VS 2005 - How To Compare Object Types
Feb 3, 2011
Here's what I'm looking to do. I have an array of objects that all implement a particular interface. What I want to do is search that array of objects for a particular object type.I have to do this in several places, so I'm trying to create a function where I pass in the object array and the type that I'm searching for, and have that function return the object that matches that type - or nothing if no match is found.I wrote the following, but it isn't working, so I'm missing something:
[code]...
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Jun 23, 2012
I need to compare two dictionary values if the types stored are equal, this is what i have
if gettype(Args(key)) = gettype(argtypes(key)) then
'' do something
end if
[Code]....
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Nov 1, 2009
I have a class with a Property called 'Value' which is of type Object.Value can be of any type, a structure, a class, an array, IList etc.My problem is with the setter and determining whether the value has changed or not.This is simple enough for value types, but reference types and lists present a problem.For a class, would you assume that the Equals method has been implemented correctly, or just assume that the value has changed every time the setter is called?If I did assume it's changed, then perhaps I should assume it for value types as well, so that the behaviour is consistent.
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Oct 12, 2010
I want to compare two objects whose type may be diffrent.
For eg, I expects 'true' for comparing 1000.0(Decimal) with 1000(Double) . Similary, it should return true if I compare 10(string) and 10(double) .
I tried to compare using Object.Equals() , but it did NOT work.It return false if two objects have different data types.
Dim oldVal As Object ' assgin some value
Dim newVal As Object 'assgin some value
If Not Object.Equals(oldVal,newVal) Then
[Code]....
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Jan 30, 2012
I want to see if try cast can convert user entered answer to the type I have specified. Here's what I have: Dim t as type = GetType(myType) Dim ans = console.readline() If TryCast(ans, t) <> Nothing Then ... 'Doesn't work` In the example above the intelisense doesn't even show t. How to make it work?
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May 4, 2012
I am trying to query for records where that column IS NULL:
Dim UnassignedSubSvc =
From c In CurrentContext.SubService
Where c.Product.ProductSubServiceId **is null**
Select c).ToList()
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Mar 29, 2010
I am having some trouble creating an object array of different object types. Here is what I have so far:
Public Sub New()
Dim b1 As New Book("Book Title 1", "Gold Book Publisher", 1.0, "Bob Jones", "192DJDJD212", "01/02/10")
Dim b2 As New Book("Book Title 2", "Gold Book Publisher", 1.0, "Bob Jones", "192DJDJD212", "01/02/10")
Dim b3 As New Book("Book Title 3", "Gold Book Publisher", 1.0, "Bob Jones", "192DJDJD212", "01/02/10")
[code]....
If I define the array As Book (Public publicationArray(6) As Book) or Magazine (Public publicationArray(6) As Magazine) I am able to access the properties of that class but not both. I think I need to define a type for each array instance but not sure how to do this.
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Sep 27, 2010
I understand that different data types have different uses, String for text, Integer for numerical ect. However, if the Object type can be used for ALL types and supportive of everthign then why should i worry about using correct data types such as string and integer if i can just use "Object" for them all and it will work.I could do
Dim Test as Object = "John"
or i could do
Dim Test as String = "John"
They both do the same thing; there must be something very important im missing here but can only think of one thing that it could be; Memory Management.I think that by using a type such as object may take up more memory than using string?
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Jul 29, 2010
I am building an ASP.NET application that needs dynamic tables. That's another issue that I've already posted about (and gotten a pretty good response!). Now, I'm running into another issue - I want to add new rows to my table, but given that I will have 10-12 tables on one page, each containing different objects in their rows (text boxes, check boxes, etc.) I need a way of simply generically adding a new row that has the same objects as the first row in the table. Here's my code:
Private Sub AddTableRow(ByRef originalTable As System.Web.UI.WebControls.Table)
Dim originalRow As System.Web.UI.WebControls.TableRow = originalTable.Rows(1)
Dim insertingRow As New System.Web.UI.WebControls.TableRow[code]......
Stepping through with a debugger, I see that this strategy is working - but the additional table row still doesn't appear...and still does when I do this statically.
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Nov 30, 2011
I have a function that will be passed an object that contains MANY variables. These variables all get stored in a database. Later a new object will be passed to my function and most of the time it will be identical. But sometimes one or two variables will be different and I'll have to take various actions based on those changes. Other than looping through every variable and comparing it to every stored version of that variable, how might I do this? Can I some how generate a hash value for an entire object? Since the object will be the same most if the times it is passed to me this would be a quick way to determine that nothing has changed.
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Apr 15, 2011
I'm trying to figure out how find an object's type when it is a subclass of another object and I only know the string value of the object's type's name.I created the follwing classes:
HTML
Public Class word
End Class
Public Class noun[code]....
The problem is, using 'GetType' to check pn against a string value, I can only see that pn is a properNoun, not that its parent classes are noun and word.Is there a way to check pn against the string value "noun" or "word" and get back a positive result, indicating that pn is indeed a noun and a word as well as a properNoun?
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Feb 10, 2010
My quest is in regards to xml serialization. I need to get rid of the root node of a collection. I don't have access to my source now so I'll just try to generalize
public class SomeClass
'...some other properties...
<XMLArray(isnullable:=true), _
<XMLArrayitem(datatype:=(getType(object1)), _
[code]....
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Nov 9, 2011
I am having problems with my code, where I get the "Object cannot be cast from DBNull to other types" message when Insert(). I get the message on every Insert to this table, even though the data is successfully inserted. If I Update the same data after Insert(), it does so without error. I have checked my values and none of them are DBNull. Even when the same values are passed on Insert that are passed on Update.
My code is :
Private Sub Save()
Dim bo As tbl_GL
bo = New tbl_GL()
bo.ConnectionString = AppConfig.ConnectString
[Code] .....
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Feb 15, 2011
Given a list of objects, I'd like to print a string version of them just in case the object.ToString() result is a relevant string.By that I mean I don't want to get things like:
obj.ToString() -> System.Collections.Generic.List`1[MyLib.Dude]
obj.ToString() -> System.Collections.Generic.Dictionary`2[System.Int32,System.DateTime]
obj.ToString() -> System.Byte[]
But I want to get things like:
obj.ToString() -> Hi
obj.ToString() -> 129847.123
obj.ToString() -> Id = 123
What should be the best way to implement this in a method:
Public Sub PrintInterestingStuffOnly(ByVal coolList as Ilist(Of Object))
For Each obj in coolList
'insert solution here
[code].....
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Jul 1, 2010
I am self learning vb. Currently i am developing an accounting application(Just finished one form). This is the first time i have come across 'Option Compare'.I have few text comparisons in my first form, Currently i am comparing both the text's by converting it to lower. Should i change the option compare to Text and remove the ToLower conversions. Will it make difference in the performs and is setting the Option Compare to Text proper for this kind of applications.
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Jan 22, 2009
Im trying to compare two lists,to find out how which items occur in both lists. I also want to test for duplication within a list.Now, the obvious way is a loop/compare which works fine for a low number of items. Beyond 10000 items, things slow down much more than a factor of 10.
Dim List1 As New List(Of String)
Dim List2 As New List(Of String)
Dim List3 As New List(Of String)
[code]....
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Jan 1, 2008
I have set my datasource on my datagridview to be a subset of rows as follows:
dg.DataSource = myDataSet.testTable.Select("id=" & id)
But I get a runtime error that Operator '=' is not defined for types 'Object' and '1-dimensional array of DataRow' There should be an easy way to do this that doesn't involve creating new tables, etc.
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Sep 28, 2009
1)What are different types of Cursors?
2)What are diff types of locks? In some sites-
Four types of locks availbale in ADODB
1.Optimistic
2.pessimistic
3.batch optimistic
4.readonly
In some sites Forwardonly , lock,adLockUnspecified
What are exact locks,can somebody tell me?
3) What is Z order Precedence?
4) dim X,Y as integer
They ask me X is of which datatype in VB & in VB.net? I told integer in both Vb & VB.Net,they told me wrong?
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Jun 8, 2012
Lets say I click a button on a form that calls a function in a data access class. This function inserts a record into a table in a database. The function returns an integer value for the record id of the newly inserted record. Now lets say the insert failed (syntax error, timeout, whatever). I can return a zero to the calling routine to indicate the failure, but not the error message. So in general, what's the most appropriate way to handle getting information back to a calling routine when the return parameter data type doesn't allow it?
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Sep 29, 2009
I made a little application that check the servers and if the servers go off for more than 5 mins then the program will sent me a mail.My problem is how do I compare the server date time witch display in a textbox to the real datetime which display in a label also how do I run the program constantly till the user decides to exit by clicking on a exit button.
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Aug 16, 2009
i want to compare a column present in the access database BankAccount table with a field present in the form named as account......
[Code]...
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Sep 4, 2010
i have this code in asp.net 2005 page under vb codes on myreader.Read gives me "variable myreader is used before it has been assigned a value a null reference exception" and in the ex msg " object reference not set to an instance of an object".
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Nov 3, 2009
i trying to do login form, if user & password correct, then will show Main Form. First time login is no problem at all, after closed the Main Form, it will back to login form. Problem come when i try to relogin again & show "Object Reference not set to an instance of an object" when try to access the database. Attach my code here:
frmLogin -
AppPath = Environment.CurrentDirectory
DBFilename = AppPath & "DatabaseBT2 Test Results.btd"
frmMain.txtDBFilename.Text = DBFilename
[Code]....
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May 12, 2009
For some reason, on the line where I try to set the value of the key, I get the following error:
Object reference not set to an instance of an object
vb Private Sub writeToKey(ByVal regValue As String)
Dim regkey As RegistryKey = Registry.CurrentUser.OpenSubKey("SoftwareMicrosoftWindows NTCurrentVersionWindowsDevice")
regkey.SetValue("Device", regValue, RegistryValueKind.String) 'error occurs here
regkey.Close()
End Sub
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Jul 4, 2011
I have a listbox of a object called Account, which has 2 fields, password, and username. How can I compare a New Account to all the accounts in the list and see if the password matches?
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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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May 1, 2009
how can I troubleshoot "Object cannot be cast from DBNull to other types."?I am using a combobox, to retrieve the price and discount price of the service, If I select an item in combobox3 once, error will not occur, but if I select a item again in combobox3, "Object cannot be cast from DBNull to other types." will occur..here is my code
Private Sub ComboBox3_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox3.SelectedIndexChanged
Dim ds As New DataSet
[code]....
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Jun 20, 2012
how can I troubleshoot "Object cannot be cast from DBNull to other types."?I am using a combobox, to retrieve the price and discount price of the service, If I select an item in combobox3 once, error will not occur, but if I select a item again in combobox3, "Object cannot be cast from DBNull to other types." will occur..
here is my code
Private Sub ComboBox3_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox3.SelectedIndexChanged
[code].....
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Mar 14, 2010
I am attempting to figure out why this code is not working in VB2005.I am trying to run a check on a set of 25 buttons in a 5 by 5 square. they are label "cmd" & X & "x" & Y whereas X and Y are the x,y coordinates.cmd1x1 through cmd5x5 I am trying for this code to set varMapBefore() to either 0(for D) or 1 (for L) for each of the buttons cmd1x1 through cmd5x5 and then join them together at the end for an output.but varMap wont act like an object. What am I doing wrong?
Private Sub cmdStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStart.Click
Dim varMap(0 To 24) As Object, varMapBefore(0 To 24) As String, varMapAfter(0 To 24) As String, varCheck As String
Dim varCount As Integer, varX As Integer, varY As Integer
varCount = 0
[code]....
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Mar 3, 2010
I have two textbox in my application.
Textbox1.Text="19-Jan-2010"
Textbox2.Text="Jan 2010"
May I know how can I compare that Textbox1 and Textbox2 text is within same month and same year?
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