C# - Extending An Object And Any Child Collections?
Jul 30, 2009
I have an class named Foo. This class contains a collection of child objects of type FooChildBase, but I also have a further class of type FooChildTwo which inherits from FooChildBase.
Class Foo
Public Children As IList(Of FooChildBase)
End Class
Class FooChildBase
[code]....
What I would like to do is have my FooSpecial Class treat it's Children collection as if they were FooChildSpecial objects, but still be able to add FooChildTwo objects to it. Is this possible and if so how can it be done?
EDIT:I need to FooChildSpecial class to wrap any of the objects in the Children collection with the extra values, whether they are FooChildBase or FooChildTwo?
Im working with MDI parent/child objects. when closing the child objects i need the child to check to see if it is the last child object before closing. i couldn't find anything on google, maybe im searching for the wrong thing.
If I defined a ENUM in a base object with serveral default values. When I inherit from the base object I want to add more options the the ENUM list which are specific to the inheriting object.
For example my base could have a ENUM called Direction with values: None ALL Stop Start
I create a new class call Compass which inherits the base class and what to add the following to the ENUM Direction. I create a new class call Navigation which inherits the base class and what to add the following to the ENUM Direction. So, In my inheriting class haow do I extend the ENUM.
If I'm extending OnCreated for a LINQ to SQL table object, is it possible to get a reference to the data context to which the table belongs? For example, if I add a property to the data context:
Partial Class MyDataContext Private _myValue As String Public ReadOnly Property MyValue As String
[Code].....
I don't want the property on the data context to be Shared, because it could be different per instance. I've been pouring over the designer code to figure out where the reference might be, but no luck yet.
I have a question specifically about getting the current cookies set to a particular visitor on an ASP.NET webpage. I understand you need to use Request.Cookies - and by default it returns a collection of all cookies set, as an HTTPCookieCollection. However, the MSDN documentation states that you do: Request.Cookies("Username") as an example, in order to fetch an individual cookie and then compare whether it is set, etc. All fine and dandy but why adding parentheses and a string does the type suddenly change to HTTPCookie.
I understand HTTPCookie is for dealing with individual cookies and HTTPCookieCollection is for dealing with multiple cookies at a time for like iteration purposes, etc., but I don't understand when on the MSDN documentation it explicitly states that the Request.Cookies property (the Cookies property) is of type HTTPCookieCollection, and if you do what I explained it changes the type (I can see this from IntelliSense) and it does not state this happens in the MSDN documentation. I'm not asking about the MSDN documentation lol, but why this happens when adding the parentheses and a string denoting the cookie name. I'm still pretty new to Visual Basic. By the way, I'm doing this all in Visual Web Developer although using VB as the language of choice.
given the following class structures:[code]I add the following property to MyList, trying to answer questions like "find out the number of elements with specified type, say Derived1, inside MyList?"[code]
My colleague and I have recently upgraded our projects from .NET Framework 1.0 and VS2002 to .NET Framework 2.0 and VS2005. We also applied the latest VS2005 service pack.
Our problem: normally when debugging we use the QuickWatch window to drill down into and view collections of objects belonging to the parent object we are "watching". THIS NO LONGER WORKS...instead, we get a message in the value line against the object collection saying:"In order to evaluate an indexed property, the property must be qualified and the arguments must be explicitly supplied by the user."This is incredibly frustrating, particularly when we have large nested collections of objects.We are pretty sure this feature was working fine after we upgraded, but we are not so sure that it was working after we applied the VS2005 service pack.
I have a VB.NET project where I am able to iterate through the keys and values collections of a dictionary object using an index:
MyDictionary.Keys(idx) MyDictionary.Values(idx)
When this code is taken from the test project and placed into the real project I get the following error:
'System.Collections.Generic.Dictionary(Of Double, String).KeyCollection' cannot be indexed because it has no default property.[code]...
In the line in sub search that says "dtf.Keys(idx) = 0" place your cursor after the right parenthesis and backspace you should get a tooltip that says, "<Extension> ElementAtOrDefault(index as Integer) as Double - index: the zero based element of the index to retrieve.
I have these objects:[code]Using LINQ I need to take a List(Of MakeInfo) and a List(Of ModelInfo) and aggregate the StockInfo from ModelInfo into the List(Of MakeInfo).So for each MakeInfo I will have a total count of all stock where MakeInfo.Name = ModelInfo.Make, and also a minimum price.I think it's going to be something like this, but I'm having trouble accessing the nested object and not sure if it's going to be possible with a single query.[code]
I'm checking If a border's child property is not set to nothing or equal to a given element, but whenever I run the program, it says that it's set to nothing and crashes. Here's my code:
If Not Me.Child.Equals(Nothing) Then ... If Me.Child.Equals(value) Then ...
Both gives an error. What should I do to pass these lines? Also in C# it would look like this:
if(this.Child != null) ... if (this.Child != value) ...
I have a series of API calls that are returning J# data types. I have been able to convert most of the data types (Integer, Boolean, Double, Float, etc) just fine.What I need to do now is convert a java.Util.Collection to a VB .NET collection (ArrayList)
Here is my attempt:
Public Function MakeDotNETCollection(ByVal javaCol As java.util.Collection) As Collection Dim dotNetCol As Collection
[code]....
I keep getting a runtime error "Unable to cast object of type 'AbstractListlistIterator' to type 'System.Collections.IEnumerator.
I am constructing a collection of objects, and need to use inheritance on a base class - I have been trying for hours in various ways and can't get this to work whatsoever - the error is always "Object reference not set to an instance of an object." The idea in the example below is that an object is instantiated, and within that lies a collection of Students when I try to access the oDemo.Students(0).Name property the error is raised. Otherwise the object appears to have instantiated OK.Here is the code being used to instantiate and access the class (from ASP.NET).
Dim oDemo As New MyDemo.Students lblTest.Text = oDemo.Student(0).Name Here is the sample code from the class library:
I am using Visual Studio 2005 and am writing a SSIS package. In the package I have a VB.Script that looks at a directory on a server and creates a list of the files. I then have a store Proc that looks at a table and gets a list of files that matches the files in the first array. The result is a fullresultset. The next step I need to create a 3rd array that only contains the rows from the first that are not in the second. However, I am getting the following error. Error: The script threw an exception: Unable to cast object of type 'System.Object' to type 'System.Collections.ArrayList'.
What's really the point in using the former?It's hard to use linq if I used the former. I have to convert that to an array first which is difficult because there is no (asarray) function.I think I would change all of my code that's using System.
Collections.Specialized.StringCollection to System.Collections.Generic.List(Of String)
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.
I occasionally find myself passing this or Me to a child object. Such as this condensed real-world example...
Public Class Entity Private mValidator as New EntityValidator() Readonly Property IsValid()[code]....
I'm concerned about .Validate(Me).I get no warnings or Code Analysis violations, but it just feels wrong. I get nervous about infinite recursion and garbage collection.
I create a form2.vb which have a report viewr and modifier set to public. In reportviewer properties i add the Report1.rdlc Now i want to pass the vlue in the textbox at report1.rdlc i use following steps and code to do it butnot sucessful yet i need ur guidelines first from menu click report ___ report parameter and set the parameter name like conparm. Then i frm2 load event i write following
I have created a Dictionary class (MyDictionary for the example). I am currently trying to pass MyDictionary into a function, filter it into a new instance of MyDictionary and pass this new instance into another method. When I am attempting to create the second instance from the filtered first instance of MyDictionary via Lambda Expressions and the ToDictionary Method, I am getting the following error:
Unable to cast object of type 'System.Collections.Generic.Dictionary`2[System.Int32,System.String]' to type 'MyDictionary'. I have simplified the example and recreated it in LINQPad and am getting the same error.
With the two lists (t1s and t2s), I want to display t1s in a DataGridView, and in one column show the T2 property as a comboBox column, which dropdown will show the t2s list such that a new list instance can be selected. T2 has a Name property that should be used for displaying it in the comboBoxColumn.
I'm able to display the dropdown, but remaining a few problems:
1. How to display the correct comboBox "selection" on "load"?
2. How to change the T2 child object instance when combobox selection is made?
3. This is a really basic problem, which suddenly happened and I just couldn't understand what I have changed; The code marked BLUE now just shows empty cells.. While the AutoGenerated columns do show values.. Shouldn't those "manual" columns work?
When you create a webpage in ASP.net, the codebase inherits System.Web.UI.Page Now when I extend the page object to check for SessionExpired for example, I create a new class and inherit from system.web.ui.page, and overwrite some functions. The problem then is that on each page, I have to replace system.web.ui.page with my custompage class. Is there a way to extend a class by adding methods or modifying its methods directly (e.g. add the sessionExpired check to System.Web.UI.Page) ?I'm using .NET 2.0
I know from .NET 3.5 onwards (or might be 3.0) we can use Exension Methods to add our own methods to any Type in the .NET Framework and this is very handy, but I'm wondering if it is possible to "extend" an Enum as well?
I would like to create a DataGridView that displays records that fill either 18 or 35 columns. I would like to avoid displaying all 35 columns for all records, instead showing the 17 extra columns on a second row for records that need them.How would I go about this? I'm guessing I need to create a new class that inherits from DataGridViewRow and override it's Paint or PaintCells method, but I have no experience with overriding Paint events, so I'm kind of lost after that.
