In VB.NET, if I create a class it is a reference-type. But, if that class it chock full of value type properties, how is this handled? If the class is instantied but never filled, I suspect a pointed for to the heap is allocated. But is more space allocated on the stack for all of it's value type properties?
View 4 RepliesHow can I get all the properties of a class that implement a specific base class or interface? I have a properties class that contains several other property classes. Some, not all, of these classes implement an interface. I would like to know if it's possible to iterate over all properties of parent class for child-classes that implement the target interface. It sounds like a job for reflection? I'm just not sure how. Can it be done via the "PropertyInfo" object?
View 1 RepliesI've come from a Assembler and C/C++ background, so I understand the concept behind reference types versus value types in vb.net. Also, I've read Jon Skeet's article regarding references and value types and I understand all of that. My question is: How can you tell if a given type is a reference type or a value type? Is it simply that all integral types (ints, floats, etc.) are value types and all classes are reference types? (If so, where do strings fall?)
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I wanted to define a property which accepts decimal numbers and do some process on the value and return string such as the below:
Public Property Amount() As String
Get
Return Utility.PaddingRight(Me.msAmount.ToString(), 10)
End Get
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But compilers warns "Set parameters must have the same type of the containing property."It doesn't look like it should throws an error since it looks legit.
In .NET, integer data type is a value type(stack) and String is a reference type(heap). So If a class A has an integer, and a string type object in it, and a class B creates an object of class A, then how will this object of class A be stored in memory? In stack, or in a heap? This was asked in my Microsoft interview. Need to understand how I fared.
View 3 RepliesUnable to cast COM object of type 'System.__ComObject' to class type 'rjsDocMan.Folder'.Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface.The code where it is flagging the error is:
<div style="color: Black; background-color: White;">
treeview += AddChildren(Session("DocMan").RootFolder)
</div>
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I 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
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i was trying to inherit System.Type. this is what i have:
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and anyway the real problem is that inheriting System.Type without declaring my derived class as 'MustInherit
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 RepliesI also.But problem is I generally mug up things for identifying that it is value type or reference type Like class is reference type and structure is value type .. I made a list and paste in my mind .. But of course it is wrong. how to differenciate between value type and reference type by its behaviour or looking at its properties or run time behaviour etc .So that I need not to remember the list..
View 4 RepliesI have the following two tables defined...
CREATE TABLE [LogLevel] (
[Id] int primary key
,[Name] nvarchar(50) not null
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After creating a fresh endity model, I add the two tables above. When I try to build I get the following errors...
Type argument 'Inxsol.CommandPlan.Data.Model.Log.LogLevel' does not satisfy the 'Class' constraint for type parameter 'TEntity'.
Value of type 'System.Data.Objects.DataClasses.EntityReference(Of Inxsol.CommandPlan.Data.Model.LogLevel)' cannot be converted to 'System.Data.Objects.DataClasses.EntityReference(Of Inxsol.CommandPlan.Data.Model.Log.LogLevel)'.
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Code: Dim dom As New DOMDocument30 dom.async = False
dom.Load(serverAddress & "/App/filelist.jsp?type=content")
For i = 0 To dom.childNodes.item(1).childNodes.length - 1 downloadfile(dom.childNodes.item(i), mcount, currentpath) Next
The above code is activated upon clicking of a button. i have the server address declared. and using the domdoc to load the jsp file to generate the xml data. and using for loop, i call the download file function which accepts the following parameters
Code:Public Sub downloadfile(ByVal domdoc As Xml.XmlNode, ByVal totalcount As Integer, ByVal currentpath As String)
The totalcount and currentpath work fine, but when i pass in the dom.childNodes.item(i) , error pops up.
--------------------error message------------------------------------------Unable to cast COM object of type 'System.__ComObject' to class type 'System.Xml.XmlNode'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface.-------------------------------------------------------------------------------
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I have a class in which some of the fields are also classes.I can put values in the "normal" properties, but in the others when o try to assign values it gives the: "Object reference not set to an instance of an object"But the code compiles fine.
dados_Defenicao = New ServiceReference1.draftClaimEntryDefinition
dados_Defenicao.arCode = "123"
dados_Defenicao.claimMarket.warrantyType = "w" - Here it gives the error
How can i fix this ?
I have a class in which some of the fields are also classes.
I can put values in the "normal" properties, but in the others when o try to assign values it gives the: "Object reference not set to an instance of an object"
But the code compiles fine.
dados_Defenicao = New ServiceReference1.draftClaimEntryDefinition
dados_Defenicao.arCode = "123"
dados_Defenicao.claimMarket.warrantyType = "w" - Here it gives the error
When I try this, I get the compiler error below:Return TryCast(obj, Double?)'TryCast' operand must be reference type, but 'Double?' is a value type.
This confuses me, I thought that when you make a value type nullable, boxing will be applied - which results in a reference type?
I am trying to figure out how to get at an anonymous typed object's properties, when that anonymous type isn't created in the current function.
Specifically, I am binding an ASP.NET ListView to LINQ resultset, then trying to process each item in the ItemDataBound event.
Option Explicit On
Option Strict On
Class MyPageClass
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If I have a complex structure which contains properties which are both simple and complex types, how can I iterate over all the properties of this structure and any child properties which are not simple types?
I have a complex type called file, which contains lots of string properties and some which are other complex types which contain similar structures, eventually the whole structure breaks down into strings.
At the moment my code looks like this:
Dim file As New File
Dim props() As PropertyInfo = file.GetType.GetProperties()
_propList = New CheckBoxList
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This works, but it is ugly and I am not at all happy with certain chunks, specifically the type comparisons to establish if this is a date, string, decimal or boolean which are the potential low level types which I want to get out.
In C# it would seem these type comparisons are easier, but i seem to have to create an instance of a given type to be able to use GetType to return its type.
I'm doing some reading up on the differences between Value types and Reference types - is there any quick/easy way of telling whether a type is Value or Reference? I couldnt see anything in Intellisense so had a look at MSDN pages for a few classes [URL]but it doesnt seem to mention it there either.
View 11 RepliesI've got a class, lets call it Person, which needs to keep some data (in the form of another class which we will call PersonData) in one of its properties - the problem is that I will have several instances of this person class and they all need their own 'copy' of the data (just in memory, its not a file or anything).Hhow would I do this? At the moment because everything involved is a Reference type, I'm assuming that if I were to create 2 instances of my Person classes and assign the same instance of the PersonData class to their properties then when one Person class made a change to the PersonData it would be reflected in the other Person class right? How can I avoid that and make it so that they both have their own version of the data, without having to repeat the procedure that fetches the data in the first place?
I'll explain my exact situation just in case it helps, but this is more of a general question as I could probably get around it in this case by copying the byte array I receive from the server (hopefully that will make sense once you read the explanation below) :
In this case the data I am talking about copying is actually received from a server via TcpClient. The thing is, when the client requests the data from the server over the network, the server has to go off and query several other servers etc so I do not want to be requesting data from the server every single time as that would be a big waste of resources and time. So when a request is made and data is received back from the server, several of these Person class instances will be created (in reality, its a few different classes but that doesnt make a difference for this example) and each need to have access to the full data that the server has sent back but in some cases the Person instances might need to modify the data and this is where the problem appears as they will all be working on the same data.
i need to do something as the old scholl on vb6, create a control array, i need to put 50 listviews controls and when the form is initialized start asigning properties since i will drag items to each one of those grids, im goin to make a dragdrop event to handle all the 50 controls, dont like the idea of adding handles c1, c2,cn, c50 but whatever, is there soemthing easy to create a routine to change properties and add columns to each one control dinamically?
sample
for x=0 to 50
control(x).property = true or ""
next
I suspect I am being very silly here but I have the following setup
Class MustInherit myBaseClass
'some stuff
End Class
Class myInheritedClassA
[code]....
Running this results in the following error
Unhandled Exception: System.InvalidOperationException:
There was an error generating the XML document. --->
System.InvalidOperationException:
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is there any way of 'Widening' the inherited class to the base class so this would work?
EDIT:regarding XmlInclude(typeof inheritedClass), currently this method could potentially return a number of types of inherited class (i.e myInheritedClassA and myInheritedClassB) is it case of simply having to add each of the inheritedTypes in this tag?
I 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 RepliesAs the reference values are stored in the heap as a data; where do the type information of any reference value is stored?If there are a couple of instances of class Artist; when they are stored in the heap how the .Net tags those memory blocks as type of Artist?
View 3 RepliesHow to get Hardware properties in VB Express 2010 like video card name and memory type?
View 2 RepliesDim a as Type=GetType(className) would gimme the type. But I have only the name of the class as string. I want something like GetType("class1") which would return the type.
View 2 RepliesI have a class that hosts inside other classes that can host otherclases as well and so on.
I want to change the value of one property (PropertyA) in all classes down the tree.
How can i do that when i dont know the the type of class inside?
How can i iterate through the classes hostes as proeprty of the mother class?
I am trying to use reflection but i get just the properties of the first class
I m working on one of vb6 projects. There are total 3 projects. One of them is ActiveX Exe is and has main method, second one is also AxtiveX Exe but doesnt have main method (only Classes) and third project is of ActiveX Dll.Well I m trying debug and issue and trying to put all 3 prjts in 1 Group prject but some how I cant add reference of 2nd prject into the first one. I get an error of " cannot be referenced because its project type is exe" but I can add a ref of its compiled exe but this doesnt help in debugging of whole prjt.
View 7 RepliesI'm learning LINQ and VB and just spent an hour trying to access the fields of an anonymous type defined in a linq query. The key (I learned) is to convert the query to a list before you try to iterate through it with a for loop. How to access property of anonymous type in C#?
This does not work: edit (this compiles, but intellisense does not recognize the type)[code]...
Each time I create a program, if I don't change the CPU type to x86 in the Project Properties, Compile, Advanced Compile options, it doesn't work. For example, if I hit the drop down button on a combo box, there will be no data, but after switching to x86, there is data. How does changing the CPU type affect how others (such as when its being graded) view the program? If the program is not run on an x86 system, would it appear to not work then?
View 1 RepliesI'm trying to create a generic function to build a Linq expression from a list of Telerik grid filters. I'm trying to stay clear of dynamic Linq. Because I don't know the type that I'm building the expression for, I'm attempting to use reflection in the lambda functions to refer to a property, but after applying the fix suggested by @JaredPar I get the error, "The LINQ expression node type 'Invoke' is not supported in LINQ to Entities." Is there any way around this? here is my code:
Public Shared Function buildRadFilter(Of T)(ByVal filterExpression As List(Of GridFilterExpression)) As Expressions.Expression(Of Func(Of T, Boolean))
Dim returnPred = PredicateBuilder.True(Of T)()
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