I've created a function in my vb class file that creates dynamic tables. I'm planning to use this to create tables dependent on a button being clicked. The function references a placeholder in my aspx page but I'm getting "placeHolder1 is not declared".
How can I access controls on my form from my class file?
Thanks
Class file snippet as follows:
Public Shared Function CreateTable() As Table
'handle either total or breakdown
Select Case format
Case "breakdown"
placePayDetails.Controls.Clear()
Dim tblPayDetails As Table = New Table()
placePayDetails.Controls.Add(tblPayDetails)
etc
According to your updated version of the question, your CreateTable function needs to receive a placePayDetails (presumably of type ContentPlaceHolder) as parameter.
The page calling this function needs to have this place holder defined somewhere in the markup.
Example:
Public Shared Function CreateTable(byVal placePayDetails as ContentPlaceHolder) As Table
'handle either total or breakdown
Select Case format
Case "breakdown"
placePayDetails.Controls.Clear()
Dim tblPayDetails As Table = New Table()
placePayDetails.Controls.Add(tblPayDetails)
the class file has no concept of your page. if you have a function in your class where you want the results of that function to return to the page, on the aspx backend have the function's results returned to as string and then set the contents
Dim tblPayDetails As Table = DoSomething()
placePayDetails.Controls.Add(tblPayDetails)
Related
I’m building an Access database with classes e.g clsOrder, clsCustomer etc which manage the interface with tables. These classes create instances of forms when displaying their data. I found that once the execution of code was within one of these forms I couldn’t refer to the parent object that created it (so is there a better way of doing this? would be part of my question).
To deal with this I’m using a scripting dictionary to store instances of classes with a key using the ID of the class and a unique identifier for the class (e.g Order-3265). I then store a reference to the owner object in the form itself.
So when an object is created and its ID is known it puts a pointer to itself in the dictionary and gives that pointer to its form (hope that’s clear enough).
This then allows the form to interact with its owner class.
I’m using another class clsManager to do the adding of items to the Dictionary or retrieval or removal (with destruction).
Examples of classes - seriously cut down..
clsManager:
Public WorkingObjects As New Scripting.Dictionary
Public Function AddWorkingObject(key As String, ObjectType As Object) As Boolean
If Me.WorkingObjects.Exists(key) Then
Me.WorkingObjects.Remove key
Me.WorkingObjects.Add key, ObjectType
Else
Me.WorkingObjects.Add key, ObjectType
End If
End Function
Public Function GetWorkingObject(key As String) As Object
If Me.WorkingObjects.Exists(key) Then
Set GetWorkingObject = Me.WorkingObjects(key)
Else
Set GetWorkingObject = Nothing
End If
End Function
Public Function DestroyObject(obj As Object) As Boolean
Dim key As String
If Not obj Is Nothing Then
key = obj.DictionaryKey
If Me.WorkingObjects.Exists(key) Then
Me.WorkingObjects.Remove (key)
Set obj = Nothing
If obj Is Nothing Then
Debug.Print key & " destroyed"
Else
Debug.Print obj.DictionaryKey & " NOT destroyed"
End If
End If
Set obj = Nothing
End If
End Function
clsQuote:
Option Compare Database
Option Explicit
'use a form using an instance of this class to control manipulation of Quote records
'Loading and saving set default values if a null value is detected
Private Const scTABLE As String = "tblQuote"
Private intID As Long 'unique identifier
Private intCustomerID As Long
Private intSiteID As Long
Private rsQuoteTotalValues As DAO.Recordset
Private oCustomer As clsCustomer
Const ObjectType = "Quote-"
Private oEditForm As Form_frmQuote
Property Get EditForm() As Form_frmQuote
Set EditForm = oEditForm
End Property
Property Get ID() As Long
ID = intID
End Property
Property Let ID(QuoteID As Long)
intID = QuoteID
Me.EditForm.ID = QuoteID
End Property
Property Get Customer() As clsCustomer
Set Customer = oCustomer
End Property
Property Let CustomerID(ID As Long)
intCustomerID = ID
oCustomer.Load (ID)
EditForm.SiteID.RowSource = oCustomer.AddressSQL
EditForm.SiteID.Requery
EditForm.ContactID.RowSource = oCustomer.ContactsSQL
EditForm.ContactID.Requery
EditForm.CustomerID = ID
End Property
Property Get DictionaryKey() As String
DictionaryKey = ObjectType & CStr(Me.ID)
End Property
'END PROPERTIES//////////////////////////////////
Public Sub DisplayForm(Visibility As Boolean)
With Me.EditForm
.Visible = False
.subFrmQuoteSectionsSummary.SourceObject = ""
If Visibility = True Then
...some stuff...
.Visible = True
End If
End With
End Sub
Public Function Load(ID As Long) As Boolean
'On Error GoTo HandleError
Dim RS As DAO.Recordset
Dim sQry As String
Load = False
If Nz(ID, 0) <> 0 Then
sQry = "SELECT * FROM " & scTABLE & " WHERE ([ID]=" & ID & ");"
Set RS = Manager.DB().OpenRecordset(sQry, dbOpenForwardOnly)
With RS
If .RecordCount = 0 Then
MsgBox "Cannot find Quote with ID = " & ID, vbCritical
GoTo Done
End If
Me.ID = Nz(!ID, 0)
Me.CustomerID = Nz(!CustomerID, 0)
Manager.AddWorkingObject Me.DictionaryKey, Me
Me.EditForm.SetOwnerObject (Me.DictionaryKey)
.Close
End With
Set RS = Nothing
Load = True
End If
Done:
Exit Function
HandleError:
MsgBox "Error in Customer Load: " & vbCrLf & Err.Description, vbCritical
Resume Done
End Function
Private Sub Class_Initialize()
Debug.Print "Quote class initialized"
Set oCustomer = New clsCustomer
Set oEditForm = New Form_frmQuote
Me.ID = 0
Set oQuoteTidier = New clsClassTidier
Me.DisplayForm (False)
End Sub
Private Sub Class_Terminate()
Set oCustomer = Nothing
Set oEditForm = Nothing
Debug.Print "Quote class terminated"
End Sub
From the EditForm:
Option Compare Database
Option Explicit
'necessary for the object to have a reference to its owner in this manner to prevent circular reference
Private OwnerObject As clsQuote
Public Function SetOwnerObject(OwnerKey As String) As Boolean
SetOwnerObject = False
Set OwnerObject = Manager.GetWorkingObject(OwnerKey)
SetOwnerObject = True
End Function
Private Sub cmdClose_Click()
OwnerObject.EditForm.Visible = False
Manager.DestroyObject OwnerObject
DoCmd.Close acForm, Me.Name
End Sub
Each business object class (like ClsOrder) has an editForm instance which is loaded and hidden until required and a up to 3 DAO Recordsets that it keeps open.
I think all references to the business objects that are interrelated are pointers to the objects in the dictionary.
My problem is error 3035 exceeding system resources. I’ve checked objects are destroyed when not in use but repeatedly opening and closing objects gets me to error 3035.
So the question is- am I just asking Access to do stuff it can’t or would better programming fix it?
I see ZERO reasons to write all that code. Why not let a form handle all of this? Remember, each form is in fact a "class" instance. You can even launch multiple copies of a single form, each with their own code, own data and each instance of the SAME form can operate 100% independent of other working copies of that same form.
If you attempting to look at this problem and wanting to have a class object for a form, then just use the form object - that's what it does for you!
I see zero benefits from writing all that code. While .net has the dataset manager and system (and now the very similar entity framework, this is MUCH done since .net does not have data bound forms.
In Access, each form is in fact a class object. And that includes any public sub or function for that form (so functions become methods of that form, and public vars become properties of that form). In addition to the bound form having a truckload events, these events work as actions against any data editing. So, unlike most systems, you have "on change" event, before update event, after update event. So, by simply adoptiing a bound form, then you get:
A class object is automatic created for you.
You can have multiple instances of that class, and hence multiple instances of that same form open at the same time.
You get all of those data events that can be used for verifiction of data input (or have the user not save the record until such time your critera is met.
You have full use of all data columns, even if controls are NOT placed on the form bound to those columns. So, you even get intel-sense for all of the data columns - that is you map.
I am not aware that there is some big huge circular reference problem here. This is like stubbing your toe, but then going to the doctor for some huge open heart by-pass operation. So to go on some huge massive coding spree, and chew up huge amounts of developer dollars for some "rare" issue of some kind of rare and un-seen circular reference issue is essentially a huge wild goose chase that will only have you chewing up huge amounts of developer code and time when NONE is required at all.
I mean, if you have say 3 instances of the SAME form open? Then how does the code know and refernce what insance of that form? Well, the EXACT same approac used in typical OO programming can and should be used here. That approach means you don't HARD CODE the forms! name or referances in code EVER. You never want to do this.
So, if you are in a sub form, and need to referacne say data or controls in the parent form?
You could do this:
strLastName = forms!frmCustomer!LastName
In above, we have hard coded the forms name. You don't want to do that.
In that subform, the correct way to write this code is:
strLastName = me.Parent.form!LastName
Now, note how the above referances the parent form. So, that code will work EVEN if we have 3 copies of the frmCustomer active at the same time. You can full refernce ANYTHING in a form by its object "instance". So, in JavaScrip, or c#, you often see "this.SomProperty" as a refeance to that object.
In access, you can do the same thing, and use "me". Or me.Parent.From to reference the parent form. So, as a general approach here, you should NEVER have to hard code forms reference. If you take this approach, then all issues of circular referencing will not only be eliminated, but then you are using a classic and traditional approach to object programming, and object referencing. While Access is not full OO, it certainly follows a lot of OO design concepts, and how forms work in Access are most certainly instances of a object.
Attempting to write truckloads of code when the forms object model already exists as a "single" class object instance of that form makes no sense, and is not required, and the road you going down will likely hamper and reduce your abilities to deal with the fantastic instance of that form you already have.
As noted, the form already has the dictionaly and columns attached, and Access EVEN generates the members for your automatic. The result is you can reference any column of the table that the form is bound to with
me.LastName
me!LastName
While the above two formats are allowed, the first (me + dot + column name) is in fact a member of the forms class. You will find that if you use code to set the forms data source, then often these members are NOT generated for you, and thus you have to use the ! (bang) to reference columns from the table for that form.
So, I don't grasp while you attempting all that extra code when the form has all of the abilities you are asking for in a class object.
I have been building various web based programs and things for a while, but am quite new to .NET and doing things "properly." As I am completely self taught, with help from sites like this and so on, my understanding of fundamentals is limited.
So, I have a series of functions which return data that I want depending on parameters put in, this is very basic stuff, and obviously all works. However, I am trying to make it easier to call these functions by using Classes.
So, say I have a function which returns a populated DropDownList converted to an HTML string
Function GetList(ListRequired as String) as String
' Do stuff to return a dropdownlist whos contend is determined by `ListRequired`, converted to an HTML string
End Function
In this example, it works fine, but to use it I must know what to enter for "ListRequired" to get what I want.
So, let's say, the options for the ListRequired para are "mastercategory", "brandlist", "priceranges" to return a different set of lists - each option would send the code off the retrieve information from a database and return accordingly.
Suppose I want a third party developer to be able to call this function with the most basic amount of "instruction" required, and not even have to tell him the list of available ListRequired by making it available as a Class.
Public Class DropDownLists
Public Property MasterCategory
Public Property BrandList
Sub New()
Me.MasterCategory = HTMLControls.RenderSearchFilters("mastercategory")
Me.BrandList = HTMLControls.RenderSearchFilters("brandList")
End Sub
End Class
A developer can then call this from Visual Studio/VWD etc very simply:
Dim dd As New DropDownLists
Dim list1Html as String = dd.MasterCategory
Dim list2Html as String = dd.BrandList
Because VWD etc creates all the handy helpers and displays which properties the Class exposes, it is very easy to use this code without have to constantly refer to a manual.
However... when creating a new instance of the Class:
Dim dd As New DropDownLists
This will cause the server to process all the functions within the class which create the Properties, which would be desperately inefficient if there are lots of properties.
So I have tried using my own interpretation of the logic and written this:
Public Class DropDownLists
Shared Property Master
Shared Property Brand
Sub New()
End Sub
Public Class MasterCategory
Sub New()
DropDownLists.Master = HTMLControls.RenderSearchFilters("mastercategory")
End Sub
End Class
Public Class BrandList
Sub New()
DropDownLists.Brand = HTMLControls.RenderSearchFilters("brandList")
End Sub
End Class
End Class
Hoping I'd be able to create the HTML for a Master Category drop down like:
Dim dd as New DropDownLists.MasterCategory
But that doesn't work, and upon reflection I think I can see why... it's not returning the string, but creating a new type.
So... my question is...
What is the correct way to achieve what I am looking for, which is, to be able to create these string outputs by typing
Dim dd As New DropDownLists
Dim list1Html as String = dd.MasterCategory
Dim list2Html as String = dd.BrandList
Without having to pass potentially unknown string parameters, or causing ALL properties to be created each time the DropDownLists Class is created, ie, only run the code for the output I need.
I'm expanding my comment to give you a clearer idea of what I meant:
Public Class DropDownLists
Enum ListType
Undefined
MasterCategory
Brandlist
End Enum
Public Shared Function GetList(ListRequired As ListType) As String
Select Case ListRequired
Case ListType.Brandlist
Return . . .
Case ListType.MasterCategory
Return . . .
Case ListType.Undefined
Throw New . . . .
End Select
End Function
End Class
I have a lable I want to update on a web form page from another class. I created an instance of that class then referenced a public method to do the update since I was unable to access the lable control directly. But when it reaches the public method it seems as if the controls were initialized and are not recognizable.
*...' calling class*
dim kws as new form2class
kws.setErrorLable("ERROR FOUND" & ex.message.tostring)
.....
called class
public sub serrorLable(Byval msg as string)
label10.text=msg
end sub
Am I missing something here? Thanks in advance
You can access the current page like this:
Page currentPage = (Page)HttpContext.Current.Handler;
Depending on where the label is in the page, you may need to use recursion to find the Label, but the above code will get you to the current page.
How can I make my own delete method to prevent that the data really gets deleted?
I want to set a datetime field when it gets deleted instead of a normal delete.
I read about overriding the submitchanges function, but I don't get it to work
Handle SavingChanges, go through the deleted items in the context, change their state to modified, and modify the field in question.
I wrote an interface IRequiredColumns with the properties CreatedOn, ModifiedOn and DeletedOn which every entity implements. Then I created this partial class for the context:
Partial Public Class Context
Public Overrides Function SaveChanges(ByVal options As System.Data.Objects.SaveOptions) As Integer
For Each entry As ObjectStateEntry In ObjectStateManager.GetObjectStateEntries(EntityState.Added Or EntityState.Modified Or EntityState.Deleted)
If TypeOf (entry.Entity) Is IRequiredColumns Then
Dim entity As IRequiredColumns = CType(entry.Entity, IRequiredColumns)
Select Case entry.State
Case EntityState.Added
entity.CreatedOn = Now
Case EntityState.Modified
entity.ModifiedOn = Now
Case EntityState.Deleted
entry.ChangeState(EntityState.Modified)
entity.DeletedOn = Now
End Select
End If
Next
Return MyBase.SaveChanges(options)
End Function
End Class
This works great for me!
If you won't find out how to override the delete function, you can create an ON DELETE trigger for every table in database, that does not delete, but sets datetime field.
I have an asp.net nTier application. The data access layer is a strongly typed DataSet consisting of multiple DataTables with DataAdapters. When the user logs in, they choose which database to connect to (from a table in the membership database). I need to pass the selected connection string into the DataSet object which will remain the same for that users until they log in again.
I'm thinking that the answer might be to create a partial class of the DataSet object where I can pass the connection string into the constructor. Im not sure how to go about this though.
Cheers
You could do this with a partial class.
Assuming your typed dataset is called HurrDurr:
public partial class HurrDurr
{
public HurrDurr(string connex)
{
this._connection = new global::System.Data.SqlClient.SqlConnection();
this._connection.ConnectionString = connex;
}
}
_connection is only initialized if it is null the first time the Connection internal property is accessed.
Finally got to the bottom of this. In a new module I created a partial class to the table adapter which is where I needed to change the connection string, one mistake I was making originally was not specifying the correct namespace.
Below is the partial class I created which allowed me to dynamically change the connection string of one of my table adapters for a table called tblOptions:
Namespace ds1TableAdapters
Partial Public Class tblOptionsTableAdapter
Sub ChangeConnString(ByVal newConn As String)
Me._connection.ConnectionString = newConn
End Sub
End Class
End Namespace
Thanks for the help Will, it got me going in the right direction.