Collection To Place These Objects In For Easy Reference?
Nov 11, 2011
I have an error while using a collection that has been stumping me for years.I wrote a class to allow users to write equations in a txt file using RPN (stack based notation).The class runs through a select statement while reading the equation and then ends up with a final number as the answer. I have a collection to place these objects in for easy reference. For whatever reason I get random object reference not set to an instance of an object errors when there is nothing in the program that would remove objects from the collection, kill objects, or change the collection in any way. It is possible for one thread to call the calculate function while another thread calls the CurrentValue property. I'm not sure if this could be causing the error, but once it happens I get an error every time the program enters that code until I run out of memory.
I created a custom class for a custom object. I instantiate like so[code]...
Now, I have two problems. First, right now this is just overwriting the same object properties, again, and again. I need to somehow dynamically name the object. Then, I need to place these objects in an array so I can iterate through them...
Okay I've been wondering about this for a while now, but whenever you assign variable values to objects they tend to just become references to the original object
For example:
Dim copiedCollection As ListBox.ObjectCollection = ListBox1.Items For Each L As String In copiedCollection If L = "Goodbye" Then ListBox1.Items.Remove(L) Next
As soon as it encounters the string "Goodbye" and removes the item from the listbox, the program will throw an error saying the the collection (copiedCollection) has been modified. How can I make copiedCollection a true copy (not a reference) to the Listbox1.Items collection?
I have founfd numerous ones on the net, but they all only do these complicated RegEx for zip codes, html, address, credit card numbers, etc etc,All I want to accomplish is when the user searches for "commend", they get only every occurence of the word "commend". NOT commendeth, or commends, or some other variation.[code]
Lets say I have 30 text fields in a Frame on my form, and I want to set them all to disable (so users can't edit them).Is there an easy way to walk through those fields without having to create an array of text fields?
I.E., in ... VB 6, with an array of text fields, I can do something like this: For i = 0 to 10 txtfield(x).enabled = true. Next i
Is there something in VB.NET where I won't have to use an array of controls, something like this (assuming all txt fields are in a frame):
I have a VB.NET web app that is about 2000 lines of code, contains about 20 different subroutines, and about 50 different functions.Is there an easy way to "rewrite" this to take advantage of classes and objects?
I am learning Visual Basic 2010 and I am working on a space combat program for my own education and amusement (a simulation of the Honorverse space combat system). I have a routine to add ships to the enemy ship roster and then place them randomly on the viewscreen. When I step through the sub with the debugger, it works fine, but when I run it without stopping, it wants to place all the objects in the same place on the screen. It's actually assigning 2 random numbers pertaining to the size of the viewscreen and assigning those numbers to GameObjectScreenLocation through GameObjectWorldLocation.X and GameObjectWorldLocation.Y. The objects are fully initialized to 0 in their constructor, FYI. Code is below:
we have 3 classes:Class S, class A, class B / A and B inherits S.A has a property A1 and B has a property B1.we also have a collection of objects that has A and B objects.ex.
Dim c as Collection = new Collection c.add(new A) c.add(new B)
Now we want to make a general object that will read from the collection.
ex . Dim obj as S
how can we cast obj in order to see properties A1 or B1 according to the class;
suppose I have a collection of objects of different classes (like controls in a form), and all of their classes have a MyMethod extension method. How do I have the appropriatemethod be called for each object, depending on its type?or example,
For Each ctrl In Me.Controls 'call ctrl real type's MyMethod Next
i've researched and written a generic class (all my objects are the same structure) and i'm was just working on the collection using a hash table but i've just read a comment within (url...) in this forum...that we shouldn't use hashtables at all with vs2008.i actually need and object collection that contains other object collections within them.the application i'm trying to write is relatively simple (but i'm new to vb.net)it keeps track of the time for weight lifting training/workouts.a workout consists of 'say' a bench press, military press, curls, dead lift, etc within the "bench" you have 1,2, or 3 sets (how many times you do "the bench", within a set you have 1,2,3 or 4 lifters, each lifter does reps.then it starts over with military press..i guess i could base it on a treeview type structure (with parent child type relationships) but i usually think in terms of collections it appears that a collectionbase has no key and i'd have to keep track of them on my own...
I'm trying to figure out the lifetime of the tmpTabPages in the following bit of code. Lets assume the form has an empty TabControl named MyTabControl, that there's a collection of strings called NameCollection.
So I have a collection of Razzies created from a Collection of Bloops. I retrieve this collection using a Linq query. Reference:select-certain-properties-into-another-object for the query.I would like to know if it is possible to run a method on all of the newly created Razzies before returning the collection, or even right after, just without using a for-loop.
I tried ths: Dim results = From item In bloops _ Select New Razzie() With _
I'm implementing a customized Graph algorithm in vb.net, and I'm having the following problem:
Supose the code:
dim col as new collection dim myC as new system.collections.genericList(of myClass) dim obj1 as new myClass dim obj2 as new myClass
[code].....
'In the next statement, the myC2 inside col collection will be decreased to contain 'only obj1, like myC. I supose this is for myC and myC2 contains only a pointer to 'objects obj1 and obj2 as well col contains pointers to myC and myC2 myC.remove(obj2)'The problem is that I have to only copy myC to myC2, like a ByVal argument in a function,'instead a ByRef argument, in order to mantain a copy of objects in myC2 while these 'objects should be removed from myC. How should I do it?
I have a question. I have a class of Cars that I need to display in a simpli-ish string if they will be sold or not base on their number.
[Code]...
I'd like to display a simple string like this:Cars to be sold: 1, 3-5, 7-8, 11, which is based of the .Sell value.Is there some kind of heuristic to create this kind of string in .NET or is it just a bunch of for/each and if/then and redimming of arrays?
I am trying to maintain a total for multiple collection objects in a class. When I create a new object, it resets the total to zero, only adding the current value being passed to the function. I have tried to use a static variable, create a second variable to hold the old total while adding the new value. The base class holds the total value, while the sub class creates the new object that holds information. I am passing the new value to a function in the base class adding the new value to the total when each new record is created.
i have a sql query that can bring back a large number of rows via a DataReader. Just now I query the DB transform the result set into a List(of ) and data bind the Grid to the List.This can result occasionally in a timeout due to the size of Dataset. I currently have a three teir setup where by the UI is acting on the List of objects in the business layer.
I have an object of type Dictionary(Of Int16, Polygon) and which contains sometimes up to 15 or so Polygons that i am creating bitmap files with the Polygon. This can take like 20 seconds sometimes so i was trying to pass the full Dictionary to background worker as an argument but i get an issue when trying to access each individual Polygon inside of the Dictionary because the Polygons still belong to the UI thread. How can I access the Polygons inside the Dictionary with the backgroundworker?
Dim worker As New BackgroundWorker AddHandler worker.DoWork, AddressOf MeasurePolygons AddHandler worker.RunWorkerCompleted, AddressOf WorkerCompleted worker.RunWorkerAsync(PolygonCollection)
that is how im calling the thread. PolygonCollection is the Dictionary(Of Int16, Polygon) that contains all the polygons that i will be creating a bitmap file out of.
I'm having problems doing a sort of a custom collection. The collection is Device Classes which is a collection of Device Class. My sort does not produce an error but the treeview control shows nothing. I am not sure what I am missing. I'm guessing just a simple sort won't work here but I don't know what I'm missing in my code. Here's the code that creates the collection
[Code]...
Simply sorting the treeview will not work because it throws off the display of related info for a given device in listview controls. The collection itself needs to be sorted before the data is added to the treeview.
I was just curious as to whether after you have added all of the Parameters to the SQL Command Parameters Collection. Is there a convenient way to iterate or loop through the Parameters and make Assignments to the SQL Command Parameters Values Property?
I have a GUI which allows the user to select a report to view/edit. When the user selects a report, it shows the Items in the report. The Item has many properties - most of which are binding properly. One of the properties is Owner, and this is bound to a ComboBoxColumn.
Report
Items
Owner
I have done something very similar to this a few times and had no problems when I set the DataPropertyName, DataSource, ValueMember, and DisplayMember. The only difference is that this time instead of the Item type having an OwnderID it actually has an instance of the Owner object.giving the items bound in the list a self-referencing property that allows them to return themselves for the purposes of setting the ValueMember.However, When I bind it this way:
I get a lot of errors like: Unable to cast object of type 'System.String' to type 'Owner'.
and:
The following exception occurred in the DataGridView:
System.ArgumentException: DataGridViewComboBoxCell value is not valid.To replace this default dialog please handle the DataError event.I was able to get around some of these errors by binding it like this:
and also by making the ToString function on the Owner display the OwnerName property. This seems pretty hacky though - and I think I'm misunderstanding something fundamental as it still does not function properly.
ArialRegular8 | <Corresponding Font Object> ImpactItalic10 | <Corresponding Font Object> TimesRomanRegular12 | <Corresponding Font Object>
These font types come from an external library, the real type is DocumentFont, I prefer not to store just values and recreate the font object later, so I need to store the object, and i want to be able to call Contains() later without looping. like for example Dictionary (of T Key, T Value), is this the best option? Also, to be able to call Contains(), i will have to overload function Contains() using an Interface or this is already built-in in some Collections / Dictionaries when using a String as Key?
I've got a multi-threaded app - that is using a global COLLECTION of objects.I'm starting to think that objects - when copied to objects - are really just reference pointers to the "single object" in memory - as they would be in JAVASCRIPT (too many languages At any rate - this code - when taking the object from the collection to work with is it making a new object to play with or is it working the single object that actually resides in the collection?
i have a user define object which i'm initializing with data from external datafiles.... the purpose of this object is to reduce the amount of disk/data access and processing required every time i need to add an instance of this object to a collection.so, whenever i add a copy of this object to a collection, i would simply reference the "base" object, and avoid having to process all the data and perform the conversion and so on...the issue is when i add the object
Collection.add(Base_Object, Key)
the collection ITEM is a Reference to the base object and not a copy.
I often have a class defined and I also define another class that is simply a collection of the other class. To do this I found it easiest just to define the other class as Inherits List(Of Type). The reason I define a collection class is to add extra functionality to the collection. Take the following code for example.
Class Car Property Name As String Property Year As Short
[Code]....
how can I define my own collection so that I can reference it by index or name like that. Right now I can only reference it by index.
and I can't find a way to get a reference to the Screen. I've checked my references and they seem fine but I may have missed something. Anyone experience this or know of a bug?
When it comes to creating trees or collections, sometimes I want child elements to have a reference to the parent. Obviously it is important that the parent and child references to each other remain in sync. It seems natural to have code in the parent "addchild" and "removechild" methods that updates the child's parent reference.t also, the reference to the parent should probably be readonly, so it can only be changed at the appropriate time.Two examples in .Net that I've seen are the TreeNode and datagridview controls
I am writing a simple control translation function that reads an XML file containing control names and their localized text. Within the application, each time a form is loaded, it iterates through every control and tests to see if that control is defined in the XML file. If it is, it then sets the control text to whatever localized text is defined in the XML file.
There are some tests and additional requirements (i.e. nested loops) for TabControl and MenuStrip etc., but the control that is giving me the most trouble is the ContextMenuStrip.[code]...
I created a .net assembly, which works perfectly if I create before runtime. But i'd like to know if it's possible to reference at runtime. The reason is because i'm creating an application which will be used in several servers, and it will be reference that same .net assembly, but the .dll file will be in different location per server. I know that when I reference before runtime, the .net assembly it will be pointing to is from the original (or at least that's what I think).
