I have 3 similar functions, that only change based on numeric type:
<Extension()> _
Public Function ToNullableShort(ByVal str As String) As Short?
Dim intReturn As Short
[Code].....
I was trying to make a generic function out of this, but couldn't do it. How can I make a generic function that will take a specific T and make it a Nullable(of T)?
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 have a generic List(Of Customer). The customer class has a name, address, and phone number properties. I also have a property of another class that accepts a customer name array. I am able to do this by doing the following:
Dim names As String()
Dim i As Integer = 0
'customer.GetCustomers is a List(of Customer)
[Code]....
Is there a better way to convert this to a string array?
Consider a MyForm class that contains a shadowed implementation of Show(). It also contains a CreateForm() method, which accepts an instance of the form and calls the shadowed sub:
[Code]....
I'm having a problem converting a string of letters to a string of numbers. I've tried:
Dim A As String = ""
Dim strOutput As String = ""
Dim X As Integer = 0
[Code].....
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 the following VB.NET function, for example:
Public Function MyFunction (Of TData) (ByVal InParam As Integer) As TData
End Sub
How do I, in a function, determine if TData is a NULLable Type?
I have the following VB.NET function, for example:Public Function MyFunction (Of TData) (ByVal InParam As Integer) As TDataEnd Sub
View 5 RepliesScroll to the bottom, EDIT 19 onwards. See @Chris's comments also for good examples
[code]...
It's all gone quiet since Edit 19ish and @Chris reinforcing the issue with a good example (thank you Chris). I'll make the question a little easier (and attempt to tidy up all of the above), can anyone prove this is not an MS bug or similar? It seems to be something under the hood is not correctly wired up for VB.Net with regards to Nullable Structures and Events? However, all other cases using the Nullable Structures does appear to work?
I need to return an a generic list in the correct order for my project, and I'm getting InvalidCastException errors. Here is the code:
Dim lDt As List(Of Comment) = RemapCommentsForE1(so.CommentList). _
OrderBy(Function(x) x.CreateDate.Value). _
ThenBy(Function(x) x.Sequence). _
[code].....
I have encrypted a string to something like this:
1. Asak2$)kla1015QAXKFskfa332aSJ2(Ska@Skljcmcel3p.lq,aowpqaskla2@)Skx.:Pdm^),dfs;
what i want to is convert this string to something like this
2. JXK2LB AP2WXB S1P0XE ZXPA3H X1LAKW DOXPS3
both 1 & 2 the above strings are fictitious (i made them up to make my point clear)
I am trying to make a licensing system for my VB 2010 express application. (2) above will act as a serial key which can be derived from (1) which is an encrypted form of something unique of the client computer.
I will then confirm the (2) from the client.
I 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.
Write an overload for every numeric type or if possible constrain a generic extension method to just numeric types.
View 2 Repliesclass
eg: dim classobj = xyz("CLASS_NAME") ' where classname is a valid class name
and dynamically raising a known method of that class on that newly created object or class reference.
[code].....
I have a generic Class I'm using to hold information loaded from a database.I have a method which takes a DataRow as an argument, uses the object's known column name and extracts the data from the DataRow, such that:Dim loadData As T = CType(myDataRow("myColumnName"), T))works as my default assignment in most cases.Unfortunately, due to some horrifying design constraints, some of my columns may be null, and may also be taken from enumerations.This means that when <T> is Nullable(Of SomeEnumeration) the above code does not work because I can't cast 0 directly to SomeEnumeration.Zero.Is there some way to check whether <T> is Nullable(Of [Enum])? Or some way to write a method which allows Integers to be cast to Nullable(Of [Enum])?I feel like I'm forgetting something that would allow me to write one of the other of these, but my weak google-fu is turning up nothing.
EDIT: Okay, thanks to dasblinkenlight's answer below, I can detect when this circumstance is occurring, but what I need to do now is to take a type <T> which I know is Nullable(Of SomeClass), get a type reference to SomeClass and then create a new object of type Nullable(Of SomeClass) and assign that to LoadData.My problem was that I had a lot of difficulty in finding any function which would accept baseType as an actual Type.Parse accepted baseType as a parameter, I knew baseType was an [Enum] type because of dasblinkenlight's code, so I was, in this instance, able to code a solution. It's a solution which is very specific to my problem (i.e., T is Nullable(of SomeEnumeration)), but it's a solution nonetheless.
Im working on my first n-tier application. I am trying to serialize a structure and Im getting an error"Soap Serializer does not support serializing Generic Types : System.Nullable`1[System.DateTime]."Here is the structure that is being serialized
Namespace Structures
<Serializable()> _
Public Structure structAllergy
Public AllergyID As String
Public ProfileID As String
[code]....
The bold line is the line that is throwing the error.
I have a function that works great in C# that I'm converting to VB.Net. I'm having an issue converting the result set to a generic list in VB.net.
The code:
Public Function GetCategories() As List(Of Category)
Dim xmlDoc As XDocument = XDocument.Load("http://my_xml_api_url.com")
Dim categories = (From category In xmlDoc.Descendants("Table") _
Select New Category()).ToList(Of Category)()
Return categories
End Function
The error occurs when convertng the result via .ToList(Of Category)() The error:
Public Function ToList() As System.Collections.Generic.List(Of TSource)' defined in 'System.Linq.Enumerable' is not generic (or has no free type parameters) and so cannot have type arguments.
Category is a simple object I've created, stored in the App_Code directory.
I have the necessary "Imports System.Collections.Generic" reference in the file so I don't see why I can't convert the result set to a generic list.
I am trying to avoid every single function affecting my response time.therefore my question is using ToArray while converting generic list to array, does this take significant response time?should I use array directly while building my array within for each or working with list of and then at the endusing ToArray? any difference?
View 1 RepliesI have a Generic.List(Of ImportedVehicle) - ImportedVehicle being a simple class as below.There is an enum property which is marked as public.When I serialize to XML using an XMLSerializer, the enum's value is just set to it's default value (which is NotAllocated) and doesn't actually represent the value that is set in code.[code]
View 1 RepliesI wrote my own database handling code (actually, I write T4 text templating files that generate my database code for me) and part of it takes care of converting values from a database (as Objects) to the desired types.
I have been using this generic function successfully:
vb.net
Public Overridable Function ConvertType(Of T)(value As Object) As T
Try
Return If(value IsNot Nothing AndAlso value <> DBNull.Value, DirectCast(value, T), Nothing)
[Code]....
Simple enough, but it doesn't work... The return type of the function is (and must be) T, so I cannot return a Boolean because a Boolean cannot be converted to T!
Well... It can in this case, because I specifically check that T is Boolean, but the compiler doesn't know this so it doesn't allow me to return a Boolean. I cannot cast the boolean to T either.
I wrote my own database handling code (actually, I write T4 text templating files that generate my database code for me) and part of it takes care of converting values from a database (as Objects) to the desired types. I have been using this generic function successfully:
vb.net
Public Overridable Function ConvertType(Of T)(value As Object) As T
Try
[code].....
I am creating a 'generic input dialog': InputDialog(Of T).The idea is that I can create new instances of this dialog for different values of T. For example,I can create an InputDialog(Of String) and it displays a textbox.I create an InputDialog(Of Boolean) and it displays two radiobuttons (I could use a Checkbox, irrelevant).I create an InputDialog(Of Date) and it shows a DateTimePicker.
I do this by simply checking the type of T at run-time.In this way it is not really generic, as the dialog still has to know which type T is (which is usually not the case), but the generic is in the fact that the T can be multiple types that require a TextBox. For example, InputDialog(Of String), (Of Integer), (Of Single), (Of Double), etc, all simply display a TextBox (and it is validated later),so I still want to use generics as much as possible.Anyway, the result of the dialog is of course a property of type T. This property needs to return the value in the textbox, converted from string to T, OR the value in the DateTimePicker, converted from Date to T,OR the checked property of the 'Yes' radiobutton, converted from Boolean to T.In order to convert from any object to T I googled and found this
vb.net
Imports System.ComponentModel Public Class GenericTypeConverter Public Shared Function FromObject(Of T)(ByVal value As Object) As T Dim tc As TypeConverter = TypeDescriptor.GetConverter(GetType(T)) Return CType(tc.ConvertFrom(value), T) End Function End Class
I have to use this, I cannot simply CType a string to T since a String cannot be converted to any type T.So, my Result property looks like this at the moment:
vb.net
Public ReadOnly Property Result()[code].....
This actually works for Strings, Integers, Doubles, Singles, etc. I pass it the String in the textbox and it converts it to 'T'(note: T is then a String, Integer or Double!) just fine.So, it can convert a String to a String, Integer or Double without any problems (I am validating the text before using the Result property so it will always be a valid integer, double, etc).However, it does not work for a Boolean, nor for a DateTime. When I try that, it says "BooleanConverter cannot convert from System.Boolean" or "DateTimeConverter cannot convert from DateTime". I realize it is a bit of a strange thing, since the object already IS a Boolean or a Date(Time) so no conversion should be done at all, but this doesn't work in design-time because I need to return the objects as type T.I know that T will be Boolean when the value to be converted is a Boolean, and that T will be DateTime when the value to be converted is a DateTime, but the designer does not accept a simple CType. As I said, it does not accept this:
Return CType(rbYes.Checked, T)
because 'Boolean cannot be converted to T'.
However, I did find a way to make it work, but it seems like a complete hack... I can assign the boolean to an Object and then convert that using CType:
Dim obj As Object
obj = rbYes.Checked
Return CType(obj, T)
This works, it's accepted during design-time, and it works during run-time, but it seems very wrong... Is there no better way to handle this?
I am really trying to follow the DRY principle. I have a sub that looks like this?
Private Sub DoSupplyModel
OutputLine("ITEM SUMMARIES")
Dim ItemSumms As New SupplyModel.ItemSummaries(_currentSupplyModel, _excelRows)
ItemSumms.FillRows()
[Code]...
I have a class myClass. MyClass has a property myName. I have a generic list myList(of myClass). I have to check if value of myName in all myClass objects in myList is same and is equal to a string myString. I have created a method:
Private Function IsMatching(ByVal objMyClass As MyClass, ByVal strMyString As String) As Boolean
If objMyClass.MyName = strMyString Then
Return True
Else
Return False
End If
End Function
Now I want to use is TrueForAll method of Generic list. How can I use it ?
If there was No second Parameter in IsMatching method, I could have simply used
myList.TrueForAll(AddressOf IsMatching)
But since there is a parameter strMyString, I dont understand how can I use IsTrueForAll method. How can I use IsTrueForAll method in this scenario.
Currently my code has the following properties:
[Code]...
I have a problem with the VB.NET compiler failing to compile a class (in a separate C# assembly) which contains two overloads of a method with generic arguments. The equivalent code in C# compiles against the same assembly with no errors. Here are the two method signatures:
protected void SetValue<T>(T newValue, ref T oldValue)
protected void SetValue<T>(T? newValue, ref T? oldValue) where T : struct
Here is the code to three assemblies that demonstrate the problem. The first is the C# assembly with a Base class that implements the generic methods. The second is a C# class derived from Base and calls both overloads of SetValue correctly. The third is a VB class also derived from Base, but fails to compile with the following error message:
[Code]...
Am I doing something wrong in the VB code, or are C# & VB different when it comes to generic overload resolution? If I make the method arguments in Base non-generic then everything compiles correctly, but then I have to implement SetValue for every type that I wish to support.
After looking at this thread.>>
How to randomize the alphabet I have decided to make it into an extension method for a String and a List.
Note: Please see the following post if you are still using VB.Net 2002, 2003 or 2005
this code is for use with 2008 and later versions of VB.Net
String.Mix and also List.Mix I was trying to write a generic extension method for every Enumerable(Of T)
I settled on just doing it for a STRING
[Code]...
Getting this error message and I am not able to figure out why. Here is my code:
<asp:TextBox ID="searchParam" Width="250px" runat="server"></asp:TextBox><asp:button ID="btnSearch" runat="server" Text="Search" />
<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="getCOMDLs" TypeName="NewEmployee">
[Code]...
I wonder if this is not possible dim mystring as string="1" dim myint As Nullable(Of Integer) myint=0 myint=mystring It crashes on the last line why is that? mystring is already integer (1) , i dont have to cast using cint, i thought. option strict off- if this cause the problem
View 7 RepliesDim nullInt As Int32?
Console.WriteLine("1: " & nullInt) 'has no value
nullInt = If(False, Int32.Parse("12345"), Nothing)
Console.WriteLine("2: " & nullInt) 'has value 0?
nullInt = If(False, Nothing, Nothing)
Console.WriteLine("3: " & nullInt) 'has no value?
