Make A Shared Function Generic?
Feb 16, 2011
I can create classes that use generics, however I was wondering if it is possible to apply this to a shared method rather than rely on the caller casting to the correct type.This is the method:
Public Shared Function DeserializeObject(ByVal serializedXml As String, ByVal givenType As System.Type) As Object
Dim serializer As New XmlSerializer(givenType)
Return serializer.Deserialize(New IO.StringReader(serializedXml))
End Function
I'm pretty sure this can't be done, but thought I'd check (if so Extra points will be awarded if someone can technically explain why the compiler can't do this)..
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Sep 16, 2011
I have an abstract class in VB.NET. I want all classes that inherit from this class to return whatever value makes sense. For example, it could be an Decimal, Integer, String. How can I delcare the function in the abstract base class to allow for this? Is this even possible?
[Code]...
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Apr 29, 2010
Currently I have written a function to deserialize XML as seen below.How do I change it so I don't have to replace the type every time I want to serialize another object type ? The current object type is cToolConfig. How do I make this function generic ?
Public Shared Function DeserializeFromXML(ByRef strFileNameAndPath As String) As XMLhandler.XMLserialization.cToolConfig
Dim deserializer As New System.Xml.Serialization.XmlSerializer(GetType(cToolConfig))
Dim srEncodingReader As IO.StreamReader = New IO.StreamReader(strFileNameAndPath, System.Text.Encoding.UTF8)
Dim ThisFacility As cToolConfig
[code]....
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Jan 9, 2012
i would like to have a shared function in a separate class file to address the form location . but i dont know how can i get this to work. if i use this below code in my form its working . but i cannot move this to a class file.
Shared Sub Formlocation()
Me.StartPosition = FormStartPosition.Manual
Me.Location = Screen.GetWorkingArea(Me).Location
End Sub
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Jan 28, 2010
I have created a Interface and a couple classes that implement this Interface. I am in the process of developing a Shared Class that utilizes the functions that each of the individual classes have, due to the interface implementation.What i need to know is how do i develop this Shared Class so that way each of the methods within it are restricted to a single data type. This single data type needs to be restricted to any class that has implemented the Interface.
Some examples:
Public Interface IVector(Of T)
Sub Add(ByVal v2 as T)
[code]....
As you can see it would allow me to develop one form, since i have standardized the required Subs/Functions for any class the implements the IVector interface. As i am still in developement, i was wondering if my current understanding of the method generics is correct in its current form or what i would have to do to make the Generic Shared Class work in the fashion that i am looking for in the example implementation.
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Nov 4, 2011
I have a bunch of classes that all contain a Shared ReadOnly Dictionary. If I want to access that Dictionary when the class is a generic type (such as when I have a wrapper function that takes T as an interface that all of these classes implement), what's the way to do it?
I want to do something like GetType(T).GetMember("Dict"), but that will return a MemberInfo type, and that cannot be cast to a Dictionary of my defined type(s). For calling functions this way, one can use a delegate + CreateDelegate + GetMethod. But there doesn't seem to be an equivalent Create*for GetMember stuff. Or am I missing something?
If I plug the GetMember call into the immediate window, and then use a subscript as if it is an array, then the debug output says I am getting a Dictionary back. But if I use that same approach in the actual function that I am trying to write, then I get an error about System.Reflection.MemberInfo cannot be converted to Dictionary(X, Y)
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Jan 27, 2010
I have an interface that i have declared some of the basic internal functions, subs, properties, etc. This interface is then implemented into 3 pre-defined classes. These classes are end-use classes so they dont get derived or inherited elsewhere. I am trying to create a generic shared class that can operate on each of these 3 predefined classes and potentially more as long as they implement the interface.
[Code]...
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Mar 1, 2011
i have a function that i have in my data access class now i want to access it then declare and assign parameters and then insert data into database?
'1
'the function
Public Shared Function InsertNewRecord(ByVal myStoredProcedure As String) As Boolean
Dim conn As New SqlConnection
[code]....
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May 31, 2011
Anyone want to try converting this to VB?
[Code]...
It is supposed to sort any type of object. Taken from here
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Jun 2, 2010
Question: I want to call a generic function, defined as:
Public Shared Function DeserializeFromXML(Of T)(Optional ByRef strFileNameAndPath As String = Nothing) As T
Now when I call it, I wanted to do it with any of the variants below:
Dim x As New XMLserialization.cConfiguration
x = XMLserialization.XMLserializeLDAPconfig.DeserializeFromXML(Of x)()
x = XMLserialization.XMLserializeLDAPconfig.DeserializeFromXML(GetType(x))()
x = XMLserialization.XMLserializeLDAPconfig.DeserializeFromXML(Of GetType(x))()
But it doesn't work.I find it very annoying and unreadable having to type
x = XMLserialization.XMLserializeLDAPconfig.DeserializeFromXML(Of XMLserialization.cConfiguration)()
Is there a way to call a generic function by getting the type from the instance ?
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Jun 7, 2012
I have a grid view with a lot of columns, all need to be sorted on. I have seen a few snippets out there, but I cannot get any of them to work with my example. Here is what I have so far.
Protected Sub gvSearch_OnSorting(ByVal sender As Object, _
ByVal e As GridViewSortEventArgs)
If Not Session("sort") Is Nothing Then
[code].....
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May 31, 2009
i am beginner about general programming. Please give me basic shared functions .
I only know few functions such as : Public Shared Function lon(ByVal a As Integer, ByVal c As Integer) As String Public Shared Sub trung()
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Jan 24, 2011
VB.NET 2010, .NET 4. I am working on an application for controlling an industrial machine composed of many devices attached to the computer. Most if it is reasonable straight forward, but I'm having trouble thinking about the RS-232 devices. One of the RS-232 devices is a fancy power supply with many functions. The ones that are relevant right now are voltage read, voltage write, current read, and current write. The design pattern I'm trying to implement is one in which each attached device is represented by an object that has methods for reading/writing etc and properties for things like COM port etc.
For this power supply, clearly the Port reference should be shared among the instances, so I have a base class (say, PowerSupply) with a Protected Shared Property Port As IO.Ports.SerialPort. Then I have a couple classes that inherit from this class, PowerSupplyVoltage and PowerSupplyCurrent that each define read/write methods and properties for holding the last read/written values. My issue is in parsing the response from the power supply using the Port.DataRecieved event on the shared SerialPort object. The protocol the power supply uses specifies what data it's sending in each response packet.
So, basically, it might say something equivalent to "The voltage is 100V" or "The current is 1A" or "The voltage has been set to 150V" etc. I'm trying to parse this in a shared function. Only during the parsing process would I determine which instance's read/written value to update. I can't access the read/written value properties of the instances from within the shared function. The best I could think of is creating some kind of PowerSupplyCommunicator object that would maintain references to PowerSupplyVoltage and PowerSupplyCurrent instances along with the shared Port and DataRecievedHandler functions.
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Dec 30, 2009
how I can dynamically load a control inside of a shared/static function?The function itself is inside of a mustinherit/abstract class.(It's an ASP.NET project in VB) I want to do something like this:[code]I'm getting "Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class.",but I don't understand this error.I understand what it means, I just don't understand why calling LoadControl isn't seen by the compiler as being an explicit instance of the class. What's not explicit about using LoadControl to create a new control from a file? I tried creating a new user control and initializing it, then setting it to a different control with LoadControl to no avail.I also don't want to do a DirectCast because I'm trying to put this in a shared, mustinheret (abstract) class, which therefore doesn't have an .aspx file to write in a <%@ Reference Control="~/SomeControlPath.ascx" %>, so the class name is unavailable.What I'm trying to do is write a static function that takes some value and returns a control based only on that control's source file location.The end result is a user-modifiable list of controls.They get a column of controls that they freely add, remove, or reorder based on a static list of available child controls that I specify.
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Aug 6, 2009
I made the changes from this:
[code]...
to this:(the 'End Function' says "Function 'GetFolderPath' doesn't return a value on all code paths. A null reference exception could occur at run time when the result is used."
[code]...
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Mar 29, 2010
xplain to me or give me an example of using a select case in a shared function
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Jan 27, 2009
What's the advantage of declaring a function as "Shared"? I've noticed that it doesn't require you to instantiate an object to use the method when it declared as "Shared". Is that the only upside?
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Oct 12, 2011
written a generic "LaunchForm" function? For all the menu items I have that open a form, I would like to write one function that will launch the form as opposed to writing the same code several times.
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Oct 14, 2010
I have created a couple of simple functions in VB.NET that simply return a control of a certain type that I already know, such as HtmlInputHidden, Label, etc. That means that each of the functions is created only for that special purpose. What I'd like to do is combine all those functions into one function using generics. The common things shared by each of the functions is a control Id and a control type.What I have got so far is:
Public Function GetControl(Of T)(ByVal ctrlId As String) As T
Dim ctrl As Control = Me.FindControl(ctrlId)
If (Not ctrl Is Nothing) Then
[code]....
But the line " GetControl = CType(ctrl, T)" is giving me a compile error:
Value of type 'System.Web.UI.Control' cannot be converted to 'T'
This is in .NET Framework 2.0.
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Apr 1, 2009
I am attempting to create a generic function that the students in my introductory VB .NET course can use to search a single dimension array of a structure.[code]...
My question is: Is there a way to reference the individual structure fields in the array from inside the function? I was trying to make it generic so that the student could simply pass their array into the function - their structure may be named differently than mine and the field names may be different.
I suspect there are other ways to deal with this situation, but I was trying to keep it to just a simple single-dimension array of a structure. I don't think it is possible to do what I want, but I wondered what others thought.
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Aug 24, 2010
I am trying to write a generic function that will check each database parameter to see if it is null, and if so, return DBNull; if not, return the object.So here is my function:
Public Shared Function CheckForNull(ByVal obj As Object) As Object
If obj <> Nothing Then Return obj Else Return DBNull.Value
End Function
[code].....
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Sep 2, 2009
I must be doing something wrong here (because really, what are the chances of me tripping over another bug in the Vb.net compiler?)I have a static generic function in .net 2.0 Vb code, I thought it was time to "upgrade" it to be an extension method, but the compiler complains with Extension method 'AddIfUnqiue' has type constraints that can never be satisfied.
Here's a trivial example that displays the same problem. The old static version (which works fine) followed by the extension method
Public Class MyStaticClass
Public Shared Sub AddIfUnqiue(Of T, L As {List(Of T)})(ByVal this As L, ByVal item As T)
If this.IndexOf(item) < 0 Then
[code].....
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Oct 26, 2011
My question here is, what are the negative effects of using a generic function such as this? Calling this function does work, and in a test console module, it compiles perfectly fine. I do know this is not a strongly typed function, and is %100 bad practice. But it works perfectly. The purpose of a function like this, would be to handle string input that needs to be inserted in a particular format depending on the type. I also read some other questions on this here on stackoverflow, and suggestions pointed to using (Of T) functions, and variations like that. Why not do it this way? or is there another simple way of accomplishing this without creating a whole nothing class or larger amounts of code.[code]
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Jan 18, 2011
I like to turn Option Strict On I cant figure out how to write the generic version of this function?
Public
Shared
Sub UpdateItem(ByRef
oldValue As
[code]....
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Mar 1, 2011
[Code]...
i have a function that i have in my data access class now i want to access it then declare and assign parameters and then insert data into database.
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Aug 20, 2010
I get this error: Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class.
Partial Class _Default
Inherits System.Web.UI.Page
<WebMethod()> _
[Code]....
I know it has something to do with the fact that the first function is shared and the second function should probably be Public as well but I don't fully understand the reason behind it. Probably not relevant but I'm calling the web method from some javascript.
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Jan 24, 2012
I have as sub that is triggered from the file system watcher when the new file is created in spec. directory.I need to call some function to do something with that file. [code]
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May 11, 2012
i created a dll file using vb.net then it has a shared function that will execute a stored procedure of mysql but my code is something long and when accessing it, it has a big risk that it can produce an error if there is an incorrect string input, i am asking an advice how i can make it much better or can point me something much better than my code as my reference.here is my codefirst i created a function named mysqlParamDatatype wiith 1 parameter, this function will detect the mysqldatatype of the mysql sproc parameter so it can pass the value with the correct datatype. but it is to long.
Shared Function mysqlParamDataType(ByVal i As Integer) As MySqlDbType
If i = 1 Then
Return MySqlDbType.Binary
[code].....
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Jan 13, 2011
I would like to write a generic function that would search a List(Of T) for all elements of type TFilter and return a List(Of TFilter) which comprises those elements.
I've tried this:
Public Function FilterList(Of T, TFilter)(ByVal ListToFilter As List(Of T)) As List(Of TFilter)
Return ListToFilter.FindAll(Function(z) z.GetType.Equals(GetType(TFilter))).ConvertAll(New Converter(Of T, TFilter)(Function(z) CType(z, TFilter)))
End Function
But, it gives the following error:
Value of type 'T' cannot be converted to 'TFilter'.
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Jun 4, 2012
What's the best way to handle this situation: I have this generic function
Function FieldValue(Of T)(row As DataRow,fieldName As String) As T
Return If(row.IsNull(fieldName),Nothing,CType(row(fieldName),T))
End Function
In the special case where the field value is null and T is String, I want to return String.Empty instead of Nothing.
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