Gregory Rubinstein

OOP Primer

2011-03-10T16:37:00Z

Definition:

Object-oriented programming (OOP) is a programming paradigm that uses "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction, encapsulation, modularity, polymorphism, and inheritance.

Example:

Assume that we want to keep track of all our contacts. In order to do that, we'll have to describe a contact object as a class that has certain properties (qualities) and methods (behaviors). For example, if we want to track each contact's name, phone number and birthday information, we should create a property for each of those attributes in our contact class (see below) and initialize them prior to instantiating the contact object:

Public Class contact

Private pFirstName As String
Private pLastName As String
Private pPhone As String
Private pDateOfBirth As DateTime
    Public Property FirstName() As String
        Get
            Return pFirstName
        End Get
        Set(ByVal value As String)
            pFirstName = value
        End Set
    End Property

    Public Property LastName() As String
        Get
            Return pLastName
        End Get
        Set(ByVal value As String)
            pLastName = value
        End Set
    End Property

    Public Property PhoneNumber() As String
        Get
            Return pPhone
        End Get
        Set(ByVal value As String)
            pPhone = value
        End Set
    End Property

    Public Property DateOfBirth() As DateTime
        Get
            Return pDateOfBirth
        End Get
        Set(ByVal value As DateTime)
            pDateOfBirth = value
        End Set
    End Property

Public Sub New()

  LastName = String.Empty
  FirstName = String.Empty
  PhoneNumber = String.Empty
  DateOfBirth = DateTime.MinValue

End Sub

End Class

Now that we have defined the different properties of our contact object, we can begin describing the different methods/functions that we will use with our contact object. One thing that we'll want to be able to do is to look up information of a specific contact. In order to do that, we'll have to add an additional property to our contact object that will uniquely identify that specific contact. We'll name that property ContactId and make it an Integer and initialize it to 0 in the constructor:

    Private pContactId As Integer
    Public Property ContactId() As Integer
        Get
            Return pContactId
        End Get
        Set(ByVal value As Integer)
            pContactId = value
        End Set
    End Property
Public Sub New()

  LastName = String.Empty
  FirstName = String.Empty
  PhoneNumber = String.Empty
  DateOfBirth = DateTime.MinValue
ContactId = 0

End Sub

Public Function GetContactInfo(ByVal ContactId As Integer) As contact

'Code that retrieves the information and then returns the contact object goes here

End Function

Happy Coding!

Passing Parameter to Crystal Report

2008-08-14T16:17:00Z

Recently, I was developing a pretty sophisticated Crystal Report that included multiple sub-reports and used multiple stored procedures as data sources. All of those stored procedures accepted the same parameter, which made my life a little easier, since I only had to deal with one parameter that I needed to pass to my Crystal Report.

In order for all sub-reports to be able to recognize the parameter, which I am passing to the main report, I had to link all of my sub-reports to the main report using that parameter.

In order to link a sub-report to the main report, the following actions should be performed:

To link a subreport to the data in the primary report

If you are creating a new subreport or importing an existing report as a subreport, from the Insert menu, click Subreport. Choose or create a report and click the Link tab.
- or -

If you have already placed a subreport in the primary report, but did not create a link at setup, navigate to the Subreport Links dialog box by choosing Subreport Links from the Edit menu.

The Subreport Links dialog box appears.
Choose the subreport you want to link from the For subreport list (if it is not already selected).
Select the field you want used as a link field in the primary (containing) report from the Available Fields list.
Click the > arrow.
The field is added to the "Field(s) to link to" list box, and is now selected as a link field.
Repeat steps 3 and 4 for each additional link, as desired.
Use the Field link section (which will only appear if you have selected a link field) to set up the link for each link field:
- Select the field you want linked to the primary report from the "Subreport parameter field to use."
- Select the "Select data in subreport based on field" check box on and select a field from the adjacent drop-down list to organize the subreport data based on a specific field (this is the quick equivalent of using the Select Expert). If nothing is specified here, the subreport will adopt the organization of the primary report.
Click OK.

When you run the report, the program will coordinate the data in the primary report with the data in the subreport.

Below is the code that I used to pass my parameter to the Crystal Report and then display it in PDF format to the end-user:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

GenerateReport(Session("EmpId"))

End Sub

Private Sub GenerateReport(ByVal EmpId As Integer)

Dim theReport As New ReportDocument
theReport.FileName = "C:\myProject\Reports\myReport.rpt"
theReport.SetDatabaseLogon(PCON.APP.UserName, PCON.APP.Pass, PCON.APP.db_Server, PCON.APP.dbName)

'Set the required parameter for Crystal Report
theReport.SetParameterValue("@Id", EmpId)

'Now, present report in PDF format
theReport.ExportToHttpResponse ( ExportFormatType.PortableDocFormat, Response, False, "ExportedReport")

End Sub

Crystal Reports with ASP.NET

2008-05-10T02:28:00Z

When it comes to developing a report for an ASP.NET application, one might find that there is very little information available on how it's done using Crystal Reports.

Visual Studio 2003 comes with a built-in version of Crystal Reports (CR 9). Using that built-in version of Crystal Reports might save you some money, since it's a part of VS 2003, however, from the Crystal Reports design prospective it is much more convenient to use a stand-alone version of Crystal Reports.

The latest version of Crystal Reports at the time of writing this post is Crystal Reports XI, which provides some new features, not available in previous versions (see the www.businessobjects.com website for more info), so in my last development I used that version of Crystal Reports.

In order for the report to display as a webpage, VS 2003 provides CrystalReportViewer control. This is how it works:

Instantiate the DataSet object
Dim ds As New DataSet ds = GetDataForReport() 'some method that retrieves data for the report Instantiate the ReportDocument object: Dim rpt As New ReportDocument 'set the ReportObject as the report you want to display rpt = New CrystalReport1 'Define the datasource of your report rpt.SetDataSource(ds) 'define your report as a reportsource for the crystalreportviewer CrystalReportViewer1.ReportSource = rpt
Below is C# version of this code:
DataSet ds = new DataSet(); ReportDocument rpt = new ReportDocument(); rpt = new CrystalReport1(); rpt.SetDataSource(ds); CrystalReportViewer1.ReportSource = rpt;

In order for this code to work, the following namespaces must be imported/used:

CrystalDecisions.CrystalReports.Engine
CrystalDecisions.Shared
CrystalDecisions.Web.Design

The following namespaces should be used only if you are planning to convert the report into a PDF, Word, or Excel format.

CrystalDecisions.Shared.ExportDestinationType
CrystalDecisions.Shared.ExportFormatType
CrystalDecisions.Shared.ExportDestinationOptions

Converting ASP.NET to PDF

2008-05-10T02:21:00Z

I probably wouldn't be wrong if I said that most developers every now and then are tasked to present specific data contained in a webpage as a PDF document. There are two ways to do it:

using the functionality of CrystalReportViewer's toolbar - this toolbar provides a button, which does exactly that. However, to use this approach you would have to actually display the crystal report on the page.

programmatically convert the Crystal Report object into a PDF document using the Crystal Reports API

Below is the code for the second approach:

Dim report As CrystalReport1 = New CrystalReport1
SqlDataAdapter1.Fill(DataSet11)
report.SetDataSource(DataSet11)
report.ExportToHttpResponse (ExportFormatType.PortableDocFormat, Response, False, "ExportedReport")

Remaining Characters Counter

2008-04-11T02:06:00Z

Recently I was developing a webform (asp.net) where the user could submit his feedback, and one of the requirements was that the user should not enter more than a set number of characters in his message, so I thought it would be real nice for the end user to know how many more characters he still can type until the maximum limit is reached.

In order to allow that functionality, I created a asp.net multiline textbox for text input and an html readonly text field (for displaying number of characters until the maximum).

Then, I created a Javascript function and called it every time the contents of the multiline textbox changed (onKeyUp and onChange events).

Below is the code:

<html>
<head>

<script language="JavaScript">

function CountChars(text,long)

{
   var maxlength = new Number(long);
   var myLength = text.value.length;
   document.forms[0].Counter.value = maxlength - myLength;
   if (myLength > maxlength) {
      text.value = text.value.substring(0,maxlength);
   }
}

</script>

</head>
<body>

<form id="Form1" runat="server">

<asp:Textbox mode="multiline" id="txtMessage" runat="server" /><br />

<input type="text" name="Counter" readonly="readonly" />

</form>

</body>
</html>

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Util.SetTextBoxProperties(txtMessage, True)
End Sub

Below is the SetTextBoxProperties method, which actually did the work:

Public Sub SetTextBoxProperties(ByVal txt As TextBox)
    txt.Attributes.Add("onKeyUp", "CountChars(this," & txt.MaxLength & ")")
    txt.Attributes.Add("onChange", "CountChars(this," & txt.MaxLength & ")")
End Sub

Active Control Marker

2008-04-10T04:07:00Z

Today, while working on my project, I recalled that some of the data entry pages in my project have a lot of textboxes, which may confuse the end-user once he starts entering information. My idea was to make the textbox that has focus visually different from the rest, so I came up with the following code snippet, that does the actual work:

Public Sub ShowActiveTextbox(ByVal txt As TextBox)

txt.Attributes.Add("onfocus", "this.className='class1'")
txt.Attributes.Add("onblur", "this.className='class2'")

End Sub

This code would work just fine if I had only one or two Textboxes on my page. However, some of the pages may contain a dozen of those textboxes, so I came up with another useful method:

Public Sub ShowActiveTextbox(ByVal col As ControlCollection)

For Each Ctl As Control In col

If Ctl.GetType().Name = "Textbox" Then

Call ShowActiveTextbox(Ctl)

Else

'Handle TextBoxes contained in container controls, such as panel
If ctl.Controls.Count > 0 Then

Call ShowActiveTextBox(ctl.Controls)

End If

Next
End Sub

Now we have a method that will handle any number of controls on a specific page and will apply the onFocus and onBlur event handlers to all Textboxes on that page.