I have a generic method where I want to do something special for Strings.
I've found DirectCast(DirectCast(value, Object), String) to get the String value (when I've already confirmed GetType(T) Is GetType(String)) and DirectCast(DirectCast(newvalue, Object), T) as mentioned in a number of answers to similar questions works.
But is there anything more elegant and is it performant?
In a tic tac toe game I'm working on I have 2 dictionaries (plyrPairs and cmptrPairs) In the program there is a procedure that is used numerous times. The procedure varies with the dictionary that it calls. I'd like declare a variable in a sub procedure that will represent these two different dictionaries. Here is what I have:
Here are the two enumerations:
vb.net
' Assign values to player pairs enumeration
Private Enum plyrPairsList
empty = 0
[Code].....
I'm tyring to pass a variable data type to a template class. Something like this:
frmExample = New LookupForm(Of Models.MyClass) 'Works fine
Dim SelectedType As Type = InstanceOfMyClass.GetType() 'Works fine
frmExample = New LookupForm(Of SelectedType) 'Ba-bow!
frmExample = New LookupForm(Of InstanceOfMyClass.GetType()) 'Ba-bow!
[Code].....
I'm assuming it's something to do with the template being processed at compile time but even if I'm off the mark there, it wouldn't solve my problem anyway. I can't find any relevant information on using Reflection to instance template classes either.
(How) can I create an instance of a dynamically typed repository at runtime?
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.
I'm strictly looking for a language conversion here of this:List<?> I already have a work around I'm just surprised that I can't find the vb.net equivalent of a variable type of a "raw" generic list that takes a wild card.Java's mechanism here enables you to reference a list regardless of what T is.Java even enables you to go further and do things like:
List<? extends Number>
List<? super Double>I tried:
List(Of )
and that did not work. That only seems to work inside the GetType function.
Consider:
Public MustInherit Class Column
Public ReadOnly Property ReturnSomethingUseful() As Object
Get
'return something useful
[code]....
But this gives the following error:
Public Overrides Function ParseValue(sValue As String) As Boolean'
cannot override 'Public Overridable Function ParseValue(sValue As String) As Object'
because they differ by their return types.
I accept that you can't do this, but I'd like to be able to preserve the semantics of what I'm. trying to do, which is to have an untyped version that deals with Object, but a typed version in derived classes that knows about the specific type T.
I have a Journal that records entries for different types: Journal(Of ParentT)
[Code]....
I am trying to construct a generic interface class with generic functions. My goal was to use this to implement multiple worker classes for database interaction that have the same basic functionality. Each class will deal with different object for example, category, product or supplier but unless the the functions in the interface are generic that this won't work.This is the interface code that I have but I don't know if I have done it correctly. [code]
View 2 RepliesI am trying to create a list of a generic type in vb.net 2.0 framework.
This is the generic type definition:
Public Class GenericParamMap(Of T)
Public Sub New(ByVal pParamName As String, ByVal pPropValue As T)
mParamName = pParamName
[Code]....
The compiler does not allow a "T" in the method's parameter because it's not defined, but I'm not sure how or where to define it. I thought it was okay to have a generic method definition.
I am trying to write a generic method, to avoid code duplication, which will create or activate a Form as an MDI children, based on its type. But I have to lines in error (see comments).
[Code]...
Dim x = GetType(List(Of )) 'valid statement
Dim list As New List(Of String)
Now I want to see if list is a List(Of T) variable: Dim isList = TypeOf list Is List(Of ) On the last line I get a compile error: "Type Expected". Is there any cheap-performance TypeOf operator alternative for generics?
If i have an object that implements an interface (and don't know the exact object) i can call a sub (DoSomething) by going:
vb
Dim iObj = trycast(something, iInterface)
if iObj isnot nothing then
iObj.DoSomething()
end if
How can I do this for a Generic? such as...
vb
Public Class TestClass(of T)
Public sub DoSomething()
....
end class
I have been using a pretty slick generic invoke method for UI updating from background threads. I forget where I copied it from (converted it to VB.NET from C#), but here it is: Public Sub InvokeControl(Of T As Control)(ByVal Control As t, ByVal Action As Action(Of t))
[Code]....
I can do this without problem.
Class A
End Class
Class B : Inherit A
End Class
Dim Obj1 As A = New B
I am getting the error:"Range variable 'sender' hides a variable in an enclosing block or a range variable previously defined in the query expression."for this
Imports System.Data.SqlClient
Imports System.Linq
Public Class Form1
[code]....
I can select any other item from the table without the error. "sender" has the same properties as "receiver" in the SQL table.
I receive the error -
[Code]...
Public Class Form1
Dim x, c, number(0 To 19) As Integer
Dim s As Integer
[CODE]...
The variables in the brackets [example] do not actually have brackets in them in the original code. These are where the issues are. For both variables, it says, "The type for variable [variable] will not be inferred because it is bound to a field in an enclosing scope. Either change the name of [variable], or use the fully qualified name (for example, 'Me.[variable]' or 'MyBase.[variable]')." Now, I'm not entirely sure if this is a stupid question or not, as I'm used to VB '98 because that's what we use in my programming class at High School. let me know why this won't work.
-Note: The intention of this program is to continually loop the generation of numbers for this list until I tell it to stop. Button1 ends the program, Button2 generates the list one time only, Button3 is supposed to loop the generation of the list, and Button4 is supposed to end the loop, but not the program.
Say that i have the following code that parse about 20k records from the DB.
Code #1
vb.net While reader.Read()
list.Add(If(Integer.TryParse(reader(0).ToString, 0), Integer.Parse(reader(0).ToString), 0))
End While
And then another code which does the very same thing but it seems to be a little cleaner.
Code #2
vb.net While reader.Read()
Dim storeowner As Integer = 0
Integer.TryParse(reader(0).ToString, storeowner)
list.Add(storeowner)
End While
This is what i am confused about; does the compiler creates a new variable automatically when i use the if statement without strictly declared variable? What approach is better in sense of performance?
I am looking for a good resource on variable naming conventions to illustrate variable type and where variables are declared. So I will have public variables, Private variables, private or local variables. I also may want to declare variables with the same name in different class code (i.e. in the code behind different forms). I am assuming good coding would dicatate a prefix for declaration location.
View 4 Repliesi have this error in the line of with xl.active......Object variable or With block variable not set.
Dim xl As Object
xl = CreateObject("Excel.Application")
With xl.ActiveSheet.QueryTables.Add(Connection:= _
"TEXT;C:Documents and SettingsUserDesktop429MEDICA2.TXT", _ Destination:=xl.Range("$A$1"))
[code]....
Now I have the need to get a current value from a bindingsource in a property of a user control.In a previous thread I had tracked down the "Object variable or With block variable not set" to the return in the Get block of a property. At the time I was only using the Set so I just commented out the offending code until I needed it.
[Code]...
The error does not occur during a system compile, only upon saving the container object of the user control. As I said the Set works correctly, only the Get causes the error.I would like to know what I am missing/misunderstanding and am open to other suggestions of handling retrieving the current value of a bindingsource in a user control.
Using Visual Basic 2008 Express. I need to pass a variable to another form. Or else make the variable visible to both forms.
View 4 RepliesI am using vb2008.net express,I test vs2005term it work, can any tell me what is the input variable and output variable of this terminal?how to catch the input and output variable to a textbox1 for sending and a textbox2 for receiving when I press send button? is that possible?
View 1 RepliesI have the following code that I am using to parse out a test file. I am getting variable conversion error in Sub Main() when I assign file = Read(). The return value of Read() is a TextFieldParser type. How do I assign the proper variable type to "file" so I can write the output to a text file?
Function Read()
Using MyReader As New FileIO.TextFieldParser("C:UsersColinDesktopParse_Me.txt")
Dim currentRow As String
[Code].....
I have the following code but I get blue squiggly line in cnn and when i point my mouse pointer on it i see this message "Variable 'cnn' hides a variable in an enclosing block"
Private Sub BtnLockUnlock_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnLockUnlock.Click
Dim IsLocked As Boolean = FpSpread1.ActiveSheet.DefaultStyle.Locked
[code].....
I have the following code passing a dataView variable to a function and I am getting the following warning:"Variable 'cl' is passed by reference before it has been assigned a value. A null reference exception could result at runtime."
Function Editclass()
Dim cl As DataView
Bindclass (SqlConnection2, cl)
[code].....
i had a class called Tag with a structure like:
public class Tag
private _members
public properties
public shared database_methods
end class
this class was tailored for mysql database. i'm currently adding access 2007 support so i split tag into tag and tagdata with structures like:
[Code]...
I'm having trouble tracking down what is wrong and causing the above error. This only occurs when saving the design view in VS 2012. The code builds and runs fine.Full error text:Code generation for property 'CompanyValue' failed. Error was: 'Property accessor 'CompanyValue' on object 'ContactViewUC1' threw the following exception: 'Object variable or With block variable not set."
CompanyValue definition in ContactViewUC:
Public Property CompanyValue
Get
[code].....
Been getting this error with my program. Using framework 2.0
[Code]...
I'm trying to enter automatically todays date in a number of records in the Table 'Applications' into the field 'Date_refund_request'.
However it is giving me the error 'object variable or withblock variable not set' in the line "Set rs = db.OpenRecordset(strSQL, dbOpenDynaset)".
The code is as follows:
Private Sub Command16_Click()
On Error GoTo Err_Command16_Click
Dim db As DAO.Database
[Code].....