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 Replies
As 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 RepliesI have a storedproc accepts parameters in XMLtype as
CREATE OR REPLACE PROCEDURE GetDetails(
p_para IN XMLTYPE,
[code].....
I'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?)
[Code]...
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 Replieswhen view in browser, i got this error: Unable to cast object of type 'ASP.webform1_aspx' to type 'System.Web.UI.WebControls.Button'.
how should i solve this problem?
Line 7: If Not Page.IsPostBack Then
Line 8: Dim rowIndex As Integer = 0
<b>Line 9: Dim btn As Button = DirectCast(sender, Button)</b>
[Code].....
I had write code (just for learning), the codes :
dim Temp as string
Temp = Recordset("
Table_Field")
but, when I start Debugging the error messages "Unable to cast object of type 'ADODB.InternalField' to type 'System.String"
I am implementing IMAPI2 into my vb.net project but ran into a wall. I am getting the message Unable to cast object of type 'IMAPI2FS.FsiStreamClass' to type 'IMAPI2.IStream' when trying to start the burn. I googled around and found this is something that microsoft hasn't fixed.. which basically renders IMAPI2 useless in vb.net.
I found a post on codeproject.com by eric hadden who combined the IMAPI2.dll and IMAPI2fs.dll into an c# interop file. I also see the IBURN interop in microsoft SDK samples. I'd like to use either, but it's in c# and I'm using vb express. Does anyone know a way to get the interop into visual basic or a way around "Unable to cast object of type 'IMAPI2FS.FsiStreamClass' to type 'IMAPI2.IStream'"?
I'm having a problem with converting from one source type to a destination type. I have a form with 2 buttons (button 2 uses the OpenFileDialog to have the user open an excel file set to NewFile),(button 1 takes the contents from specific cells in NewFile and arranges them how I need into oXLApp1).
The error I get is "Unable to cast object of type 'System.IO.FileStream' to type 'Excel.Application'." in line 14 of the code below.
Public Class Form1
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
[Code]....
I'm new to VB 2005, the code below is actualy coded from VB 6 and just converted it to VB 2005. I'm having trouble with line that's on bold letters.In VB 6 this works just ok. By the way the error message is "Unable to cast object of type 'System.String' to type 'ADODB.Connection'." [code]
View 5 RepliesI can't cast my objects. I get: "Unable to cast object of type 'ClassA' to type 'ClassB'".
The service Class:
Public Class svc_Insp
Implements Isvc_Insp
Public Function Test(ByVal pm_income As ClassC) As String Implements Isvc_Insp.Test
[code]....
Unable 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>
[code].....
I saw this thread and I had simple answer in mind. To use custom enumerator class. So I was trying to make one for that guy, which would have one more property to check whether its has reached end or not. It would also provide current position.I'm getting an error "Unable to cast object of type 'SZArrayEnumerator' to type 'WindowsApplication1.myEnumerator'." at the line 6 [see below].However, return type of values.getEnumerator says its IEnumerator. [code]
View 14 RepliesI 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]....
Columns 0 & 1 are filled from a DataAdapter from Access Database and three are added. I had this working, but I changed it to check for the column "Feed" so I could add several Locations. At first this worked,but I did someething in perfecting it and it now fails after filling the first row of the datagridview (dgvFdMed).I ran a check and the table LotsTab has 8 rows filled. Column 1 & 2 are strings and the database appears they are fine. The added columns have just been created with no value. My plan is to enter the values and then use the data from the grid.
Private Sub sfillGrid(ByVal Loc As String)
Dim i As Integer
Dim column As DataGridViewColumn
[code]....
I have 2 Child forms inside a parent. For example, FrmChild1 contains a "Friend Sub" I wish to call.I would like one of the child forms to call that sub from another child form (we will call it FrmChild2. The following code works, but when it's done going through the "For Each", I get a "Invalid Cast"
' THIS CODE IS IN FrmChild1
For Each mFrmChild2 As FrmChild2 In FrmParent.MdiChildren
mFrmChild2.GuestRefresh(False)
Next
Error after calls are made:"Unable to cast object of type FrmChild1 to type FrmChild2.
I am getting this error No mapping exists from object type System.String[] to a known managed provider native type.The code is
Dim conn1 As SqlConnection
conn1 = New SqlConnection("Data Source=win2008-2;Initial Catalog=h1tm11;User ID=sa;Password=#1cub3123*;Persist Security Info=True;")
' Dim conn1 As String = ConfigurationManager _ .ConnectionStrings("Connectionstring").ConnectionString()
'conn1.ConnectionString = ConfigurationManager.ConnectionStrings("Data Source=win2008-2;Initial Catalog=h1tm11;User ID=sa;
[code].....
the error occurs at adapter.Fill(table)
Dim addressstring1 As String = txtpostcode.Value.Trim()
Dim addressstring() As String = Split("addressstring1", ",", 1)
I have a series of API calls that are returning J# data types. I have been able to convert most of the data types (Integer, Boolean, Double, Float, etc) just fine.What I need to do now is convert a java.Util.Collection to a VB .NET collection (ArrayList)
Here is my attempt:
Public Function MakeDotNETCollection(ByVal javaCol As java.util.Collection) As Collection
Dim dotNetCol As Collection
[code]....
I keep getting a runtime error "Unable to cast object of type 'AbstractListlistIterator' to type 'System.Collections.IEnumerator.
I am building a software which will be used to create a remote desktop connection. However I'm getting this error:
Unable to cast COM object of type 'System.__ComObject' to interface type 'MSTSCLib.IMsTscNonScriptable'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{C1E6743A-41C1-4A74-832A-0DD06C1C7A0E}' failed
due to the following error: Δεν υποστηρίζεται τέτοια διασύνδεση (Exception from HRESULT: 0x80004002 E_NOINTERFACE)).
[Code]...
I am using a background worker and am attempting to use the following code. However I keep getting this error on i "Unable to cast object of type 'ObjectCollection' to type 'System.Array'."
Private Sub btnVerify_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnVerify.Click
myArray = listProxies.Items()
BackgroundWorker1.RunWorkerAsync()
End Sub
[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.
I have given reference to Microsoft HTML in COM (am using VB 2008)
"Unable to cast object of type 'System.Windows.Forms.HtmlElement' to type 'mshtml.IHTMLElement'."
I want to retrieve all the properties like the class name, html id of every object in the web browser. I am getting the above exception when i try to direct cast it.[code]...
I am attempting to launch a specific form depending on the selected node of a treeview on the doubleclick event. The code I need to use to launch the form is a little bulky becuase I have to ensure that the form is not disposed, and that the form is not already openbefore launching a new instance. I'd like to have all of this checking happen in one place at the end of the function, which means that I have to be able to pass the right form type to the code at the end. I'm trying to do this with a System.Type, but that doesn't seem to be working
View 1 RepliesWriting an asp.net mvc app and i have something like this...
Public Class AA
'... has some variables...
End Class
Public Class BB
[code]....
So, now in my program, i just want to copy object of type AA to an empty variable of type BB?it makes sense to do this, as i expect all the fields in AA type object to be copied to the newly created BB type object, and the ExtraVariable in the BB type object i would (will) just assign a value to it later (after the copy) on my own time!!I know copying BB type to AA type would not be appropriate as there would be lost data!But im trying to copy AA to BB, I've used both DirectCast and CType to do this, and i keep getting "unable to cast" error!
Note: I'm using vb.net (but can read c#, no problems)
I have been trying to use vb2008 to automatically update CustomDocumentProperties fields that I have set up within a pro-forma document. I can load the Word application and word document without problems.I want to update the CustomDocumentProperties fields with data read from a dB. To do this I am assuming that I need to iterate through the CustomDocumentProperties fields within the word document and when one is "found" that matches the data I wish to merge then assign the dB value to the field.The problem is that I am getting an exception error when I try to reference the document customdocumentproperties
"Error : Unable to cast the COM object of type 'System._ComObject' to interface type 'Microsoft.Office.Interop.Word.CustomProperties'. ...... "
my code looks like;
Dim WordApp As Word._Application
Dim odoc As Word._Document
Dim BContinue As Boolean = True
[code].....
For I = 0 To 10
If Items.Count = 0 Then Exit For
Dim T As New Thread(AddressOf Thread)
T.Start(New Object() {"Test", "Test"})
[code]....
When I put same code in empty project it works.
I 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 RepliesThis error makes no sense to me[code]...
Unable to cast object of type 'DynamicTreeNode' to type 'DynamicTreeNode'.
I have an inherited TreeView with an inherited class called DynamicTreeNode inside it. I am trying to loop through the DynamicTreeNodes in the TreeView.Nodes property which is causing this error.
I have a requirement where I need to have a "type safe" way of accessing property names, without actually instantiating an object to get to the property. To give an example, consider a method that takes as arguments a list of IMyObject and a string that represents a property name (a property that exists in IMyObject).
The methods implementation will take the list and access all the objects in the list using the property name passed... for some reason or another, we won't dwell on that!!
Now, I know that you can do this using an instantiated object, something like ...
Dim x as MyObject = nothing
Dim prop As PropertyInfo = PropHelper.GetProperty(Of MyObject)(Function() x.MyProperty)
Where my helper method uses reflection to get the name of the property as a string - there are numerous examples of this flying around on the web!
But I don't want to have to create this pointless object, I just want to do something like MyObject.MyProperty! Reflection allows you to iterate through a types properties and methods without declaring an object of that type... but I want to access a specific property and retrieve the string version of its name without iteration and without declaring an object of that type!
The main point here is that although I am trying to get the property name as a string... this is done at run time... at compile time, I want this to be type safe so if someone changes the property name, the compilation will break.
how can I convert an object type to a GUID type in VB.NET?
View 3 Replies
