Copy An Object Of An Unknown Type?
Jul 29, 2010
Rather than giving the very specific case (which I did earlier), let me give a general example. Let's say that I have a function, called callingFunction. It has one parameter, called parameter. Parameter is of an unknown type. Let us then say that I wish to copy this parameter, and return it as a new object. For example, in pseudo code, something along the lines of...
[Code]...
EDIT: Additional Information The first time I posted this question, I received only one response - I felt that perhaps I made the question too specific. I guess I will explain more, I have an ASP page with 10 tables on it. I am trying, using the VB code behind, to come up with a single solution to add new rows to any table. When the user clicks a button, a generic "add row" function should be called.
The difficulty lies in the fact that I have no guarantee of the contents of any table. A new row will have the same contents as the row above it, but given that there are 10 tables, 1 row could contain any number of objects - text boxes, check boxes, etc. So I want to create a generic object, make it of the same type as the row above it, then add it to a new cell, then to a new row, then to the table.
[Code]...
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Dec 14, 2011
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.
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Dec 19, 2011
I am trying to create a Sub that can take an object and add a load of event handlers for it, but the object can be any one of N types that all have these events. How can I do this? If I just have it as an Object as below AddHandler complains that the event does not exist for Object.
[Code]...
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Feb 15, 2010
Writing 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)
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Mar 31, 2011
same errors or something related to System.windows.forms. Unable to cast object of type 'Public_Information_System_Remake.PIS' to type 'System.Windows.Forms.TextBox'.
[Code]...
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Jul 16, 2010
The addhandler function works this way: AddHandler Button1.Clicked, AddressOf Button1_Clicked, However, I have an unknown object: Dim o as Object, But I can't add handler for this object AddHandler o.SomeEvent, AddressOf SomeFunction, How do I add handler for unknown objects as stated above?
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Jun 6, 2012
I have problem in my application when updating 3 items otherwise it is as good as work. The problem is when updating the username to the access database an error showing that "Datatype mismatch" when updating the date and time field an error occurs and tells that the "Unknown field type". This is my code where bold faced lines have errors:
Dim objCmd As OleDb.OleDbCommand = New OleDb.OleDbCommand()
objCmd.Connection = con.con
'Make a command to insert data
[Code].....
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Sep 14, 2009
I have recently moved from VB 2003 to VB 2005. While I am finding a lot of the new features quite useful, I am having trouble with List (of T). I want to be able to do something like this
Function GetList(MyObjectType as Type) as datatable
Dim list as new List(of MyObjectType)
End Function
Function GetList(MyObjectType as String) as datatable
Dim list as new List(of GetType(MyObjectType))
End Function
VB 2005 does not allow me to do this at all. Must the "type of" be srongly declared at all times? Can't this be done dynamically?
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Jan 9, 2010
I want to create a new object of a class which is not predetermined before run-time. Something along the lines of:
[Code]...
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May 9, 2012
I have the code below giving me grief because it gives unknown error (0x80005000) when trying to add a user to a second group[code]...
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Jun 8, 2012
I'm having some trouble with a program i'm making, everytime i try to run the form that runs this code:
[Code]....
Beep.tone(1000, note, 240)<< this is the line that throws the exception. i have exactly the same code on my main form and it runs perfectly everywhere else, only in the form where it is supposed to be run do i get an exception. Note array is public and i can access it fine from everywhere else, and the custom class beep works fine.
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May 18, 2011
I'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)()
[Code]....
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May 13, 2011
I have an array of unknown (to the current method) class objects. I do know that each class has a property called "Number". I am trying to write a LINQ query where I am looking for the object with the next Number in sequence. AKA, I'm at Number 8, use a LINQ query to find the object where Number=9.
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Jul 25, 2009
I have a sub that handles when 14 ComboBoxes have their Index changed. I am able to cast the sender of the event, and obtain properties from there. However, after that, I want to be able to change the properties of the actual sender, rather than the cast one.[code]...
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Sep 21, 2011
I have a code below to make collection that bind to a gridview able to sort by clicking on the column header. The problem here is "IPerson" is unknown at compile time. I want the delegate type able to decide by getting from gridview datasource.[code]....
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Aug 16, 2011
I have written a function to generate a random string with specified length. In that I have used 'Random' function. when I have executed it, it is throwing an unhandled exception.Please suggest me some solution. Below is the code I have used:
[code]...
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May 10, 2011
I have recently updated a legacy compact framework application to support Windows Mobile 6.5 but after going through my backwards compatability testing I have an issue with the WinCE 5 device.When attempting to run the application from both the EXE and the debugger I get the "An unhandled exception of type 'System.TypeLoadException' occurred in Unknown Module." exception but its not giving me any idea which dll / type it has issue with.The changes do work on the Windows Mobile 6.5 Motorola device and the Pocket PC 2003 Psion Device but not on the WinCE5 Psion device.Does anyone have any ideas how I can find out which reference is causing me the issue. I have tried removing the new references to the Symbol barcoding and imaging libraries but I am still getting the same error.OK, it looks like the .Net Compact Framework installation had corrupted some how. I flattened the device, reinstalled and everything appears to be working.
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Sep 23, 2010
I'm trying to check if a LINQ Entity exists in its table, but at design time I dont know what type that entity is. So I figure I'll just get the table, and try the Contains method on it. But I cant get the table in such a way that I can query it at design time.I've tried the GetTable method on the datacontext, but I dont know how to cast it to the appropriate type when using GetTable(Of). GetTable(Type) works, I just use Entity.GetType(), but then I don't know how to query the ITable thats returned.To try and cast the ITable to something useable, I created an interface(IWhatever) that could implement properties that are native to all of my entities I would encounter. [code]
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Aug 19, 2010
program supost to control (projector - done..., webcam - idk how do i read FPS of the camera ..., arduino - will take me 5 min...)
here is the code of form1:
[code]...
it chrashes here is the error : An unhandled exception of type 'System.StackOverflowException' occurred in Unknown Module.
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Sep 8, 2009
System.ExecutionEngineException was unhandled Message: An unhandled exception of type 'System.ExecutionEngineException' occurred in Unknown Module.There are no further details and the stack trace window is blank I was just wondering how it would be best to work out where this error message is happening - i really don't want to put a million debug.prints in there to work out what functions were last called etc.
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Oct 22, 2009
Using Access 2003 and VB code, I have created a form with a number of labels. The labels will display an employee's names. I have named the labels name1, name2, name3...etc. Using an ADO data set and DCount I have determined the number of names in an Access table (the number of names can vary). What I want to do is for each record in succession to pick the first name and surname from the data set , combine them into a full name (this part has been successful), and then set the full name into the label caption in succession. Example: full name 1 into name1, full name 2 into name2, full name 3 into name3... until all names appear as labels on the form.
I created a counter to and a variable to increment the label number but when I address the caption property of the variable containing the new label (e.g. name1, name2..etc.) it throws an errer at runtime. Here is the code:
[Code]....
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May 7, 2009
This 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.
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Jan 25, 2011
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.
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Feb 1, 2012
In VB.net, when I retrieve a value from a list do I get a copy of that value or a reference to it?
dim blah as someObject
dim listOfBlahs as list(of someObject)
listOfBlah.add(new someObject(1))
[Code]....
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Jul 5, 2010
I've got a piece of code in a project (MyProject) that contains early bound object from a referenced assembly (We'll call it CommonAssembly):
Dim myObject As CommonAssembly.MyEarlyBoundType
now I have another assembly that is dynamically loaded because it is not present in all projects:
Dim myLateBoundObject As Object = AppDomain.CurrentDomain.CreateInstanceAndUnwrap("Utils", "Utils.MyLateBoundType")
MyLateBoundType derives from CommonAssembly.MyEarlyBoundType, and I want to cast myObject to myLateBoundObject and then programmatically invoke the additional
[Code].....
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Apr 5, 2009
i always get this error when i tried to update my table: Unable to cast object of type 'System.Object[]' to type 'System.String[]'.
i only want to update STATUS, ENDTIME, and PRICE
the data type of each field are:
STATUS = nvarchar
ENDTIME = smalldatetime
PRICE = money
[Code]....
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Feb 15, 2011
I 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
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Jan 28, 2012
when 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].....
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Apr 19, 2010
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"
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Apr 13, 2011
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'"?
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