Okay, so I have a Generic IList of custom objects that I want to use as a datasource for a repeater.
Dim productRows As IList(Of MyCustomObject)()
'fill list with data
rptResults.DataSource = productRows
[code]......
I am creating a generic class that is Implementing IList(Of T) which requires that I implement the GetEnumorator of both IEnumerable(Of T) and IEnumerable. When looking at the members of IList(Of T) I see only one GetEnumorator function, yet it implements IEnumerable(Of T) and IEnumerable. How can I use one function to implement both interfaces when the function definitions only vary by return type?
View 8 RepliesI have a piece of code that does an action to any collection that implements generic.IList<T>However to do this it needs to get the type <T> of the generic list.e.g. If I pass in a variable of type Generic.List(Form) then in my code I need to get the fact that the list is made of Forms. To add complexity the list may be empty (So you can't just look at Item(0).GetType)
View 6 RepliesPublic Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T)Return DirectCast(data, GenericType(Of T))End Function
The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T?
I'm trying to use a variable that is simply a list of a list of strings.I've declared it as follows:
Dim iRows As New List(Of List(Of String))
Then I'm trying to pass it as a parameter to another method and I've defined the method as follows:
Public Sub Import(ByVal Rows As IList(Of IList(Of String)))
For Each Row As IList(Of String) In Rows
ImportRow(Row)[code]....
Unfortunately, when I try to run that code I get the following error where it tries to pass my variable to my method.
System.InvalidCastException was unhandled by user code
Message="Unable to cast object of type 'System.Collections.Generic.List1[System.Collections.Generic.List1[System.String]]' to type 'System.Collections.Generic.IList1[System.Collections.Generic.IList1[System.String]]'."
When I change the method definition to use the types rather than the interfaces as follows, it works.
Public Sub Import(ByVal Rows As List(Of List(Of String)))
For Each Row As IList(Of String) In Rows
ImportRow(Row)[code]....
So, is it not possible to use generics with interfaces in this way? It works fine as long as I'm not nesting them.
I am declaring an IList:
Dim OrigVendors as IList
OrigVendors = new List( of IVendors)
I populate the OrigVendors variable and what I want to do is find all the objects that have the ID I am looking for. Then I need to update a property on that object for only the ones found. Is this do able with an IList or do I need to use some other type of collection? I am using VB.net.
I'm new to generics and am having some issues when using with interfaces.I'm developing with VS2008 - .NET 3.5 Ultimately, I'd like to create an interface that inherits the IList(Of T) interface and add a function definition to the derived interface that adds a new element of type T to the list and returns the index of the newly added item.
I have everything figured out but am stuck on a casting issue. If I execute the following line of code at runtime:CType(New clsObjectFactoryList(Of clsIDNamePair), ifObjectFactoryList(Of ifIDNamePair))
I have an object that inherits from an interface. I can create and return the following:
Dim o As IRequest
o = New Request
Return o
This works fine. Now I want to return a List(Of Requests), so I try the following:
Dim o As List(Of IRequest)
o = New List(Of Request)
Return o
The error below is being given on o = New List(Of Request)
System.Collections.Generic.List(Of MyObjects.Request)' cannot be converted to System.Collections.Generic.List(Of MyInterfaces.IRequest)'.Consider using 'System.Collections.Generic.IEnumerable(Of MyInterfaces.IRequest)'
i have the following code which walks through an Excel file and this works fine note that the following line does work well (folder is being set earlier in the code)
[Code]...
I've got a project called Service.Inside the project, i've got 2 windows classes.ClassA is the main windows class which opens up when I run the program.On ClassA, I've got a button which, when I click it, opens up ClassB which is the other windows class. Inside the button's eventhandler (click), I've got a string which contains the name of ClassB's class ie "ClassB". I will probably get this from a table. Is it possible to initiate the object ClassB without using if statments to check what the type of object is. In the code below, i've managed to create a o of type object, but i need to new it with the ClassB
vb.net Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
[Code]...
I have been trying for 2 weeks now to get this program to work.I am using VBasic and MS Access 2007 in conjuntion with a software application.the Database has 2 fields
1) Text
2) OLE Object (.jpg)
when I try to preview the data inside the DataSet I can only get the text to come threw, but that isn't the problem...the problem is binding the data to a datasource and displaying the information.I cannot get the database to display the information in FIELD 2
I have an object, called 'PERSON' This person object has a title, firstName & Surname property as well as many other which are at the moment irrelevant. It also has a read only property called Fullname which concatenates the two or three parameters mentioned above depending on an optional parameter 'withTitles' passed over when you call PERSON.FULLNAME
PERSON.FULLNAME(true) <- Will add titles if there are any
PERSON.FULLNAME(false) <- Will give the name without the title
Public ReadOnly Property FullName(Optional ByVal withTitle As Boolean = False) As String
[Code]...
I get an error: PERSON does not contain a property of 'FullName'. If I change this to any other property that does not take a parameter it works as expected. Now I'm guessing that the binding procedure can't handle optional or mandatory parameters for object properties, is this right? Is there a better way to do it? I thought about looping through the collection to add them manually but that kinda defeats the object of DataBinding!
I have two custom objects.On of them inherits the other one, appends few more properties and methods, ovverides some other.When I try to cast the Parnet Object to Child I receive an error that it could`nt be done.
View 1 RepliesI have a function that returns a list of account numbers as an Arraylist. I am trying to use each account as a command parameter in another sub routine to get more data about each account number. This only returns the data for the last account number in the arraylist. I need to use each account number, call the database, get the additional information and store ALL of the data into a Gridview (databind). Example: If I had 3 account numbers in my arraylist return 3 rows of data to the gridview. I am struggling with how to get ALL of the information for each value (account number) in the Arraylist. Can someone point me in the right direction?? I think this can be done but I am not certain if my approach is correct or not. Perhaps I need to create datatables that contain the additional information for each value passed via the arraylist.
Private Function ReturnMultAccts(ByVal strAcct) As ArrayList
Dim acctsDetail As New ArrayList
Dim dsn As String = Configurati
[code].....
Here is a test program I wrote to explore a facet of object casting ...
Module Module1
Sub Main()
Dim class1 As MyBaseClass = New MyBaseClass()
Dim class2 As MyInheritedClass = New MyInheritedClass()
Dim class3 As MyBaseClass = Nothing
[Code] .....
The problem comes with the TryCast statement on class3. My intention is that class3 remains as a baseclass, but when the TryCast is applied, class3 morphs itself into an Inherited class which is not what I wanted. So is there a gap in my OOP/VB.NET knowledge and this action is legitimate or should class3 still be regarded as a base class?
I was just wondering if it is possible to apply an attribute to a property within a business object (MyBusinessObject) such that after the DataSource of a grid is set to a List(Of MyBusinessObject), the visible property of the column will automatically be false. For example:
myGrid.DataSource = New List(Of MyBusinessObject)
Public Class MyBusinessObject
[code]....
Unable to cast object of type 'System.Windows.Forms.ToolStripButton' to type 'System.Windows.Forms.ToolStripMenuItem'.This is the error, when I click on the bookmark(When I add the bookmark, It's a non-clickable menu item; the next time i debug it, it becomes a clickable url(button)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
...
Call minginimi()
End Sub
[code]....
I've got a piece of code in a project (MyProject) that contains early bound object from a referenced assembly (We'll call it CommonAssembly):
Dim myObject As CommonAssembly.MyEarlyBoundType
now I have another assembly that is dynamically loaded because it is not present in all projects:
Dim myLateBoundObject As Object = AppDomain.CurrentDomain.CreateInstanceAndUnwrap("Utils", "Utils.MyLateBoundType")
MyLateBoundType derives from CommonAssembly.MyEarlyBoundType, and I want to cast myObject to myLateBoundObject and then programmatically invoke the additional
[Code].....
I have relations between two object, but is there a way to load an object when calling a property? I tought about a generic class above a object, where the value is set. On request of the property i can load a value out of the database at that moment.. This
can work i think but the problem is that i must call a sub property of Reference(of TObject) like pObject.Value to access the ObjectB.
So my question is, is there a way to execute code before loading a property (like with a base class or something else) or is it possible to set a default output to ObjectB for Reference(Of ObjectB) so i don`t have to access pObject.Value to walk trought ObjectB?
[Code]....
I have a class which extends HashSet(Of T).I am trying to evaluate some custom properties of this HashSet during execution and make decisions based on those values.
During debugging, I am pausing execution and adding a Watch on my instance of this HashSet.
The Watch only provides me with a view of the Count of the HashSet and the objects contained by the HashSet.How can I get the Watch to show me the other properties of the HashSet?
I have a routine that accepts a List of Objects, a property name and a value to search for and simply returns whether or not it found it.The code I have hangs up at the For loop in the findit routine.[code]
View 4 Repliesgiven 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]
View 1 Repliesi've got a generic class for xml serialization and deserialization.
Public Class clsXMLHandler(Of T)
Public Sub serializeFromObject(ByVal filePath As String, ByVal [object] As T)
Dim creater As New FileStream(filePath, FileMode.Create)
Dim xml As New XmlSerializer([object].GetType)
xml.Serialize(creater, [object])
[Code]...
Dim tenItem = From t In _InvalidFeeList _
From i In ItemCount _
Where t.FeeCode <> i.FeeCode _
[Code]....
I am getting "Can not convert to System.generic.list" error. I look all over for this error and it seem like my code should work for example here
edit: I think i should explain what I'm trying to do here. I want to compare two object list and select the object from the InvalidFeeList if the FeeCode is not equal to the object in ItemCount FeeCode and take the first 10 objects from the InvalidFeeList.
I'm using EF 4.3.1 in VS 2010 (.Net 4.0) to load a number of reference tables from a database in order to bind them to controls in a WinForms app.At form load, I'm pre-fetching the data so that it's stored locally, and I'm creating a dictionary of BindingSource objects that I can use to bind the local data to the controls.The intent is to minimize the impact of the EF's self validation on a cold query in order to load forms faster and improve UI responsiveness.I've written code to create and fetch the BindingSource object for a given DbSet collection as follows:
Private _dictBindings As New Dictionary(Of String, BindingSource)
Private Sub ValidateBinding(Of T As Class)(ByRef DbCollection As DbSet(Of T))
Dim strClassName As String = DbCollection.[GetType]().GetGenericArguments(0).Name
If Not _dictBindings.ContainsKey(strClassName) Then[code].....
However, I'd like to call ValidateBinding on all DbSet collections in the Model on startup, and I'd like to use reflection to iterate through the available collections in the context because we're currently loading 66 tables and could add more later.I've written the following code:
For Each propSet As PropertyInfo In Db.GetType.GetProperties(BindingFlags.Instance Or BindingFlags.Public).Where(Function(P) P.PropertyType.IsGenericType)
ValidateBinding(propSet.GetValue(Db, Nothing))
Next
but it won't work as propSet.GetValue() returns an Object instead of DbSet(of T).I also can't cast the object to a DbSet of the appropriate type, even though I know the type through reflection.I don't have access to the C# Dynamic type,and I know it's a pain to mix generics with reflection, but is there a solution for which I can pass in a reflected DbSet to my functions?Perhaps something using Method.Invoke?
We have migrated our Vb6 application to VB.NET using a third party tool. Now we are in a process of Refactoring and introducing object oriented concepts in the application.
In VB6, we were using structures in many places. As a part of introducing object oriented programming,
1. is it a good idea of changing all Structures to Classes? or Is there a concept of "Generic Structure" similar to Generic collections, Generic classes?
2. Can some one guide me any source containing guide lines or best practices for applications that are migrated to VB.NET from VB6 and implementing object oriented programmaing.
How do I use the IList(Of T).Max function in my example below?
Dim myList as IList(Of Integer)
For x = 1 to 10
myList.add(x)
Next
'Error: 'Max' is not a member of 'System.Collections.Generic.IList(Of Integer)'
MsgBox(myList.Max())
i have to develop API in .Net 4.0 which can be used in VB 6.0,i know how to use this and currently i am using my this API in VB successfully.but Stuck at one place,i have collection class and i have to expose it to VB with having functionality of List class of .Net.[code]i know that generic is not supported in VB, but i think with this declaration in VB 6.0 it creates interface class for class B as IList.but in VB using object creation of class B it doesn't provides me members of LIST in intellesense like (Add,Remove of List Class)
View 2 RepliesHow could I add ObjectCollection items to an IList(Of SomeType)?I have tried with:
For Each obj As SomeType In listBox.Items 'ObjectCollection MyObject.ItProperty.Add(obj) 'IList Next
is it possible to add multiple strings per item in a Ilist?If so can someone point me in the right direction? I've looked on the msdn and can only find examples on how to add one string per item
View 16 Replies