I have two class like this[code]...
The red code does not works. How do I get the type of data to declare, for example, a Specific Instance(Of integer) if Data is integer, and also Specific (of SomeClass) if Data is SomeClass?
D is a dictionary whose entry values are of Type T..What I'm attempting to do is have a delegate like "Serializer" below that I can invoke on an instance of T, such as "Entry.Value" below.Please see the "return Entry..." line below for my wishful thinking.[code]
View 2 RepliesI 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]...
I'm compiling a VB.Net 2.0 app (created in VS2008) using msbuild, and now I've added a generic return type, it's giving me the following:
Warning: Type library exporter encountered a generic type instance in a signature. Generic code may not be exported to COM.
Having just spent ages removing all of the previous warnings, I don't really want to add a new one. Any idea how to get rid of it (aside from not using generics)?I don't know what details I'd put in the attribute, or what number to put in the project-level ignore list.
I have a class C(Of T). I want to determine if some given value has type C, regardless of what T is. For example, I might want to determine if a value is a strongly-typed list, regardless what type of items the list stores. I just need to know how to do it in VB.net. In Java the syntax is like this:
var result = obj instance of Gen2<?>;
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?
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 have tried to write:
Event EventName(Of T)()
But Visual Studio tells me that "Type parameters cannot be specified on this declaration."
Is such a declaration possible or will I have to put T as a regular argument?
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.
I declare my dates as the following in my code:
Dim DeliveryDate as Date
But i am now trying to declare time however i keep getting an error because i cannot get the type correct. I tried the following but get the following error: "Conversion from type 'Timespan' to type 'integer' is not valid".
Dim DeliveryTime as DateTime
Dim DeliveryTime as Integer
In my database the DeliveryTime type is set to Time(7) so i would assume there should be 'Time' which i could use to declare it, but there isnt. What is the correct type i should be using?
Here is my exact code. There error is Input string was not in correct format:
GraphDate4 = String.Empty
DeliveryProducts = "{ name: 'DeliveryProducts', data: ["
If DataReader4.HasRows Then
[Code].....
im confuseing when should i use new to create an instance and when not for example in some program programmer declare a instance with new some times without new
dim o as process
or
dim o as new process
what is deifernces?
I have a question about ASP.Net, visual basic I have 2 LINQ query's, the first one works, the second one doesnt, produces a
"Unable to cast object of type 'System.Data.Objects.ObjectQuery'1[SelmaV2.Products]' to type 'System.Collections.Generic.List'1[System.String]'.
[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.
In trying to add a bit of usage variety to a generic class I'm working on, I ran into this issue with trying to cast an object into an interface instance where the interface is defined inside the generic class.
[Code]...
1) VB Allows non-type template parameters2) VB supports explicit specialization 3) VB allows the type parameters to be used as the base class for the generic type4) VB allows a generic type parameter itself to to be a generic 5) VB enforces that all codes are valid for all types of parametrs
View 1 RepliesHow to use Generic List Where method based on index if there are mutiple 'similar' values, see example below
View 3 RepliesI'm trying to search a generic list of 'User' business objects which has a property called 'Username': If (From u In colUsers Select u.Username Where Username.Equals(strUsername)).Count > 0 ThenI keep getting:Delegate to an instance method cannot have null 'this'.
View 16 RepliesNamespace MyClassLib
Public Class MainClass
Public Sub New()
[CODE]...
Is it possible to make it so that the user using the Class Library has to declare a new Instance of MainClass() before using Subs/Functions in Class2 or Class3?
I'm getting an error after sending a list to a web service.This is the code that is calling the web service:
Dim sProgramInterest As New List(Of Integer)
crmService.InsertProspectGetId(sProgramInterest.ToList)
But I'm getting this error.
[code].....
And here is the code that produces the error
CODE:
How can i cast this one?
What's the main problem if I don't declare the type of a variable? Like, Dim var1 versus Dim var1 as Integer.
View 6 RepliesWhat happens if I do: Dim x As New Int32? Is a object of int placed on the heap? If it is, maybe your application would be able to access global variables faster if they were reference types.
A global variable as an value type should be somewhere at the bottom of the stack most of the time and it might take more time to get to this then to get a object from the heap. Unless it's the same story with the pointer of this object is also at the bottom of the stack of course.
I try to run this code in visual studio 2008 and receive error msg: Keyword does not name a type and name objClass is not declare
CODE:
Dim
objMyClass As New MyClass = ("Hello World")
Console.WriteLine(objMyClass.ToString)
Public Function manyarrays(ByVal ParamArray ints() As Integer,ByVal strs() As String) End Function But it is error . How can i fix it ?
View 3 RepliesI'm trying to declare a generic using a variable of type System.Type, with VB 2005, and haven't found the right approach. Consider the typical:
Dim m_GenObj As MyGenericObject(of T)
Instead of using "T" I want to use a variable of System.Type, for something like:
Dim m_MyType as Type
Dim m_GenObj as MyGenericObject(of m_MyType)
But of course that doesn't work.
Someone (w69rdy) in Stack Overflow helped me out with a great example to handle DB output, that could potentially be NULL, passed into a function. The problem is I can understand the method as written in C# but I am having a problem understanding how to rewrite the method in VB.NET. The method uses generics and I am lost. Here is the method written in C# ..
public T ParseValue<T>(System.Data.SqlClient.SqlDataReader reader, string column)
{
T result = default(T);
if (!reader.IsDBNull(reader.GetOrdinal(column)))
[code].....
How is this written in VB.NET? How does the method signature change when returning a generic type?
I have the following statement, I want to turn it into a Public Shared Function :
If isEmployee Then
Dim employeeInstance As New Employee
employeeInstance = GetEmployeeInstanceByUserId(userId)
[Code]....
Public Shared Function GetWorkerInstance(Byval isEmployee as Boolean) As ...(not sure what to write here)...
There two possible return Type. I'm not sure what I should declare for the function return type.
I have the following sample code in a VB.NET console application. It compiles and works, but feels like a hack. Is there a way to define EmptyChild so that it inherits from Intermediate(Of T As Class) without using the dummy EmptyClass?
Module Module1
Sub Main()
Dim Child1 = New RealChild()[code].....
The other way to do this would be to move the generic code out of the Base class and then create 2 Intermediate classes like this [code]...
Then RealChild would inherit from the generic Intermediate and EmptyChild would inherit from the non-generic Intermediate. My problem with that solution is that the Base class is in a separate assembly and I need to keep the code that handles the generic type in that assembly. And there is functionality in the Intermediate class that does not belong in the assembly with the Base class.
I'm in the process of creating a function which reflects over the properties in a class and adds them to this data structure I have. Some of the properties are generic types.So say we have DataType(Of T) that has a .Value property of type T:
Dim properties = GetType(MyType).GetFields(Reflection.BindingFlags.Public Or _
Reflection.BindingFlags.Instance)
For Each prop As fieldinfo In properties
Collection.Add(prop.Name,prop.GetValue(poco))
Next
In the collection.Add for primitive types (Integer, String, etc....) I just want to add the type... but in the case of generic I want to add the DataType(Of T).Value. I hope there is some work-around but I don't think there is a way because the type of T can not be determined at compile time right? Ideally DirectCast(prop.getvalue(poco), DataType(Of T)).Value would be possible. This is when you hoped even more dynamics appear than whats in .NET 4.0.