB.net is normally done? Can't you reference a control (eg. textbox) that exists on form1 from form2 and put it directly into it's text property without having to create storage variables? I can't seem to get it to work. I must be missing something...

Randy.

Colin Angus Mackay13-Dec-03 14:50

13-Dec-03 14:50

MadCow wrote:
it troubles me how I'm able to reference a variable from a form that dosn't exist anymore

The form "object" exists, but the controls don't. One of the more difficult concepts to understand is that there is managed (that's .NET) and unmanaged (that's Win32 API) stuff going on. The .NET Framework hides most of the Win32 implementation but you do get the occasional glimps that it is there sitting in the background.

Let me try and explain better. The WinForms part of .NET Framework is a wrapper around the Win32 API which is what drives Windows. When the form is closed .NET cleans up all the controls by disposing of them immediately rather than wait for the garbage collector to do it. [The way controls work in Win32 mean there is actually limited space for them so it is very important to let the system know when you are done with them]. The Form object still exists, but the underlying (Win32) controls on it don't because .NET has told Windows they are no longer required. The managed things, like the exposed string propery do still exist because they have no unmanaged element.

MadCow wrote:
It's been closed after all and all variable on that form should be gone

Just because a form has been closed doesn't mean it doesn't exist. It just means that the User Interface part is, well, "Closed".

MadCow wrote:
Is this how VB.net is normally done?

Personally, I'd create a controller object to store all that stuff and access it from the various forms that need it. I don't know if this is going to be too much information to take in at this point, but you could also read this article about the Model-View-Controller pattern[^] on Microsoft's web site. It also has links to other related articles about how to write good software.

MadCow wrote:
Can't you reference a control (eg. textbox) that exists on form1 from form2 and put it directly into it's text property without having to create storage variables? I can't seem to get it to work

I'm guessing that you need to cast the variable referencing form1 into the correct type. You probably have the base class in the .NET framework and you need to cast it to the specific type to access anything that is added in the derived class.

I'm sorry that I am not able to recommend a good book on OO concepts, I learned all that stuff years ago and all I have is lecture notes. However the article mentioned above is in a section of the Microsoft Web site[^] that contains a lot of examples of good Object Orientation.

I hope all this helps and my length reply, and even lengthier set of further reading material has not put you off.

--Colin Mackay--