VS 2010 Determine Type In Collection In DataSource?
Sep 7, 2010
I am customizing a DataGridView control. The DataGridView is supposed to be bound to a collection of some type (be it a List(Of T) or ArrayList or whatever), and the idea is that one can easily determine (at design-time in this case) which properties of the type have to be shown in the grid and which column header name they should get. One can do this using an attribute. For example, if I have a class Person with Name, Age and HairColor and I don't want to show the HairColor property, and want to show the Name property as 'Person', I would use:
vb.net
Public Class Person
<Grid.GridOptions(displayName:="Person", visible:=True)> _
Public Property Name As String
[code]....
I do this during run-time by simply looping through the properties of the bound type (in this case Person), retrieving the GridOptions attribute (if any) and checking the values provided. This works just fine except for one thing: I'm not really sure how to determine the type in the databound collection...
At the moment, I cast the DataSource property to an IList and retrieve the type of the first instance in that list (if any). If there isn't a first instance (the list is empty) then I don't know how to get the type... Often I know that it will be impossible to know the type. If someone is binding an ArrayList for example, then it's impossible to know what kind of items he's going to put in that ArrayList. Even the normal DataGridView cannot show any columns when databound to an empty ArrayList. However, the framework's DataGridView does show the columns when bound to, for example, an empty List(Of Person), or a Person array.
I'm pretty sure that casting the DataSource to an IList is not the correct way as all information about the type of items in that list is then lost. But I'm not sure what else to cast it to... ITypedList? IBindingList? I even considered List(Of T) because that's all I am going to be using, but besides the fact that the grid would then obviously only work for a List(Of T) I still don't know how to do this... I don't know 'T' so I can't cast it to a List(Of T)...
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Oct 28, 2009
I can't figure out how to determine the type of an object in a collection. I want to do a For Each ... Next loop over the items in the DropDownItems collection of a ToolStripMenuItem. For those items that are ToolStripMenuItems themselves I want to take some kind of action. (The collection can contain other types of items, such as ToolStripSeparators). So I need to say something like: If Typeof(item) = ToolStripMenuItem Then .
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Oct 9, 2009
I have a small piece of code that iterates through the controls collection on a panel (below) Everything works fine until I want to focus on a control that doesn't support the selectall method i.e. a datetimepicker. Is there any way of determining the type of control and not call the selectall method when the type is datetimepicker. All my other controls support it so that's the only one I need to exclude.
[code]...
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Aug 26, 2011
Like i want it to read the lines i have in the text file but i get an error Each time i press the button Why?
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim objreader As New System.IO.StreamReader("C:UsersJamesDesktopMusicas.txt")
Do Until objreader.EndOfStream
[code]....
Error:
Quote:
Items collection cannot be modified when the DataSource property is set.
Error line
Quote:
ListBox1.Items.Add(objreader)
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May 22, 2010
I want to create some type of list or collection. Each item on this list or collection will need contain A string name and a integer value. Something like
[Code]...
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Feb 19, 2012
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]....
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Apr 5, 2011
I have a 2 classes, one is Employee, the other is Employees. Basically Employees is a collection of Employee, I have a combo box where the Datasource is Employees.
When the user selects a value from the combo box, How do I get an Employee object from whatever is selected?[code...]
It is an Infragistics combo box by the way.
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Apr 21, 2009
I have two combo boxesthat use the same collection for their datasource. The data member and value member are also the same properties. When the form loads, and I select an item in one of the combo boxes, the same item is then selected in the other combo box. I want the combo boxes to work separately. Do I need to have two different collections, even though they would have the same data in them?
cboInboardKnife.DataSource = cKnives
cboInboardKnife.DisplayMember =
"Name"
cboInboardKnife.ValueMember =
"ToolID"
cboOutboardKnife.DataSource = cKnives
cboOutboardKnife.DisplayMember =
"Name"
cboOutboardKnife.ValueMember =
"ToolID"
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Aug 3, 2011
I have a custom collection which is derived from a base class implementing IEnumerable and IEnumerator, this collection is populated with custom objects.I'm trying to set the datasource on a ComboBox on a WinForm to use the above collection - but when the code is run the ComboBox is always empty.
The code I was using was this:
Private Sub ViewSources_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
' declaration
Dim sourceCollection As SourceCollection
Dim source As Source
[code]....
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Apr 27, 2010
I am trying to refresh my combobox when an item is selected and added the highlighted code as shown below; [code]Items collection cannot be modified when the DataSource property is set.
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Jun 17, 2010
I have a combobobox on my form, and I use the following code to populate the data from SQL Server:
cbname.DataSource = DSAssetName.Tables(0)
cbname.DisplayMember = "IDWLNAME"
cbname.ValueMember = "FIDWID"
[code].....
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Feb 13, 2010
I have two tables "Person" and "Alias" in a one to many relationship. I have a DGV for "Person" and want to use a combobox for the Aliases. I also have a textbox and a button for the user to type the alias name and click the button to add the alias name to the combobox and update the dataset. I keep getting the "Items collection cannot be modified when the DataSource property is set." Error. But if i use a DGV instead of a combobox for aliases, I have no errors and everything works fine. If I remove the datasource property for the combobox it will not get populated with the data already entered, so how, or can I, set it up where the combobox gets populated when the form loads and able to add items to the combobox????
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Dec 15, 2009
When I try to add new datasource, the option 'database' isnt shown. Only Service, Object and Sharepoint is shown. This is done in VS 2010 Beta 2
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Dec 16, 2011
I am trying to make it so when I use Me.Controls("Timer1") for example I can access specific commands for a timer such as Stop() Start(), I tried CType() and typed in "Timer" as the type but it says the control type can't be converted to the "Timer" type.
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Nov 5, 2011
Public Shared Function IsType(ctrl As Control, ByVal thisType As ??????) As Boolean Return (TypeOf ctrl Is thisType) I need a function that I can call, for example, to determine if a control is type RichTextbox.dim z as Boolean= IsType(txtBox1, RichTextBox) I ned to determine if a control is a given type (i.e., not always RichTextBox). I don't know what Type to make thisType. Can this be done?Actually I simpified the problem but if the above is answered I can write the function
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Apr 28, 2012
I want to scan a directory and see what files are NOT bmp image files. As the file extension can lie I need to interrogate the file itself. I found some code here [url]...?ID=112 that does exactly this however it was written for VB5 and is 13 years out of date! I tried compiling it however VB 2010 baulked and I don't have the expertise to make it work.
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Jul 31, 2009
How can I programatically determine if a file with a certain extension (XLS, for example) is really an Excel file and not a VBS file, for example, that has the XLS extension?
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Dec 12, 2009
I need to determine the type of a WinForms control in a collection.
[Code]...
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May 17, 2010
how do you determine cell type of a column?
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Oct 14, 2010
I need to check a value within the registry. The application (Cisco VPN) is a 32bit app so uses Wow6432Node when installed on 64bit operating systems.What would be the best method of selecting which string to use? Checking the OS for x64, attempting to read one and then the other if the first fails? Or is there a better method?
Dim keyName64 As String = "HKEY_LOCAL_MACHINESoftwareWow6432NodeCisco SystemsVPN Client"
Dim keyName32 As String = "HKEY_LOCAL_MACHINESoftwareCisco SystemsVPN Client"
Using .net 4.0 framework?:
Dim registryKey As RegistryKey
If Environment.Is64BitOperatingSystem = True Then
registryKey = registryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64)
Else
registryKey = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32)
End If
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Jul 31, 2011
I am converting a VB.Net application to C#. Everything else is going great. Except this bit. I have a function which builds menus,sub menus and seperators from a database. It can build a MenuStrip or a ContextMenuStrip which can then be assigned to a form.
This means that menus can be extensive and conpmex but managed outside the application, which I also use as part of my security access model. All menus are controlled from the database externally, it also means I can develop visual tools (Treeviews etc) to manage user menus. The application uses menus extensively which is by design.
Programmatically I want to assign an eventhandler to every item that isnt a dropdown or a seperator
In VB I would do this, (works perfectly)
[Code]...
"System.Windows.Forms.ToolStripItem' does not contain a definition for 'DropDownItems' and no extension method 'DropDownItems' accepting a first argument of type 'System.Windows.Forms.ToolStripItem' could be found (are you missing a using directive or an assembly reference?)"
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May 19, 2009
I am still developing this function, but here is what I am intending it to do. This function will accept an Object, then try to determine its type. There are a specific set of types I am looking for: Integer, Boolean, Date, String. What I have so far is pretty privative, but it seems to be working so far:
Private Function DataType(ByVal entry As Object) As ValueType
Try
If IsNumeric(entry) Then
[Code].....
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Mar 27, 2010
I have a class C(Of T). I want to determine if some given value has type C, regardless of what T is. For example, I might want to determine if a value is a strongly-typed list, regardless what type of items the list stores. I just need to know how to do it in VB.net. In Java the syntax is like this:
var result = obj instance of Gen2<?>;
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Jun 24, 2011
I am developing a VB.NET ASPX file and am trying to run a string query in VB.NET, but now I get the above error message. How can I determine the cause? Some of the code in this
[Code]...
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Mar 3, 2011
I have the following VB.NET function, for example:
Public Function MyFunction (Of TData) (ByVal InParam As Integer) As TData
End Sub
How do I, in a function, determine if TData is a NULLable Type?
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Mar 17, 2010
I have a dataset and want to know the data type of a specific column. The GetType returns datacolumn not string or integer etc.iggy!
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Sep 24, 2009
I'm interested in having a generic 'Try Catch' clause, with some case statements or if/than statements within the Catch part so that I can handle different error types differently. some way to get ex.Errorcode or ex.ErrorType that differentiates the different errors to a unique value.
How can this be done?
Try
'some code taht will throw an error'
Catch ex AS Exception
If ex.ErrorCode = 20 then
' Do something'
[Code].....
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Dec 14, 2006
I have the following VB.NET function, for example:Public Function MyFunction (Of TData) (ByVal InParam As Integer) As TDataEnd Sub
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Nov 25, 2011
Heres my sub:
Dim onThisTable as String ="Name"
Private Sub skill_mouseHover(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.MouseHover, button2.MouseHover, panel1.MouseHover, panel2.MouseHover, pbox1.MouseHover
[Code]....
Now I wish to give onThisTable a different value depending what the user pass over (panel or a pbox or a button) but I cant find what is the correct way to compare what type it is ...
Private Sub skill_mouseHover(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.MouseHover, button2.MouseHover, panel1.MouseHover, panel2.MouseHover, pbox1.MouseHover
[Code]....
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Nov 14, 2010
I've created the following basic function to determine whether specific control type is currently loaded:
Private Function IsPreviewerTypeLoaded(Of T)() As Boolean
For Each previewer In LoadedPreviewers
If previewer.GetType().Equals(T) Then
[Code]....
I need to compare each control against the generic type supplied. Equals(T) fails to do the job, producing a compiler error. How to make it correctly?
UPDATE: is the following correct?
previewer.GetType().Equals(GetType(T))
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