Like all the entity repositories in the site, the EventRepository contains members to do basic retrieval, inserting, and updating of EventInfo entities. There are a few custom retrieval methods to retrieve a list of events based on a specified date. They're described in the following table.

The EventRSVPRepository contains the basic repository members to perform CRUD operations against the entity data model. Here's a look at them:

The vCalendar Httphandler control sends an iCal card to the user. iCalendar is based on the vCalendar standard defined to exchange personal calendar information. Often used in group situations to coordinate meetings, free/busy services allow users to publish their schedules to others. The Beer House can use this to enable patrons to easily track what is happening in their favorite watering hole, which also meets the overall goals of distributing information about the Beer House. Fortunately distributing this type of information is very easy with a custom HttpHandler because it is just a formatted text document. For more information, see Request for Comment (RFC) 2445 (www.ietf.org/rfc/rfc2445.txt), which defines the format, and RFCs 2446 and 2447 (www.ietf.org/rfc/rfc2446.txt and www.ietf.org/rfc/rfc2447.txt), which define interoperability of the content between systems and free/busy services.

Several years ago I found a couple of useful projects on CodeProject.com (www.codeproject.com/KB/vb/vcalendar.aspx) to easily manage vCalendar and vCard documents. They work by adding values to the object graph that represents the data format, vCalendar in this case. Once the data has been added to the object calling the ToString method returns the properly formatted data as a string. This string can be returned however desired, for a web site this means setting the MIME type and adding the resulting string to the output stream. The MIME type for an iCalendar file is "text/calendar", which tells the browser which application should consume the resource being loaded. For most people this will be Outlook, but with the proliferation of mobile devices this could be almost anything, and because this is an open standard format it is nothing we need to be concerned with.

The handler's ProcessRequest method checks to make sure there is an EventId value passed in the QueryString. If not it calls the SendNoEventMessage to the browser, a nice message to the user letting them know what is wrong without throwing a hard exception that may not help the end user.

If Not IsNothing(Request.QueryString("EventId")) Then

BuildVCal()

Else

SendNoEventMessage()

End If

Private Sub SendNoEventMessage()
      'Instead of throwing an error, let the user know what they did wrong
in a graceful manner.CurrentContext
      CurrentContext.Response.ContentType = "text/HTML"
      CurrentContext.Response.Write(""P"Sorry, Please supply a valid EventId."/P"")
      CurrentContext.Response.Flush()
      CurrentContext.Response.End()
      Exit Sub
End Sub

If an EventId value is present the BuildVCal method is called. It again does a quick test to make sure the EventId value is positive, if not the SendNoEventMessage is called. Next the event is retrieved from the database and the values are passed to a vCalendar object. The way the vCalendar works is it can contain multiple vEvent and vAlarm objects, both defined within the vCalendar class. The handler is concerned with just a single event, so only one vEvent object is created. The Description, Location, and URL properties are set first. Then the event date and times are set.

Setting the event date and time takes a little extra effort because the event start and end times are defined in separate database fields from the start and end dates. A new composite DateTime value must be created for each. The logic has to be aware of empty end dates and times. The time fields are stored as a string, so I used a regular expression to parse the Hour, Minute and AM/PM values. I chose to keep this pretty simple, assuming the data should be formatted in the format according to the MaskEditExtender I will talk about in the Solution section.

Be aware the EventEndDate value is a Nullable type and therefore you need to convert this to a real DateTime class using the GetValueOrDefault method. If the EventEndDate is null, then the EventDate is assumed to be the EventEndDate. This will be the case for most events because they should be more like appointments that last a few minutes or a few hours.

Null values are a common problem for programmers in any language and platform. Null dates in particular seem to be a common issue developers experience when they start dealing with null values. The .NET framework provides three things that can help the situation: nullable types in C# and VB.NET, a coalesce operator in C# (int x = y ?? 5), and the inline If statement in VB.NET (Dim x as integer = If(y, 5)).

In .NET value types can be declared as a nullable type, which ultimately gets compiled to the Nullable(of T) structure. This structure has four members: Value, HasValue, GetValueOrDefault and GetValueOrDefault(defaultValue as T).

When the Entity Data Model Wizard encounters a field that allows null values, it creates the corresponding property as a nullable value:

Public Property EventEndDate() As Global.System.Nullable(Of Date)
            Get
                Return Me._EventEndDate
            End Get
            Set(ByVal value As Global.System.Nullable(Of Date))
                Me.OnEventEndDateChanging(value)
                Me.ReportPropertyChanging("EventEndDate")
                Me._EventEndDate = Global.System.Data.Objects.DataClasses
.StructuralObject.SetValidValue(value)
                Me.ReportPropertyChanged("EventEndDate")
                Me.OnEventEndDateChanged()
            End Set
End Property

In addition to using the GetValueOrDefault member I have also found the use of the Coalesce functionality to be very valuable. In C# this is represented by ??; here's an example:

int? x = null;
int y = x ?? 5;

VB.NET uses a hybrid of the if statement to manage coalescing:

Dim x as Integer? = Nothing
Dim y as Integer = if(x, 5)

This is why the following line is used to set the actual event end date:

Dim dtEnd As DateTime = If(lEventInfo.EventEndDate, lEventInfo.EventDate)
Private Sub BuildVCal()

      Using lEventrpt As New EventRepository

         Dim lEventId As Integer = CInt(Request.QueryString("EventId"))

         If lEventId <= 0 Then
            SendNoEventMessage()
         End If

         Dim lEventInfo As EventInfo = lEventrpt.GetEventInfoById(lEventId)

         If Not IsNothing(lEventInfo) Then

            Dim lvCal As New vCalendar
            Dim lEvent As New vCalendar.vEvent

            lEvent.Description = lEventInfo.EventTitle

lEvent.Location = lEventInfo.EventLocation
            lEvent.URL = String.Format("{0}?eventid={1}", _
                        Path.Combine(Helpers.WebRoot, "ShowEvent.aspx"), _
                        lEventId)
            lEvent.Summary = lEventInfo.EventDesc

            Dim rgTime As New Regex("^(d{2}):(d{2}):(d{2}) (PM|AM)$")

            Dim mHour As Integer = 0
            Dim mMinute As Integer = 0

            For Each m As Match In rgTime.Matches(lEventInfo.EventTime)

               If m.Groups.Count > 3 Then

                  If m.Groups(4).Value = "PM" Then
                     mHour = 12 + m.Groups(1).Value
                  Else
                     mHour = m.Groups(1).Value
                  End If

                  mMinute = m.Groups(2).Value

               End If

            Next

            lEvent.DTStart = New Date(lEventInfo.EventDate.Year,
lEventInfo.EventDate.Month, lEventInfo.EventDate.Day, _
                                    mHour, mMinute, 0)

            mHour = 0
            mMinute = 0

            For Each m As Match In rgTime.Matches(lEventInfo.EndTime)

               If m.Groups.Count > 3 Then

                  If m.Groups(4).Value = "PM" Then
                     mHour = 12 + m.Groups(1).Value
                  Else
                     mHour = m.Groups(1).Value
                  End If

                  mMinute = m.Groups(2).Value

               End If

            Next

            'EventEndDate is a Nullable type, so we need to convert it
to a hard date and time.
            Dim dtEnd As DateTime = If(lEventInfo.EventEndDate,
lEventInfo.EventDate)

            If mHour > 0 Then

lEvent.DTEnd = New Date(dtEnd.Year, dtEnd.Month,
dtEnd.Day, mHour, mMinute, 0)
            End If

            lvCal.Events.Add(lEvent)

            CurrentContext.Response.ContentType = "text/calendar"
            CurrentContext.Response.ContentEncoding = Text.Encoding.UTF8
            CurrentContext.Response.Write(lvCal.ToString)
            CurrentContext.Response.Flush()
            CurrentContext.Response.End()

         Else

            SendNoEventMessage()

         End If

      End Using

End Sub

Just like the other HttpHandlers I have introduced in this version of the book, the custom handler needs to be registered in the web.config file and associated with a URL. For the iCalendar file type the standard extension is .ics, so we will stick with that standard and associate any request for an .ics file with the custom handler:

<add verb="*" path="*.ics" validate="false" type="TheBeerHouse.vCalHandler,
TBHBLL, Version=3.5.0.1, Culture=neutral, PublicKeyToken=null"/>

With these pieces in place, iCalendar files can be streamed dynamically from the Beer House's web site with the click of a hyperlink and added to the patron's personal schedule Figure 10-4.

Figure 10.4. Figure 10-4

In addition to the basic CRUD methods that follow the same patterns used in previous repositories there are three custom functions in the EventRepository to return a list of events based on specified dates.

The GetDaysEvents function runs a LINQ to Object query over the results of the GetActiveEvents function to return just a list of events for the specified day. The GetTodaysEvents function returns a list of events for the current date by passing the current date to the GetDaysEvents function. The results of the GetActiveEvents are cached (assuming that is enabled), so these methods should be very fast because they are querying against an in-memory list.

Public Function GetTodaysEvents() As List(Of EventInfo)

Return GetDaysEvents(Today)

End Function

Public Function GetDaysEvents(ByVal vDate As DateTime) As List(Of EventInfo)

Return (From lEventInfo In GetActiveEvents() Where lEventInfo.EventDate =
vDate).ToList

End Function

The GetUpcomingEvents function retrieves a list of events occurring on the current day and after. Because it is a LINQ statement, the EventDate property can be compared against the Today value using the "= operator. Notice I am still using the Active=True filter. I tend to do this because you will very rarely work with inactive records in the database; remember the default GetEvents or get a list method in each repository does not apply this filter, so retrieving and working with inactive data can always be done.

Public Function GetUpcomingEvents() As List(Of EventInfo)

         Dim key As String = CacheKey & "_Upcoming_n" & Today

         If EnableCaching AndAlso Not IsNothing(Cache(key)) Then
            Return CType(Cache(key), List(Of EventInfo))
         End If

Dim lEvents As List(Of EventInfo)
         Eventctx.EventInfos.MergeOption = Objects.MergeOption.NoTracking

         lEvents = (From lEventInfo In Eventctx.EventInfos _
               Where lEventInfo.EventDate "= Today _
               And lEventInfo.Active = True).ToList()

         If EnableCaching Then
            CacheData(key, lEvents)
         End If

         Return lEvents

End Function

Outside the standard repository methods, the EventRSVPRepository has a the GetEventRSVPByEventId method, which returns a list of EventRSVP entities for the specified event.

Public Function GetEventRSVPByEventId(ByVal EventId As Integer) As List(Of
EventRSVP)

Dim key As String = CacheKey & "_List_By_EventId_" & EventId

If EnableCaching AndAlso Not IsNothing(Cache(key)) Then
            Return CType(Cache(key), List(Of EventRSVP))
End If

Dim lEventRSVPs As List(Of EventRSVP)
Eventctx.EventRSVPs.MergeOption = Objects.MergeOption.NoTracking

lEventRSVPs = (From lEventRSVP In Eventctx.EventRSVPs.Include("EventInfo") _
                           Where lEventRSVP.Active = True And
lEventRSVP.EventInfo.EventId = EventId).ToList()

If EnableCaching Then
            CacheData(key, lEventRSVPs)
End If

Return lEventRSVPs

End Function

This page, located under the ~/Admin folder, allows the administrator to view a list of events, add a new event, edit and event, and delete an event. The page is composed of a ListView surrounded by an UpdatePanel to list the events. Each event list the event title and the date in the first column. The ListView also contains the familiar Pencil icon that is a hyper link to edit the event and the delete icon is the familiar trash can icon. The RSVP column contains a hot linked image that opens the ManageEventRSVPs.aspx page, filtered for the specified event. Figure 10-5 is a screenshot of the page.

Figure 10.5. Figure 10-5

The AddEditEvent.aspx page provides the visual representation to manage the information about an event. The page uses some of the ASP.NET AJAX control toolkit controls and extenders to add to the user experiences of the page. Primarily it uses the CalendarExtender and the MaskedEditExtender. The use of these controls to help users enter valid dates was covered in Chapter 4. But for a quick review, the CalendarExtender is used to display a Calendar control when the user clicks on the calendar icon to the right of the corresponding TextBox. The MaskEditExtender uses a mask, which looks somewhat like a regular expression, to format a date. For a date the Mask property is set to "99/99/9999" and the MaskType is set to Date.

The Allow Registration checkbox (near the bottom of Figure 10-6) is important to note simply because checking this control will enable users to RSVP for the event. If this is left unchecked, then registration is suppressed for visitors. Because some events need to have a projected attendance ahead of time for planning purposes, while others to do not, keep this in mind when defining an event.

Figure 10.6. Figure 10-6

The BrowseEvents.aspx page uses a Calendar control and a ListView to display information about the event calendar. The Calendar is used to display highlighted days when events are scheduled. The ListView displays a list of upcoming events, but when a date is selected on the Calendar control a list of events for that date is displayed. The list displays the event title, date, start time, and location along with the title and a More Information link to the ShowEvent.aspx page for the event. The actual business area of the page is wrapped in an UpdatePanel to make filtering for specific days pretty seamless for the user's experience.

The Calendar control is styled so the current day and days with events stand out from other days, which helps users know when events are scheduled:

<asp:Calendar ID="objCalendar" runat="server" BorderColor="Black"
BorderStyle="Solid" BorderWidth="1px">
<TodayDayStyle CssClass="TodayDayStyle"></TodayDayStyle>
<DayStyle CssClass="DayStyle"></DayStyle>
<DayHeaderStyle CssClass="DayHeaderStyle"></DayHeaderStyle>

<TitleStyle CssClass="TitleStyle"></TitleStyle>
<OtherMonthDayStyle CssClass="OtherMonthDayStyle"></OtherMonthDayStyle>
</asp:Calendar>

Figure 10-7 shows the page in action.

Figure 10.7. Figure 10-7

Protected Sub objCalendar_DayRender(ByVal sender As Object, ByVal e
As System.Web.UI.WebControls.DayRenderEventArgs) Handles objCalendar.DayRender

      Using lEventrpt As New EventRepository

         Dim lEventList As List(Of EventInfo) =
lEventrpt.GetDaysEvents(e.Day.Date.ToShortDateString())
         If lEventList.Count > 0 Then

Dim EventStyle As New Style()
            With EventStyle

               .BackColor = System.Drawing.Color.DarkRed
               .Font.Bold = True
               .ForeColor = Drawing.Color.White

            End With

            e.Day.IsSelectable = True
            e.Cell.ApplyStyle(EventStyle)

         Else

            e.Day.IsSelectable = False

         End If

      End Using

End Sub

Protected Sub objCalendar_SelectionChanged(ByVal sender As Object, ByVal e
As System.EventArgs) Handles objCalendar.SelectionChanged
        BindDaysEvents(objCalendar.SelectedDate)
End Sub

Protected Sub objCalendar_VisibleMonthChanged(ByVal sender As Object, ByVal e
As System.Web.UI.WebControls.MonthChangedEventArgs) Handles
objCalendar.VisibleMonthChanged
        BindData()
End Sub

Private Sub BindDaysEvents(ByVal vDate As DateTime)

        Using lEventrpt As New EventRepository

Dim lEventList As List(Of EventInfo) =
lEventrpt.GetDaysEvents(objCalendar.SelectedDate)

            If lEventList.Count > 0 Then

                lvEvents.DataSource = lEventList
                lvEvents.DataBind()

                Dim pagerBottom As DataPager = lvEvents.FindControl("pagerBottom")

                If Not IsNothing(pagerBottom) Then
                    If lEventList.Count "= pagerBottom.PageSize Then
                        pagerBottom.Visible = False
                    Else
                        pagerBottom.Visible = True
                    End If
                End If

            Else

                lvEvents.Items.Clear()

            End If

        End Using

End Sub

MakeEventRSVP.aspx Page

If an event has the AllowRegisration flag set to true the user can RSVP for the event. A link to do so is available on the event's ShowEvent.aspx page and loads the MakeEventRSVP.aspx page. This page operates almost exactly like an entity Add/Edit page in the site's Admin section. The main difference is the use of the MultiView. Initially the registration form is displayed, but once the RSVP has been successfully submitted a confirmation view is displayed to the user.

<asp:MultiView runat="server" ID="mvRegistration">
<asp:View runat="server" ID="vRegister">
'Registration Form
</asp:View>
<asp:View runat="server" ID="vConfirmation">
'Confirmation Form
</asp:View>
</asp:MultiView>

Figure 10-8 shows the registration and confirmation views.

Figure 10.8. Figure 10-8