OOP - Objects For Entities With Master Lists And Object Composition?
Feb 23, 2009
I'm trying to wrap my head about how to properly implement an OOP design for business objects that:
Have a "master list" in a database (ex. classifications)Are a part of another object as a property (i.e. object composition) but with additional properties
Here is where I'm stuck on the theory. Suppose that I have a Classification object, inheriting from the abstract class BusinessObject with the CRUD functions defined (MustOverride). This will give me:
[Code]...
What kind of other design could I implement here? It's obvous that I'm designing this the wrong way, but I don't see an easy alternative pattern. I don't want to repeat the code in the CustomerClassification class by not inheriting Classification and repeating all the field and property code, but I also don't want to expost CRUD functions to the CustomerClassification level. What am I missing in looking at the overall class design?
EDIT: Saving the classification level to the database will be handled by the customer object, because the database is legacy and the field for Level is defined in the customer table.
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Sep 17, 2011
I've just gotten started with development using Visual Studio (though this can be seen as a more language-generic question), and need done design answers regarding how to suitable relate a Database Entity/Table with an Class in-code.
Currently, I create a class who's attributes or iVars directly correspond to the fields in an Entity.
When I come to fetching all 'Customers from a Table' for example, I run a Select all statement against the database and for each result-row returned, I instantiate a new class Object where I use the Class' default constructor to set the instance variables. (I really wish there was a method like PHP's mysql-fetch-object()?)
I can then add each of these objects to say, a List(of Customer) and return it.
This doesn't seem like the best way to do it. If I were to change the Database schema, I'd have to reflect those changes in the class also.
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Oct 13, 2011
Basically I have the follwing:Dim ctx As New AdminCoreEntities Dim roles = (From r In ctx.Roles where r.Name.StartsWith("cust") Select r) 'list of System .Linq.IQueryable(Of AdminCoreModel.Role)
[code]...
The error i get when i run this is: Unable to cast object of type System.Data.Objects.ObjectQuery`1[AdminCoreModel.Role] to type AdminCoreModel.Role
Basically I have a many to many situation and I try to get all the Quicklinks objects queried by their roles and not quite sure why EF will cast to a single AdminCoreModel.Role when i.Roles is a collections of objects.
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May 31, 2012
Right now I have a viewmodel that contains three lists of inputs; textboxinput, dropdownlistinput, and checkboxinput. Each of these lists is a list of input objects, which contain four values; paramenums, paramname, paramtype, and value. I am using these input lists to generate a variable number of fields on a form dependent on how many objects each list contains.
My current problem is that I'm not sure how to validate the variables in the list objects with fluent validation. I know how the behavior of each list should behave with regards to returning Nothing, but I don't know how to code that behavior with FluentValidation.
[Code]...
The thing I want to currently do is confirm that in every object in each of my lists, they all have a value attribute that isn't nothing. Can I do this by validating the input model? Right now, the code works at confirming that the list itself isn't null, but the objects in the list can still contain all null values. Is there a trivial way to do this? Alternatively, should I have set my code up differently?
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Jul 29, 2011
I am getting following error whenever I want to use IIf function inside entity framework query.
LINQ to Entities does not recognize the method 'System.Object IIf(Boolean, System.Object, System.Object)' method, and this method cannot be translated into a store expression.
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Oct 16, 2011
I am struggling with the following - I try to add a value to a list, where the list is defined in a structure.
[Code]...
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Mar 15, 2012
I have collections of 2 different types - let's call them Cars and Trucks. Both share base class Vehicle, which has property Passengers.I want to merge them into a single collection ordered by that property. E.g., merge Cars and Trucks and order by Passengers.
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Dec 26, 2010
I have a Clients master object and then a number of child objects whose exact number is not known in advance such as Client-Contacts, Client-Payments etc, all of which have a one-to-many relationship with the Client master object.How do I define classes for such a scenario? Do I for instance create the master Clients class and can then I create an array of class somehow for child objects?
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May 4, 2012
[code]How do I update the ProdServiceID in the database using LINQ to entities?
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May 31, 2011
When I execute the code below I receive the error message: LINQ to Entities does not recognize the method 'System.Object CompareObjectEqual(System.Object, System.Object, Boolean)' method, and this method cannot be translated into a store expression.It seems to be occurring on the line For Each row2 in PCstudent.
[Code]...
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Jan 6, 2011
I want to let the user input objects to a richtextbox 1 object on each line, and somehow use Random.Next to select pseudorandomly a few objects, the number 'few' inputted in a textbox.
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Jul 7, 2010
I have a class that I wrote fairly early on in my vb.net programming experience which inherited from another class it really should have composed. The base class is a relatively generic nested dictionary-based collection; let's call the descendant class a "Car".Right now there's a lot of code that does things like 'MyCar!Color.st = "Red"' (I use the generic collection rather than real properties to facilitate data interchange with code written in VB6, and also to facilitate comparisons of cars; given three cars X, Y, Z, I can e.g. detect any changes between X and Y and apply those changes to Z).
Is there any nice way to refactor the code to use composition rather than inheritance?Which properties methods should the "Car" object wrap, and which ones should be accessed through a data-object property? Should a widening conversion be defined between a car and the collection object? Are there any gotchas when doing such refactoring?
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Sep 19, 2010
I accept both C# and VB.NET suggestion, even though I'm writing an app in VB.NET I have two lists of intergers
List1 {1,2,3,5}
List2 {2,4,6,7}
I want to have new List3 {4,6,7} which is composed of elements of List2 that are not in List1. I know I can write a nice For Each loop for this but I want it done in LINQ I've been looking for such methods at Enumerable Methods, but I can't find it.
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Feb 3, 2012
When you type sender. IntelliSense lists 5 methods and yet if you type sender.Left or sender.top these will work. Why don't these properties show up as available for use via IntelliSense.
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Aug 5, 2011
I am getting the following error at runtime:"Object reference not set to an instance of an object." - the code in question in my code-behind is as follows:Dim MinDateDataView As DataView = CType(SqlMinDate.Select(DataSourceSelectArguments.Empty), DataView)Dim MinDateDataRowView As DataRowView = MinDateDataView.Item(0)
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Sep 22, 2011
Custom Object Master-Detail Data Binding
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Sep 6, 2011
Limited to using v2.0 of .Net framework (we use VB.net) due to environmental constraints on our servers.I've got an ASP.net webpage which pulls data from a webservice that performs checks on user accounts in active directory. Operators can check multiple accounts at one time using the web interface. The webservice returns a list(of AccountCheck) objects which themselves contain single properties like username, email address, and List(of AccountError) objects which contain multiple properties.[code]What I want to do is using some kind of repeater, create multiple panels or divs which contain labels showing the username, email etc, and a gridview which has the accounterror list bound to it to show all the errors. The users could be checking 2, 5, 7 accounts at once, and is dynamic.
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Apr 1, 2011
I have two lists. One list is a list of names, the other list is a list of how many times each name is found in the first list noted in the database
so...
Nick
John
Jim
Jack
is the firs tlist
10
13
13
2
is the second list. Nick had 10, john 13 and so on.I want to sort the second list from large to small, but have the index for the first list still linked to the correct amount of calls.i do it this way so I can
for x = 0 to num_of_names
string = lst_name(x) & "-" & lst_count(x)
next x
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Sep 9, 2011
I have an asp image within my "default.aspx" page.I set cookies on my masterpage vb file and depending on the cookie set, I want to show or hide this image.
default.aspx
<asp:image ImageUrl="/images/myimage.jpg" runat="server" ID="myimage" Visible="false"></asp:image>
mymaster.aspx.vb
[code]....
I get the following error:
'myimage' is not declared. It may be inaccessible due to its protection level.
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Jan 20, 2010
I am having some real issues with this one. I have a class which contains two other objects...but I cannot seem to instantiate those sub objects. Here is the code for my class:
Option Explicit On
Public Class Boot
'A collection of Heads and Shells
[Code]....
Notice the count for my two objects, Ohead, and oShell, is zero. Im not sure why this doesnt instantiate properly, as I believe is what is going on.
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Nov 15, 2010
I am trying to create an object browser similar to what VS2010 uses for the quick watch window. I can use reflection to iterate through the properties and display their names and values until I get to the point in an object where the property is an object of my own creation and not a system type. I can't seem to find the correct approach to be able to iterate the properties of these "sub objects".
Below is the just of what I am trying to do
Public class myClass
property myprop a string
[code].....
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Jan 20, 2010
I am having some real issues with this one. I have a class which contains two other objects...but I cannot seem to instantiate those sub objects. Here is the code for my class:
Code:
Option Explicit On
Public Class Boot
[code]......
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Jan 20, 2010
I am having some real issues with this one. I have a class which contains two other objects...but I cannot seem to instantiate those sub objects. Here is the code for my class:
Code:
ption Explicit On
Public Class Boot
[code].....
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Jul 12, 2010
I have a managed class that uses a COM that looks like this.
[Code]....
Since I am using an unmanaged dll through a COM-Interob dll I am wondering if I need free the innerobj manually or if the gc is smart enough to do it automagically if I call ReleaseObject() My class implements IDisposable and I do the following atm: Runtime.InteropServices.Marshal.ReleaseComObject(myobj) Do I need to take care of releasing all inner objects that are created by the COM Object or not? And If I do have to do it, does the order matter (first inner then parent vs parent then inner)?
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Apr 20, 2010
So I've created a series of objects that interact with a piece of hardware over a serial port. There is a thread running monitoring the serial port, and if the state of the hardware changes it updates properties in my objects. I'm using observable collections, and INotifyPropertyChanged.
I've built a UI in WPF and it works great, showing me real time updating when the hardware changes and allows me to send changes to the hardware as well by changing these properties using bindings.
What I'm hoping is that I can run the UI on a different machine than what the hardware is hooked up to without a lot of wiring up of events. Possibly even allow multiple UI's to connect to the same service and interact with this hardware.
So far I understand I'm going to need to create a WCF service. I'm trying to figure out if I'll be able to pass a reference to an object created at the service to the client leaving events intact. So that the UI will really just be bound to a remote object.
Am I moving the right direction with WCF?
Also I see tons of examples for WCF in C#, are there any good practical use examples in VB that might be along the lines of what I'm trying to do?
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Mar 15, 2012
I don't know if I explained this in my title, this is what i want to do. (In VB on a active server page) I have 5 buttons called but1.....but2. Right now I have the following code to make them invisible
but1.Visible=false;
but2.Visible=false;
but3.Visible=false;
but4.Visible=false;
but5.Visible=false,
Is there a way to access the objects by using a string, example
for(i=i;i<6;i++
items("but"+str(i)).visible=false
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Mar 3, 2009
OK - for starters - I'm not even sure that the title of this thread accurately describes what I want to do - but I had trouble verbalizing it. So I will give this a try: In my application, I have a custom object, call it myObject. In addition, I have another custom object called myObjectList which is basically a List(Of myObject).
Up until this point, all of the functions that I have been working with in my BLL and DAL have been shared - I haven't needed a specific instance of my object thus far. I currently need to write a function that finds a particular myObject within myObjectList and returns to me myObject. I know that the List(Of T) has a find method, but from what I have read so far - I don't think it is what I want (doesn't it return true or false? -and also, do I need an existing object to pass to it to see if it is in the list?)
[Code]...
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Sep 25, 2011
Is it possible to find a complete object in list of objects?
how to find x in list1 if it exists without comparing a single property like ID ?
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Sep 14, 2011
Is there a simple way to remove Objects from a List by using a specified value?I add 2 persons to a List, how can now I remove a person by a name without using any Loops? (if possible)
[Code]...
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Sep 15, 2011
I need to query an array. I have tried to use LINQ but with no success.
Here is a simplified structure of Insurance
Public Class Insurance
Public _typ As String
Public _numb As Number()
[Code]....
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