Return Generic Of Unspecified Type?
Jun 12, 2011Is it possible to create a function that returns a generic of unspecified type, like this?[code]...
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C# - Make A Function With Return Type Generic?
Apr 29, 2010Currently 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]....
.net - Can A Generic Version Of A Derived Class Override A Base Method Using The Generic Type
Apr 13, 2012Consider:
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.
.net - Determining A Generic Type At Runtime In Non-Generic Class
Aug 14, 2010I have a Journal that records entries for different types: Journal(Of ParentT)
[Code]....
.net - Creating A Generic List Of A Generic Type
Jun 30, 2011I 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.
Generic Cannot Instantiate Instance Of The Generic Type With New?
Feb 8, 2012I 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]...
Warning: Type Library Exporter Encountered A Generic Type Instance In A Signature
May 5, 2009I'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.
Unable To Cast Object Of Type .objectquery To Type Generic.list
Sep 12, 2011I 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]....
Cast Value Type To Nullable Enumeration Type In Generic Object If All Types Are Unknown At Write-time?
Dec 14, 2011I 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.
Using An Interface Defined In A Generic Type From Within The Defining Type
Feb 14, 2012In 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]...
VB Allows The Type Parameters To Be Used As The Base Class For The Generic Type?
Mar 30, 20101) 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 Replies.net - How To Make Function Return Generic Value
Sep 16, 2011I 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]...
.NET : Generic Function To Return A Control?
Oct 14, 2010I 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.
Unable To Cast Object Of Type 'System.Collections.Generic.List`1[System.Int32]' To Type 'crmWebService.ArrayOfInt'?
May 14, 2012I'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].....
Unable To Cast Object Of Type 'ImagesFlag' To Type 'System.Collections.Generic.IEnumerable`1[ImagesFlag]'
Jan 7, 2012And here is the code that produces the error
CODE:
How can i cast this one?
.net - Get A Base Class Method Return Type To Be The Subclass Type?
Nov 23, 2009I have a copy function that I'd like to override in subclasses to return the type of the subclass. Here are my interfaces:
Public Interface IBase(Of T)
Function Copy() As T
End Interface
[Code]....
Error:Events Cannot Be Declared With A Delegate Type That Has A Return Type?
Apr 22, 2010I have a delegate and its event in C# as below:
public delegate UsernameCredentials UsernameRequiredEventHandler( object sender, string endpoint );
public event UsernameRequiredEventHandler UsernameRequired;
On Converting the above code in VB.Net as follow :
Public Delegate Function UsernameRequiredEventHandler(ByVal sender As Object, ByVal endpoint As String) As UsernameCredentials
Public Event UsernameRequired As UsernameRequiredEventHandler
I am getting error on the above line saying that "Events cannot be declared with a delegate type that has a return type".I understand that this is not supported in VB.Net.
Generic Declaration Using Type?
Jul 31, 2009I'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.
Returning Generic Type In .NET?
Mar 7, 2011Someone (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?
Inherit From A Generic Class Without Specifying A Type?
Apr 29, 2009I 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.
.net - Cast To Generic Type At Runtime?
Sep 9, 2010I'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.
.net - Generic Classes (T) - Specifying From A Range Of Type?
Jul 28, 2010This is the code I'm trying to develop:
Public Structure Statistic(Of t)
Dim maxStat As t
Dim curStat As t
[Code].....
C# - Reference Type Key In A Generic Dictionary In .Net?
Mar 16, 2010I have a mutable class that I'm using as a key to a generic dictionary. Two keys should be equal only if their references are equal. From what I've read, in this case, I don't need to override Equals, GetHashCode , or implement IEqualityComparer.
View 5 RepliesConstrain Generic Type Using Where T Struct?
Mar 24, 2010I am looking into generics in .NET, and was wondering about the where T : struct constraint. I understand that this allows you to restrict the type used to be a value type. My question is, without any type constraint, you can do a limited number of operations on T. Do you gain the ability to use any additional operations when you specify where T : struct, or is the only value in restricting the types you can pass in?
I guess the question I am actually asking is that if I were to write, (in a discussion about how to use generics), "Now that you have constrained the type argument to value types, you can also do _________ on/with objects of that type", Is there anything to put in that blank? I can think of things for the other constraints, but not this one.
Convert Boolean To Generic Type?
Jan 13, 2011In VB.NET 2010, how to return a boolean value as generic type without compile warning?
View 2 RepliesCreating A Generic List Of A Specified Type?
May 26, 2010I want to create a generic list - but I want to specify the type at runtime - is there a way I can do this? using reflection perhaps?Something like this...
Public Shared Sub create(ByVal t As Type)
Dim myList As New Generic.List(Of t)
End Sub
Declare New Instance With Generic Type?
Jan 26, 2009I 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?
Generic Constraints That Allow Type To Be 2 Different Classes?
Mar 21, 2012I have a generic function in VB.Net. I also have two classes called A and B. Is it possible to allow the generic constraints on my function to allow the Type to be either class A or B? Class A and B do not share any base classes except for object.
View 1 RepliesHow To Determine If Value Is Instance Of Generic Type
Mar 27, 2010I 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<?>;
.net - Determine If A Generic Parameter Is A Nullable Type?
Mar 3, 2011I 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?