Checking Objects Type By String
Apr 15, 2011
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 following classes:
HTML
Public Class word
End Class
Public Class noun
Inherits word
[Code] .....
Then, in my code I create a new properNoun and check to see if it is a properNoun, noun or word:
HTML
Private Sub checkTypes()
Dim pn As New properNoun
MsgBox("Is a properNoun: :" & TypeOf pn Is properNoun) 'TRUE
MsgBox("Is a noun: :" & TypeOf pn Is noun) 'TRUE
[Code] .....
I correctly see that pn is a properNoun, a noun and a word. 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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Jan 18, 2012
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Using conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmdRecord As SqlCommand
[code]....
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Jul 7, 2011
I have a function that is getting passed a String and a DataRow.The String is a custom formatter. The idea is to do this
String.Format(passed_in_String, DataRow("ColumnINeed"))
The reason this is being done is at this point we have no idea what the column contains.However, if the formatter is "{0:MM/dd/yyyy}" and the DataRow("ColumnINeed") is an integer containing 42, String.Format is returning: MM/dd/yyyy In this situation I need it to throw an exception instead of returning nonsense.Is there anyway to make String.Format throw an exception if the object does not match what the format string is expecting?
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Jun 23, 2012
I am getting this error, Not sure why it is happening "Error The SqlParameterCollection only accepts non-null SqlParameter type objects, not Int32 objects."I have tried with all sorts of possibilties, now try to enter default data as dummy data,
Using connection As New SqlConnection
connection.ConnectionString = ConfigurationManager.ConnectionStrings("DentalDeviceConnectionString").ConnectionString
connection.Open()[code].....
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Feb 4, 2011
Im using Outlook Automation to parse through a PST file, and Im having trouble checking attachment types. Im attempting to check the attachment to see if it is a MailItem, but its not working, heres the syntax that I'm using.
Dim msgAttch As Outlook.Attachment
If msgAttch.Class = Outlook.OlObjectClass.olMail Then
'Check MailItem
End If
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Apr 14, 2009
gv1 is a grid !!
gv1.DataSource = minfo.Invoke(Activator.CreateInstance(classtype), inputParameterStore)gv1.DataBind()
What i get from minfo.invoke i am binding to the grid gv1 !!! But unfortunately its not working for all minfo !!!! Few errors are like :
return type is not IListSource ,IEnumerable or IDataSource !!!!
Hence i need to check if :
minfo.Invoke(Activator.CreateInstance(classtype), inputParameterStore)
returns IEnumerable or IData Source or IListSource !how to do that ?Also if return type is none of these i should display the result in a Textfield by Serializing the data and displaying it as an XML?How to do that too?
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Jan 16, 2012
I'm trying to check if a variable has been defined as a nullable Guid. eg.
Dim myGuid As Nullable(Of Guid) or Dim myGuid As Guid?
It seems doing a myGuid.GetType returns the underlying type, that is type Guid, not Guid?. So testing myGuid.GetType Is GetType(Guid?) always returns False.How do I find out if myGuid is a nullable type?
Ed: I can do the following, which correctly returns True for "Guid?" and False for "Guid":
Not Nullable.GetUnderlyingType(GetType(Guid?)) Is Nothing
The problem is that I don't know how to retrieve the nullable type from the variable itself, in order to test it. I've only been able to get the underlying (non-nullable) system type.
I've written a db helper function. I pass it an object comprised of public members, representing the row data of a table. The members are the table columns.Using reflection, I loop through these public members to create an INSERT statement for a command object and populate its parameters with the values in those members. So far so good.But now there's a table which has a uniqueidentifier column which I must not populate from the row object, as it defaults to "NEWID()" (using SQL Server 2008). Instead of skipping all Guid columns, which would be easy, I only want to skip ones defined in the row data class as "Guid" (non-nullable).Basically, I'm using the Guid? (Nullable) type to indicate it's ok to populate that uniqueidentifier column with data. If it's non-nullable, that tells me to skip it because the column has a NEWID() default value.
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Nov 7, 2011
I have several records in a database that have Start and End Dates
09/15/2011 - 09/30/2011
10/15/2011 - 10/22/2011
11/01/2011 - 11/15/2011
When user stores a record, I need to make sure dates don't overlap.My simple code checks date ranges within a specific record (e.g. user enters 9/16/2011 or 10/21/2011, I throw an exception.)But, on the slim chance a user gets creative (e.g. 10/14/2011 - 10/23/2011 or even 10/14/2011 to 11/16/2011), now they have circumvented my check.BTW, the user could enter 10/14/2011 to 10/23/2011 if they were editing the record that contained values 10/15/2011 - 10/22/2011.So, I'm trying to solve this riddle with a linq query. However, what I have isn't working exactly right.
UPDATE Nevermind about code not working. While trying to provide an example to expand on Miika's repsonse, I found my answer. So, giving credit to Miika for pointing me in the right direction and posting my working code below:
Here's my code:
Private Sub CheckForOverlap(myMonth As Messages.MyMonth)
Dim am As New MyMonth()
Dim amCollection As Messages.MyMonthCollection
[code]....
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Nov 24, 2010
Is there a tool in the toolbox that i can use that replaces checkboxes. i have limited amount of space and checkboxes just keep taking up room. I need the user to select multiple objects like checking multiple checkboxes.
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Jul 27, 2010
I am new to VB.Net and I'm a little confused why this line happened to be valid in VB:
DataGridView1.DataSource = ds.Tables("Customerslist")
DataSource is of type Object while Tables("Customerslist") is of type DataTable. How will I know what types of objects can be assigned to the Datasource property?
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Jan 18, 2012
In my ASP.Net Web-Application, I'm getting this error: Conversion from type 'DBNull' to type 'Boolean' is not valid.
[Code]...
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Jan 15, 2009
I created a Class which inherits Combobox and the listview is added . Now what I need is once the user click listview, the listview has to close and the clicked item has to added with combobox text. simply can say combobox1.text = listview.item(0).textFor closing & displaying the listview I need to handle the events. For
My Codings :========Public Class Combu_lstviewInherits ComboBoxPrivate treeViewHost As ToolStripControlHostPrivate Shadows dropdown As ToolStripDropDownPublic mylistview As New ListView
Public Sub New()mylistview.BorderStyle = BorderStyle.Nonemylistview.View = View.Detailsmylistview.HeaderStyle =
[code].....
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Dec 21, 2009
I'm in the process of porting an old excel addin that was writen in VBA to VB .NET. The Excel addin interacts with a number of external com objects. The code sorta looks like this:[code...]
What I'm trying to do is read the string from the COM object and get it in durr for use later in my program.
That second line results in the exception posted above. If I try casting with CStr/CType I get the same exception.
The visual studio watch window reports the type of hurr.getString as a "System.__ComObject" whereas the VBA watch window reports the type as "Variant/Object/String".
Microsoft.VisualBasic.Information.TypeName(hurr.getString) says the type is "String".
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Jan 28, 2010
Is there a way to attach a Sub or Function to an event of many controls at once?For instance, to clear a bound combobox I use this routine on the KeyDown event of the combobox:
VB
Private Sub MyComboBox_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles cboID.KeyDown If e.KeyCode = Keys.Delete Then sender.SelectedIndex = -1 End IfEnd Sub
But if I have many comboboxes, I have to copy the same routine over and over to all of them...Is there a way to attach the routine to the KeyDown event of all comboboxes?
Pseudocode example:
VB
Sub AttachEventOnKeyDown For Each ctl As Control In Me.Controls If TypeOf (ctl) Is ComboBox Then ' On ctl.KeyDown execute "MyDeleteRoutine(ctl)" End If NextEnd Sub
How can this be done?
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May 8, 2011
I've tried posting this to a few forums, even microsoft... Hopefully this forum is the place to be.
I'm programming an application in Visual Studio 2010, namely in VB.net. I have been developing an application which uses a derived class inherited from TreeView, with the aim of putting custom objects on the nodes. The method I have been using is to have a variable array against the node (of type object) which contains variables in custom classes to contain each of the variables associated with the node.
The two problems I had to overcome were, how to serialize a TreeView, and how to serialize an array of objects (of variable type). Good thing is I overcame both of these with some work of some other folks (and 3 days of my own work).[code]....
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Jan 27, 2010
lets say I have:
arecord.name = "A"
arecord.value = 15 ' a number of type "long"
'
I then
call records.add(arecord,arecord.name)
' so far, so good but lets look at the next record
arecord.name = "B"
arecord.value = "this is text" as opposed to a number of type "long"
'can I then
call records.add(arecord,arecord.name)
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Mar 22, 2010
i have a list view that contains files i use a for statement to go with them to and check what format the file is then sets its image but i dunno how to get it to work i cant use the or statement it says it cant convert to boolean
vb
If Label1.Text = "doc" Or "docx" Then
oresults.ImageIndex = 14
ElseIf Label1.Text = "ppt" Or "pptx" Then
oresults.ImageIndex = 10
End If
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May 14, 2010
I am currently using the following code to parse a webpage.
CODE:
Where it has:
CODE:
It would work, as with this:
CODE:
But i need it all in one line of code..
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Mar 11, 2010
my code is :
[Code]...
The error is Value of type '1-dimensional array of string' cannot be converted to 'String'.
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Jul 30, 2011
Given an object instance, how can I recurse its members (i.e. the whole object graph) for an object of a specific type, or one that inherits from a specific type?
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May 16, 2011
I am developing a VB.NET application with SQL Server 2008 and I get the above error when I try to run this ASPX file. What is the cause?
[Code]...
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Jul 7, 2010
I am trying to figure out how to check a string can contain a certain value.In the begining I had a checkbox and wanted to hide a ceratin field depending upon which checkboxes were selected.The problem with this is that the value is always = to the first value.
I got around this by writing these values into a hidden textBox and using a loop.So now I have a textbox and if the user selected the 1st and 3rd choice the textBox would = "AC" If they selected all choices it would = ABCD etc...How can I determine if the values in my textBox contains just letter 'B' ?
I tried this:
--------------------------
Dim values As String = [String].Empty
For Each item As ListItem In section2List.Items
If item.Selected Then
[code]....
but this doesn't work.
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Jan 12, 2011
What's a sound approach to override the CompareTo() method in a custom class with multiple approaches to comparing the data contained in the class? I'm attempting to implement IComparable(Of T) just so I have a few of the baseline interfaces implemented. Not planning on doing any sorting yet, but this will save me down the road if I need to.
Reading MSDN states mostly that we have to return 0 if the objects are equal, -1 if obj1 is less than obj2, or 1 is obj1 is greater than obj2. But that's rather simplistic.
Consider an IPv4 address (which is what I'm implementing in my class). There's two main numbers to consider -- the IP address itself, and the CIDR. An IPv4 address by itself is assumed to have a CIDR of /32, so in that case, in a CompareTo method, I can just compare the addresses directly to determine if one is greater or less than the other. But when the CIDR's are different, then things get tricky.
Assume obj1 is 10.0.0.0/8 and obj2 is 192.168.75.0/24. I could compare these two addresses a number of ways. I could just ignore the CIDR, and still regard as obj2 as being greater than obj1. I could compare them based on their CIDR, which would be comparing the size of the network (and a /8 will trump a /24 quite easily). I could compare them on both their numerical address AND their CIDR, on the off chance obj2 was actually an address inside the network defined by obj1.
What's the kind of approach used to handle situations like this? Can I define two CompareTo methods, overloaded, such that one would evaluate one address relative to another address, and the second would evaluate the size of the overall network? How would the .NET framework be told which one to use depending on how one might want to sort an array? Or do some other function that relies on CompareTo()?
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Jun 17, 2009
If Double.Parse(list_numbers.Item(i), possibledouble)
list_numbers is a list of strings
list_numbers.Item(i) = "0.000"
possibledouble is a double
debugger returns "input string was not in a correct format"
i thought that the double parse would convert the string into a double format of "0.0" but it gives me an error.
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Dec 21, 2011
i have a textbox in a calculator and i want an if function so that it checks that there cannot be 2 .'s in it:[code]
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Mar 22, 2010
I'm trying to add a new record to my database but i keep getting the message - "conversion from type DBnull to type string is not valid". I think its something to do with the Employee ID when VB attempts to save it to the database my code is below
Imports System.Data.OleDb
Public Class Add
Private Sub DisplayRow()
[Code]....
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May 25, 2011
I now have SQL Parameters set up and I'm using them to save/delete/add my data. This all works well, except when it's trying to save a combobox to the datatable it appears with the error above.Majority of my comboboxes have datasources, and the valuemembers of these are the actual list items, not the ID's of the list items.I'm not sure why this error could be happening, I'm fairly sure I've connected everything to the binding source correctly; I've checked it a few times.Does anybody know what the cause of this could be? I've looked around a bit and I haven't found much
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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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Mar 19, 2009
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]
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May 16, 2007
I have these errors when creating my website?
Error 1Server Error in '/ Application. -------------------------------------------------------------------------------- Conversion from type 'DBNull' to type 'String' is not valid. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid. Source Error: Line 64:
Line 65:
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