VS 2008 - How To Manage A Class Relationship
Apr 23, 2010
how to manage a class relationship I have these objects: A Layouts collection which implements a BindingList of Layout.A Parameters collection which implements a BindingList of Parameter. Each layout is to hold a set of settings, as defined in the Parameters Collection. Each layout should have a setting for every parameter, but the choices are constricted to the list of possible settings, kept in the Parameters object. For each setting there is only a single value. So it would look like this:
Layouts' Layouts; Collection [BindingList(Of Layout)]
Layout 1' Layout; Collection [BindingList(Of ...?? )]
Color Red' Parameter Key, [referene to parameter object..or..?]
Time Hour
Now, when I create a Layout object, I shall be restricted to chose one setting from each parameter, as already defined in the Parameter object, and assign to my layout object. And if I add/remove parameters, parameter settings, or the setting values, that should reflect in each layout; set to a default value, or deleted.
what type of class/object relationship shall I use for this Layouts collection in respect to the Parameters collection? I have no good understanding of the terms such as "inheritance", "implements", "interface", "abstract class" etc.. So I'm not able to see what concepts I need to study to make this come together nicely. Of course I could make a bunch of manual methods that keeps track of these things, but I have a feeling that I should make some type of relationship between these collections, which can make this somewhat easier..? I want to keep the collections as BindingLists down to the lowest level, in order to have two-way databinding with the UI controls.
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Feb 3, 2010
Basically, I am trying to write a LINQ to Objects statement where the relationship is a grandparent, parent, child relationship. (You could also call it a Master Detail relationship.)
Dim coverages As New List(Of Coverage)
Dim coverage As Coverage
For Each rl In oClaimsPolicy.RiskLocations
[code].....
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Nov 10, 2010
I tried to make a class to manage the communication with Excel, but I am having problems.
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Feb 13, 2010
How best to manage multiple dat files for serializable objects of the same class. If one of my data files goes past a particular size, I want to create a new file. I then loop through both files when I do processing. Is there any easier way to do this and what's the best size to do this at in terms of performance?
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Sep 23, 2009
My VB project is large enough that it requires several files. It was originally developed as a Console App and I created each file as a MODULE. All modules could use subroutines, data structures and constants from other MODULES and everything worked fine. I needed to add basic windowing to the app and this required that the app be converted from a Console App to a Windows Forms App. The main window is Form1 which is not a MODULE but a CLASS. The problem is that some MODULE based functions cannot access subroutines, data and constants that are defined within the CLASS Form1 unless they are incorporated into the CLASS file and this makes the CLASS file very large. If I add a new Class file to the project, it also cannot interoperate with Class Form1 in the same way that multi-MODULE code interoperates.
How does one spread CLASS code across several files and still allow it to interoperate as if it were in a single file? Alternatively, how does one create several CLASS files that operate the way multiple MODULE files operate.I am sure that there are all kinds of best practices that I am violating but the goal to to get some prototype software working and interfaced to some lab equipment.
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Jan 4, 2011
I have two tables which need to be connected using a one-to-one relationship. In SQL Server 2005, how would I add this relationship to the database diagram, do I just leave the relationship blank? Is there any pre requisite queries I have to add? How do I connect these tables in VB? .. the same way I would connect a one-to-many?I need the Student table to be linked to the Class Table where One student can be in only 1 class.
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Jun 17, 2009
I'm new to both SQL Server Express and VB2008 Express or any other kind of language for that matter..I'm trying to create a form using a typed dataset created using the Data Source Configuration Wizard that contains two main tables and a third that creates a many to many relationship between the first two.Is this possible as when I examine the dataset in the Data Sources window, the middle table shows up as a related table under each of the main tables but neither shows a third related table.How can I show synced data from all three tables on my form. Is this possible using the Configuration Wizard or does it have to be done in code?
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May 10, 2011
I'm trying to create a form using a typed dataset created using the Data Source Configuration Wizard that contains two main tables and a third that creates a many to many relationship between the first two.
Is this possible as when I examine the dataset in the Data Sources window, the middle table shows up as a related table under each of the main tables but neither shows a third related table.How can I show synced data from all three tables on my form. Is this possible using the Configuration Wizard or does it have to be done in code?
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Jul 2, 2010
I'm going to describe this as simple as possible, and it a typical setup for a database...
I have 1 DataSet, 2 DataGridViews (DGV), and 2 BindingSources (BS).
The DataSet has 2 tables and 1 Relationship (FK).
Table 1 is a employee table
Table 2 is timeclock data.
Both tables contain a column: EmployeeId
FK is linked to EmployeeId of both tables.
DGV1 has it's datasource=BS1
BS1 has it's datasource=DataSet and it's DataMember=Table 1.
Thus DGV1 shows Table 1.
DGV2 has it's datasource=BS2
BS2 has it's datasource=BS1 and it's DataMember=FK
Thus DGV2 shows Table 2 filtered by what's selected in DGV1.
Now when I use the mouse or keyboard to select a cell in DGV1, the relationship causes DGV2 to update to only show data from Table 2 where the EmployeeId row equals that from the selection in Table 1. With me so far?
Well all that works great. But what if I need to programmatically select a row in Table 1 to cause Table 2 to update? I've tried everything I can think of, but Table 2 NEVER updates when I attempt to programmatically select a row or cell in Table 1.
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Mar 27, 2011
I'm working with VB2008 and I was wondering how to get the treeview to show the relative, relationship, key ect....vb6 Example
Treeview.Nodes.Add Relative, Relationship, Key, Text, Image, SelectedImage
I would like to be able to use the treeview this way but if there is another way can someone let me know, I have searched the net and have looked in a few books and cannot figure this out.
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Nov 12, 2010
I've a little problem to how manage a TCP client exception. I've declared a client in Form1 as described below:
[code]...
I want to manage the Exception (ie when my client is offline) by Try..Catch, but unfortunally inside Form1 I can't. How can I bypass this problem?
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Aug 1, 2009
What would be the best way to manage multiple Picture Boxes?I am thinking an array, but if that is so, how would I build this array, and what would be stored in it?
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Dec 19, 2009
how I would be able to make the click of a button scan a certain directory for certain files like .txt files, and display those files in a text box, or if not a text box some other viewer.
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Jun 5, 2010
I have a function which does some processing. Lets name that function DoWork. This function takes some inputs as structure and a string. Now I want to start two threads which would read some elements in an array and then call DoWork with some data and value of that element. DoWork would do processing and thats it. I want two threads to run side by sid.
So I tried to write code but kinda failed. I wrote a function which starts a thread and calls DoWork. Now DoWork accepts structure and string etc. But when we do say abcthread = new threadig.thread(addressof <sub name>). here we cant pass any-value except object. That was first problem.
Anyway, main problem is after the thread has finished processing DoWork, how do I find that out and tell that thread to take another element from array and start again. This has to be managed for both the threads. I need to find out which thread has finished first and tell it to start again with another value. I have usually used one thread but not two in this way.
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May 26, 2009
When i try to stablish a relationship in dataset designer of these two types i get a "no matching field type" error I'm working with an accdb database
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May 17, 2012
I use Visual Basic 2008 Database is Mysql Three tables:
[Code]...
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May 15, 2011
I remember we were taught BASIC (Beginner's All Purpose Symbolic Instruction Code) language in school, when we were in 5th grade. It was purely in DOS-Mode and we basically used it for drawing. Then I learnt Visual Basic 6.0 quite a few years basic. I neve found a similarity between them
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Jun 21, 2010
I am trying to create an list or an array of a class.Here is my "Ingredient" class that I am trying to create a list of:[code]In my "recipe" class, I am want to create a list (or array) and I am drawing a big blank on how to do it. Can anyone point me in the right direction?
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Nov 21, 2009
I am searching for the Component Class. When I go to "Add New Item" ,in my project their is no Component Class Item in VS 2008. I would like to Drag and Drop control onto my new class and I can't see how to do this ?
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Apr 11, 2009
I have a 'property management class' that contains several functions and properties. I have several other classes that use the 'management class' as a property to derive the value of several of its other properties.Is there a way for me to reference the outer class from the 'management class' functions without having to pass it as a parameter? I ask because several different classes can have this 'management class' as a property and am having a hard time typing the parameter.
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Jul 21, 2011
My issue involves relationships and cascaded effects between properties, and I'm wondering what best practices are on this.I have a class that contains a list of varying length of numbers. When editing the list, sometimes the user prefer to set a TargetSum, so that the program enforces the list will always add to this sum. I am accomplishing this by programmatically setting the final element in the list such that list sum = TargetSum. For example, if the user chooses to UseTargetSum, then sets TargetSum = 10, then creates a list of length 4, and enters 1, 4, 2 for the first 3 elements, then the final element is programmatically fixed to 3. The user cannot change the final element themselves.
I do this behind the scenes by handling all necessary events, such as a list element value change, list length change, and the UseTargetSum option change. For each event trigger, it recalculates the last element's value.It works but then there was a bug when loading saved data. If a list is loaded by sequentially adding the elements, the handlers modify each entry. Regarding the example, when the first value of 1 is entered, the handlers say "a value was just added, the sum should be 10, there is currently only one element, so it needs to be 10". So the first element gets changed to 10 behind the scenes. When the second element is next added, the handlers say "a value of 4 was just added, but the first element is already 10, so it should be zero." At the end of the load, the final list reads 10,0,0,0 instead of 1,4,2,3.
I know it is possible to rearrange the load procedure such that I get the correct list. For instance, I could avoid enabling the TargetSum event handlers until after all the data is loaded. The list would first be created as 1,4,2,3 and then the handlers would change nothing.
But this experience makes me wonder if I am opening the door for other sneaky side effects. It seems you should be able to load data without worrying too much about an implicit ordering. It also seems unusual to have "cascading" effects between class properties. Is there a more accepted approach?
The other alternative I'm considering is to only enforce TargetSum only inside UI forms. Ie, when you know it's a user making the change, then enforce the TargetSum, but otherwise leave the core class logic alone.That way database loads, etc, are left unaffected. But I guess the downside of not having ubiquitous enforcement is that opens the door of incorrect sums via some unforeseen complication.
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Mar 14, 2011
I have made a small "front-end" application for an Access databasefile.
I set up 3 tables with relations in Access, and added the database as a datasource in my project. I have done no database programming, and the app has worked nicely for about 2 years. It's a simple master-detail form with 2 datagridviews dragged from the datasource window.
Yesterday I opened the project to add a new form. The form is just a "setttings form" with no database activities.
When I press F5 - the main form do not start, and I get the error message "DataMember property '{0}' cannot be found on the DataSource." - where the property name is the name of one of the 2 relationships in the datasource.
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Feb 22, 2009
Im would like to create relationships between my tables from different database. im using VB 2008 and SQL 2008 as my database. Is the relationships should be made on my database itself or tru coding in my VB? If either which how can i do that.
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Dec 15, 2011
How do we create relation ships between tables using a sql query?im using MS Access and VB.net.
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Jul 13, 2009
I cannot figureout to which class ItemStatus should link to!please refer to my blog in the following link to detail description of the issue
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Sep 8, 2009
I'm using a dataset class written by others who have defined the foreign key relationships between tables using the tools in the schema diagram. I'm binding the dataclass to a windows form. I'm running into an issue where I have an existing header record and I'm trying to insert data into a child table via a grid programmatically. The child table contains all keys for data. As the grid is bound to a binding source, I'm simply adding rows directly to the grid programmatically.
When I attempt to save the data, I get the error ForeignKeyConstraint FX_Activity_UserRoleActivity Requires Child Key Values (4) to exist in the parent table. The value (4) is one of the foreign key values and it does exist in the parent table. The error occurs when I tell the bindingsource associated to the child table on the form to EndEdit. Looking at the XSD file for the dataset, both foreign keys are set up for 'Both Foreign and Key Constraint' with Cascade set for both update rule and delete rule. Accept/Reject rule is set to none.
Running a SQL trace, I confirmed that SQL Server is not generating the error, so it is occurring on the client application somewhere. First what does the error actually mean? Second, does the configuration of the foreign key relationship in the dataset's XSD file have anything to do with it? If so how should the foreign keys be set up between the tables? If it isn't how would you go about troubleshooting this issue as stepping through the code ends with the .EndEdit call to the binding source.
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May 8, 2010
StudentId is a foreign key in StudentSubject,What I want know is how do I illustrate the relationship between the two tables is many to one
StudentSubject
StudentID Subject
148 Art
148 History Of Art
145 English
145 Poetry
128 Chemistry
128 Physics
128 Biology
123 Math
StudentLocation
Student RoomNumber
123 1a
145 3b
148 4c
128 2a
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Jun 1, 2009
If I a many-to-many relationship between Users and Roles and I have an instance of a User entity and several Role Ids can I insert a relationship between the two types of entities without having any other Role data and without doing a select on the Roles first? Update:
I might not have been clear enough. I don't have an instance of a Role, only the role id. Is it possible to create the relationship between User and Role without filling a Role object from the database first?
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Jan 18, 2011
connection here and declaration of variable
Dim i As Integer
Dim chk As CheckBoxList
chk = CType(Me.FindControl("chkBx1"), CheckBoxList)
For i = 0 To chk.Items.Count - 1
[Code]...
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Jun 9, 2011
I am trying to input value to AppSchedNumber into my AppInfo table which is the primary key of my AppExamSchedule (auto inrement). The problem is I can't insert on my AppInfo because my AppSchedNumber on my AppExamSchedule should be the same.
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