Creating classes in ASP.net that reference SQL server tables and return values
I am fairly new to ASP.net and want some expert help on best practice code design; I am designing in Visual Studio in express. I am giving an example of a part of my system design and would appreciate some help on a few design concepts. I have two power metering database tables set up, tblMETER which holds meter information and tblPOWER which holds 15 minute power meter readings. In my ASP.net program I want to use classes and objects to reference the many power meters.
This is what I think I should do, create a class called PowerMeter, set properties for NUMBER, DESCRIPTION, and DIVIDER. Now when I create an instance of the class for example PM06 (power meter 06), Firstly what is the best way to assign the property values to the new instance, Like this?
DIM PM06 as new PowerMeter
PM06.Number = “06”
PM06.Description = read the database referencing meter number 06
PM06.Divider = read the database referencing meter number 06
Secondly I want to display the total P_KW readings for the meter on a web page.
Do I create another property for the class and assign it the value such as
PM06.Reading = return calculated reading or is there some way of using a method within the class?
Providing some good points on getting a working system using best practices.
![Database Tables]()
This is what I think I should do, create a class called PowerMeter, set properties for NUMBER, DESCRIPTION, and DIVIDER. Now when I create an instance of the class for example PM06 (power meter 06), Firstly what is the best way to assign the property values to the new instance, Like this?
DIM PM06 as new PowerMeter
PM06.Number = “06”
PM06.Description = read the database referencing meter number 06
PM06.Divider = read the database referencing meter number 06
Secondly I want to display the total P_KW readings for the meter on a web page.
Do I create another property for the class and assign it the value such as
PM06.Reading = return calculated reading or is there some way of using a method within the class?
Providing some good points on getting a working system using best practices.
this link will help you create classes:
http://msdn.microsoft.com/en-us/library/ms973814.aspx
DIM PM06 as new PowerMeter
PM06.Number = “06”
PM06.Description = read the database referencing meter number 06
PM06.Divider = read the database referencing meter number 06
>>>>yes
display values to a web page....
add a label to your web form via design mode>drop a label on from toolbox on left had tab....
go back to source and enter this into the <script> tags
public sub page_load (object as sender, eventargs as e)
label1.text = PM06.Number
end sub
GlobalLevel,
Thanks for the reply. I have been doing some reading and come up with this. Use a constructor routine and pass the meter number on creation of the meter. Use that meter number to get the description and divider with a function inside the class code from the database.
I this something that would normally be done?
Thanks for the reply. I have been doing some reading and come up with this. Use a constructor routine and pass the meter number on creation of the meter. Use that meter number to get the description and divider with a function inside the class code from the database.
I this something that would normally be done?
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'Create the new power meter with its number
Dim PM06 As New PowerMeter("06")
End Sub
Imports System.Data.SqlClient
Public Class PowerMeter
Private mNumber As String
Private mDescription As String
Private mDivider As Integer
Private mDbConnection
Public Sub New(ByVal Value As String)
mNumber = Value
End Sub
ReadOnly Property number() As String
Get
Return mNumber
End Get
End Property
Property Description() As String
Get
Return mDescription
End Get
Set(ByVal value As String)
mDescription = value
End Set
End Property
Property Divider() As String
Get
Return mDivider
End Get
Set(ByVal value As String)
mDivider = value
End Set
End Property
End Class
looks good...r u using inline code or code behind?
for inline:
1)Page directive....
2) <@ Import xxxx
3) <scriptxxx>
methods
</script>
for inline:
1)Page directive....
2) <@ Import xxxx
3) <scriptxxx>
methods
</script>
Its a tricky question. It really depends on what level of abstraction you want to use and what type of objects you would return from that abstraction. Or maybe you're more interested in proper object creation than abstracting layers of communcication.
Anyway here's how I might go about this:
Dim pm1 = New PowerMeter()
Dim pm2 = New PowerMeter("2")
<see code>
Here's a code model you might be interrested in:
http://msdn.microsoft.com/en-us/library/aa581769.aspx
Its a pretty common sample from msdn. Instead of creating specific objects it prefers to abstract full data objects based off the db schema.
Anyway here's how I might go about this:
Dim pm1 = New PowerMeter()
Dim pm2 = New PowerMeter("2")
<see code>
Here's a code model you might be interrested in:
http://msdn.microsoft.com/en-us/library/aa581769.aspx
Its a pretty common sample from msdn. Instead of creating specific objects it prefers to abstract full data objects based off the db schema.
Imports Microsoft.VisualBasic
Imports System.Collections.Generic
Imports System.Data
Public Class PowerMeter
Private _number As String
Private _desc As String
Private _divider As String
Private _Readings As New List(Of PowerReadings)
Property Number() As String
Get
Return _number
End Get
Set(ByVal value As String)
_number = value
End Set
End Property
Property Description() As String
Get
Return _desc
End Get
Set(ByVal value As String)
_desc = value
End Set
End Property
Property Divider() As String
Get
Return _divider
End Get
Set(ByVal value As String)
_divider = value
End Set
End Property
ReadOnly Property Readings() As List(Of PowerReadings)
Get
Return _Readings
End Get
End Property
'Default Constructor
Public Sub New()
End Sub
''' <summary>
''' Gets PowerMeter by number Id
''' </summary>
''' <param name="num"></param>
''' <remarks></remarks>
Public Sub New(ByVal num As String)
GetMeterById(num)
End Sub
Public Function GetMeterById(ByVal num As String) As PowerMeter
For Each dRow As DataRow In PretendCallToDataAbstractionLayer(num).Rows
Me.Number = dRow("Number")
Me.Description = dRow("Description")
Me.Divider = dRow("Divider")
Me._Readings.Add(New PowerReadings(dRow("KDate"), dRow("KW")))
Next
Return Me
End Function
Private Function PretendCallToDataAbstractionLayer(ByVal num As String) As DataTable
Dim dTable As New DataTable("Meter")
dTable.Columns.Add("Number")
dTable.Columns.Add("Description")
dTable.Columns.Add("Divider")
dTable.Columns.Add("KDate", GetType(Date))
dTable.Columns.Add("KW")
dTable.Rows.Add("1", "SomeDesc", "SomeDivider", Date.Now, "150")
dTable.Rows.Add("1", "SomeDesc2", "SomeDivider2", Date.Now.AddDays(1), "200")
Return dTable
End Function
Class PowerReadings
Private _readingDate As Date
Private _kw As String
Property ReadingDate() As Date
Get
Return _readingDate
End Get
Set(ByVal value As Date)
_readingDate = value
End Set
End Property
Property KW() As String
Get
Return _kw
End Get
Set(ByVal value As String)
_kw = value
End Set
End Property
Public Sub New()
End Sub
Public Sub New(ByVal pDate As Date, ByVal p As String)
Me.ReadingDate = pDate
Me.KW = p
End Sub
End Class
End Class
ddayx10,
I am going over you example.
Thanks for your input., Actually I was looking at posting a seperate question on the correct use of datalink layers. At this stage it is the use of objects I want to get right. Its the use of methods I am struggling with at the moment, when to use and how to use. Ideally I want all objects in the ASP.net project created as much as possible from the database tables.
I am going over you example.
Thanks for your input., Actually I was looking at posting a seperate question on the correct use of datalink layers. At this stage it is the use of objects I want to get right. Its the use of methods I am struggling with at the moment, when to use and how to use. Ideally I want all objects in the ASP.net project created as much as possible from the database tables.
ddayx10,
Its going to take a while to get my head around it but I am sure the principle is there for what I am after. I am having trouible getting it to run though, just give me while.
Its going to take a while to get my head around it but I am sure the principle is there for what I am after. I am having trouible getting it to run though, just give me while.
Not a big deal but I made a mistake of sorts in the PowerReadings class. I would change that name to just PowerReading if it was me. Then when I looped through the list it would make more sense(its a small thing but it bugs me).
Ex:
for each p as PowerReadings in PowerMeter.PowerReadings
VS.
for each p as PowerReading in PowerMeter.PowerReadings
The latter makes contextual sense.
Ex:
for each p as PowerReadings in PowerMeter.PowerReadings
VS.
for each p as PowerReading in PowerMeter.PowerReadings
The latter makes contextual sense.