Accessing Variables in Partial Public Class : The Official Microsoft ASP.NET Forums

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hrdfsique

Member

31 Points

Accessing Variables in Partial Public Class

Apr 10, 2009 11:06 PM|LINK

I am currently working on a project of "interpreting" C# into VB. The project involves adding images to a database, retrieving images from the database and presenting them in thumbnails.

Right now I have the following Public Class with the Variable that needs to be assigned:

VB:

Imports System.Data
Imports System.Drawing
Imports System.IO


Partial Public Class ThumbFromID


    Inherits System.Web.UI.Page
    '*** instances
    '   constants used to create URLs to this page
    Public Const PAGE_NAME As String = "ThumbFromID.aspx"
    '   the image primary key for use when getting image data from database
    Public Const IMAGE_ID As String = "img_pk"
    '   height of the thumbnail created from the original image
    Protected THUMBNAIL_SIZE As Integer
    '   true if using thumbnail THUMBNAIL_SIZE for height, else it is used for width
    Protected USE_SIZE_FOR_HEIGHT As Boolean
    '*/End Instances

The C# Equivilant is:

public partial class ThumbFromID : System.Web.UI.Page
{
    #region Instance Fields
    // constants used to create URLs to this page
    public const String PAGE_NAME = "ThumbFromID.aspx";
    //the image primary key for use when getting image data from database
    public const String IMAGE_ID = "img_pk";
    // height of the thumbnail created from the original image
    public static int THUMBNAIL_SIZE;
    // true if using thumbnail THUMBNAIL_SIZE for height, else it is used 
    // for width
    public static bool USE_SIZE_FOR_HEIGHT;
    #endregion

In the default.aspx.vb code page I am trying to access the THUMBNAIL_SIZE variable. My logic tells me that all I would have to do is call it like this: ThumbFromID.THUMBNAIL_SIZE = "value", and indeed that works in C#.

How do I do this in VB? The page is not recoginizing ThumbFromID as a public class...

Here is the C# code that works:

public partial class _Default : System.Web.UI.Page
{
    #region instance fields
    //instance fields
    protected System.Web.UI.WebControls.Image imgImage;
    private int THUMBNAIL_SIZE = 60;
    #endregion

    protected void Page_Load(object sender, EventArgs e)
    {
    }

    /// &lt;summary&gt;
    /// Creates an image, by querying the SQL database with the given img_pk
    /// parameter. The query will return a byte[] array, which represents the 
    /// image. This byte[] array is then converted into an image and added to 
    /// the placeholder control "plImage" which is on this page
    /// </summary>
    /// <param name="img_pk">The primary key to fetch the image data for</param>
    private void createImageFromDBBytes(int img_pk)
    {

        ThumbFromID.THUMBNAIL_SIZE = this.THUMBNAIL_SIZE;                           /// -----> this is does not work for vb
        ThumbFromID.USE_SIZE_FOR_HEIGHT = false;                                           /// -----> how do we call this variable from the Partial Public Class?
        imgImage = new System.Web.UI.WebControls.Image();
        // set the source to the page that generates the thumbnail image
        imgImage.ImageUrl = ThumbFromID.PAGE_NAME + "?" +
            ThumbFromID.IMAGE_ID + "=" + img_pk;
        litException.Visible = false;
        plImage.Controls.Clear();
        plImage.Controls.Add(imgImage);
    }

Your help will be greatly appreciated.

Moved by SGWellens on Apr 11, 2009 12:20 AM
Edited by hrdfsique on Apr 11, 2009 04:24 PM

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hrdfsique

Member

31 Points

36 Posts

Re: Accessing Variables in Partial Public Class

Apr 11, 2009 04:29 PM|LINK

Is the above not clear enough or does nobody know how to do this?

C'mon, I know there is someone that can help with this... I am just a beginner, there has got to be hope...

Just to be clear: How can I access the Partial Public Class ThumbFromID - and the variable THUMBNAIL_SIZE from the page class Default.aspx(.vb)?

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asifchouhan

Participant

1637 Points

298 Posts

Re: Accessing Variables in Partial Public Class

Apr 11, 2009 04:48 PM|LINK

view this blog

http://www.devx.com/dotnet/Article/22603

U need to create the object of the first class first and then acces the variable value from that object

or

C# you should add the keyword global along with a namespace alias qualifier :: as in the following syntax

global::System.Double mydouble;

Above one is used for the fields or variables

Regards

Asif

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Please remember to click “Mark as Answer” on the post that helps you.
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hrdfsique

Member

31 Points

36 Posts

Article 22603 Does not give a solution for this problem.

Apr 13, 2009 05:52 PM|LINK

I don't understand the logic between what the article describes and what I am trying to accomplish...

According to the article my code would look like this:

Imports System.Data
Imports System.IO
Imports System.Drawing


Partial Public Class Admin_Default
    Inherits System.Web.UI.Page


    '*** declaring instances
    Protected imgImage As Image
    Private thumnail_size As Integer = 60
    '*/End instances

    Private Sub createImageFromDBBytes(ByVal img_pk As Integer, ByVal THUMBNAIL_SIZE As Integer, ByVal USE_SIZE_FOR_HEIGHT As Boolean)  '***Not Correct***
        THUMBNAIL_SIZE = Me.thumnail_size
        USE_SIZE_FOR_HEIGHT = False
        '\\more code
    End Sub

    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        Try
            Dim imgContentType As String = UploadFile.PostedFile.ContentType

            If imgContentType.ToLower.StartsWith("image") Then
                Dim b As Drawing.Bitmap = Drawing.Image.FromStream(UploadFile.PostedFile.InputStream)
                Dim img_pk As Integer = 0
                Dim rowsaffected = dbAccess.SaveImageToDB(img_pk, BmpToBytes(b))
                If rowsaffected > 0 Then
                    createImageFromDBBytes(img_pk)				'***------> Here is where I am calling the sub and sending the variable
                Else
                    litException.Text = "<br /><p>Error Saving File!</p>"
                End If
            Else
                litException.Text = "<br /><p>The file is not an image</p>"
            End If
        Catch ex As Exception
            litException.Text = "<br /><p>" & ex.Message & "</p>"
        End Try
    End Sub
End Class

If I am again declaring the variables while passing them into the sub routine, how are the variables changing globally?

This is not a solution... In order for this to work the variables have to be passed into the sub routine. The subroutine that is passing the variable img_pk is being called by a subroutine from the same page class (Default) and not the ThumbFromID class.

So I ask again, How can I access the public variables that are located in the partial public class from other page classes?

Something to this logical effect (but for vb): The_Class.The_Variable

Edited by hrdfsique on Apr 13, 2009 06:40 PM

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hrdfsique

Member

31 Points

36 Posts

Re: Article 22603 Does not give a solution for this problem.

Apr 15, 2009 10:45 PM|LINK

I can't believe no one knows how to use partial public classes in vb!!!

Reply

asifchouhan

Participant

1637 Points

298 Posts

Re: Article 22603 Does not give a solution for this problem.

Apr 17, 2009 10:03 AM|LINK

Just have a look at this code

Here's a class that could be added to a project in VB 2005.

Public Class CombinedClass
   Private m_Property1 As String

   Public Sub New(ByVal Value As String)
      m_Property1 = Value
   End Sub

   Public Sub Method1()
      MessageBox.Show(m_Property1)
   End Sub

   Property Property1() As String
      Get
         Return m_Property1
      End Get
      Set(ByVal value As String)
         m_Property1 = value
      End Set
   End Property
End Class

This class can be called (for example, in the Click event code for a Button object) with the code:

Dim ClassInstance As New _
PartialClass("About Visual Basic Partial Classes")
ClassInstance.Method1()

I hope u are trying to do this

If you need more explanations go through this link

http://visualbasic.about.com/od/usingvbnet/a/partialclasses.htm

Regards

Asif

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Marked as answer by Shengqing Yang - MSFT on Apr 23, 2009 09:23 AM

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wRatte

Member

8 Points

8 Posts

Re: Article 22603 Does not give a solution for this problem.

Aug 05, 2009 03:48 PM|LINK

eh... the answer by asifchouhan is not really the answer to the question.

asifchouhan

Here's a class that could be added to a project in VB 2005...

he's actually looking for a solution to access public static/const variables among different web pages, not different classes. allow me to explain:

hrdfsique
In the default.aspx.vb code page I am trying to access the THUMBNAIL_SIZE variable. My logic tells me that all I would have to do is call it like this: ThumbFromID.THUMBNAIL_SIZE = "value", and indeed that works in C#.

hrdfsique, the key part here is not that you're trying to access the data from a different "partial" class... its that you're trying to access the data from a different web page's server side code. if you merely wanted to access data from a different partial class, you wouldn't even have posted this topic because you would've had no problems to do so (see your words that i'm quoting). unfortunately the fact that asp webpages have those partial classes is confusing, because in this case they won't act as you'd hope. you mentioned this works in C#? it doesn't. i tried to get it working in C# just now and got nowhere. like me, you'll have to store those const values in a normal class in your App_Code folder instead. here's a detailed explanation i got from this link:

http://www.justskins.com/forums/accessing-variables-of-another-class-85933.html

and the important parts that were mentioned: (especially the bolded text)

"ASP.Net Pages have 2 components which never meet... The client-side HTML and the server-side Class. They only SEEM to be connected...

...the server-side elements of these pages will never be able to see each other...

...On the client, the 2 pages (client-side HTML) exist in the same frameset...

...The only way to have these pages communicate is on the client-side, via
JavaScript. So, you will need to use JavaScript to access the HTML objects
in one page from the other page...

so that was the result i came across today (i had the same scenario as you did, only i tried to do it with C#). unless someone knows a wonderful way of getting the info, we're unfortunately limited to only the current web page's class and the App_Code classes.

only one life
it'll soon be past
only what's done for Christ will last

Accessing Variables in Partial Public Class RSS

6 replies

hrdfsique

Accessing Variables in Partial Public Class

hrdfsique

Re: Accessing Variables in Partial Public Class

asifchouhan

Re: Accessing Variables in Partial Public Class

hrdfsique

Article 22603 Does not give a solution for this problem.

hrdfsique

Re: Article 22603 Does not give a solution for this problem.

asifchouhan

Re: Article 22603 Does not give a solution for this problem.

wRatte

Re: Article 22603 Does not give a solution for this problem.

asifchouhan

hrdfsique

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