.net - LINQ Casting With A Data.DataTableCollection?
Aug 18, 2010
I have the following VB.NET code that I am using to sort a Data.DataTable by column count.
For Each dtTarget As Data.DataTable In _
From x In Target.Tables _
Where DirectCast(x, Data.DataTable).Rows.Count > 0 _
Order By DirectCast(x, Data.DataTable).Columns.Count
...
Next
Is there a way to indicate that x is a Data.DataTable without having to DirectCast it each time it is referenced (twice in this case) in the LINQ query?
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Dec 5, 2009
I have one question. i have seen some codes like:
Req = CType(System.Net.HttpWebRequest.Create("url"), Net.HttpWebRequest)
Is it really necessary to cast the same type, or is there a difference when its not casted.
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Oct 21, 2009
How can I convert an object of type System.Data.Linq.DataQuery to System.Linq.IQueryable?I'm working with Visual Basic/Silverlight, and the source code of my query is as follows:
Public Function Get_Cli_Pag() As IQueryable(Of V_Cliente_Pagare)
Dim Qry = From P In Me.Context.Pagares Join C In Me.Context.Codigos On C.Codigo
[code]....
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Apr 9, 2010
I have three tables in SQL server which I would like to show and access on a form. Table 1 contains account data, address, contact details etc. Table two contains data attached to a Person, tel no , Mobile no, Email etc. Table three contains details on what awards the person holds, i.e. one person can hold several awards.
Therefore I have a one many relationship between the first two tables and a one many relationship between the second two tables. This is set up in SQL
The first two tables are shown on a form, table 1 via a set of text boxes, table 2 via a datagrid control.
I would like the functionality whereby I could select a row in the datagrid showing the persons name and find the Persons_ID number then use that as a filter to a second datagrid view so that only the selected persons awards show in the datagrid.
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Mar 13, 2009
I have the following problem with MEF: Interface definition to be used by host:
Public Interface IExecuteDoSomething
Inherits IAddinSettings
Event DataReceived As EventHandler(Of DataReceivedEventArgs)
Function DoSomething() As Boolean
End Interface
[Code]...
Everything seems to work fine until the Button2_Click routine is executed, then an InvalidCastException is thrown with the info:Unable to cast object of type 'System.Collections.Generic.List1[SharedLibrary.IExecuteDoSomething]' to type 'System.Collections.Generic.List1[SharedLibrary.IAddinSettings]'.
How can i solve this problem, because the imported object implements both of the interfaces?
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Dec 9, 2009
The next code works fine in C#:
[Code]...
But this code crash with a OverflowException in VB.Net.
[Code]...
Both codes seems the same to me. What is the difference and how can I get the C# code converted to VB.Net?
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Aug 19, 2011
I have a object type variable (control .Tag) that I need to cast to a structured type, and change a member in. This is a contrived but representative example
[code]...
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Oct 16, 2009
get around this. I have a data base field that is a decimal data type and I want to display it in a text box with the following txtWeekdayRate = CType(RoomsDataRow!WeekdayRate, TextBox)I get the following error when I run my program.Unable to cast object of type 'System.Decimal' to type 'System.Windows.Forms.TextBox'.
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Mar 1, 2009
I am getting the followin error from my code. System.InvalidCastException was unhandled Message="Unable to cast object of type 'QADBASE.DMRDataLists' to type 'QADBASE.DMRData'." Source="QADBASE" I am getting the error in the code below on the createDMRIssue
[code]...
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Dec 31, 2009
I got a weird problem here like I got a site that users can post comments on a friend profile page.Everytime a user post a comment my application sends e-mail to that page owner, you know to inform for a new posted comment on his/her profile page.The problem is I want to stop the application from sending email if that user has just recently posted a comment say like 5 hours ago/earlier.Here is the function I use that would try to check it:
[Code]...
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Dec 6, 2010
I am trying to extract some data from a website using a LINQ statement, the XML is in the following form.
<parent>
<p>
<b>
Title
</b>
[code]....
I would like to get the As Of Date and Data (the data row is iterated several times). Also the table and as of date appear several times in the document (the table is active from a date).I can get the rows using the following LINQ but how do I get the As Of Date
Dim l_PricesTable = From rows In l_Xml.Descendants("tr") _
Where ((rows.Descendants("td") IsNot Nothing) AndAlso (rows.Descendants("td").Count >= 1)) _
Select Data = rows.Descendants("td")(0).Value,
AsOfDate = ???
I have no way of changing the XML as it is a 3rd party source. There is no XML element which contains just the as of date and also the table, they are all under the one parent node.
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Jan 27, 2012
I have the following line of Dim clients = From client In db.clients Select client Where client.ClientID = id
In debugging, the clients object populates perfectly, but how can get get data from the clients object? Like if the clients object has a FirstName property, how can I set a textboxes text property to that property from the clients object?
I thought it'd be something like:
tbClientFirstName.Text = clients.FirstName But that doesn't work.
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Aug 1, 2011
I need to update a datatable using LINQToSql. Option Strict is ON. Datatable name is Customer with fields customerID, customerName, SalesID. I need to update rows with SalesID = -1.
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Apr 28, 2011
I have this XML:
<root>
<data name="lnkViewResultResource1.Text" xml:space="preserve">
<value>bekijk de resultaten</value>
</data>
[code]...
But, unfortunately, it is not working, it is not getting anything.
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Apr 20, 2010
Public Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T)Return DirectCast(data, GenericType(Of T))End Function
The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T?
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Jan 12, 2011
I have an Entity class which Implements IWeightable:
Public Interface IWeightable
Property WeightState As WeightState
End Interface
I have a WeightCalculator class:
Public Class WeightsCalculator
Public Sub New(...)
..
End Sub
Why can I not do wc.Calculate(entities)? I receive:
Unable to cast object of type
'System.Collections.Generic.List1[mynameSpace.Entity]'
to type
'System.Collections.Generic.IList1[myNamespace.IWeightable]'.
If Entity implements IWeightable why is this not possible?
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Mar 11, 2011
I am passing Date Field to SQL Database. Field is declared as String in the VB.Net Application. I wrote a piece of code for casting to Date
[Code]...
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Apr 14, 2009
I'm a C# programmer who is forced to use VB (eh!!!!). I want to check multiple controls state in one method, in C# this would be accomplished like so:
if (((CheckBox)sender).Checked == true)
{
// Do something...
[code]...
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Apr 27, 2012
I have tried everything to no avail. I need to cast the value from a user selected dropdownlist to another dropdownlist on another page. The data in the textboxes are a series of numbers. Also is there a way to display the value in the second dropdown list as well as other values? For example, my dropdown has the values 1-6, user selects 4, which displays first in the dropdown on page 2 but the other values also display in case they want to change there selection??
If Not Page.PreviousPage Is Nothing Then
Dim table As Control = PreviousPage.Controls(0).FindControl("table1")
Dim ddl As DropDownList = CType(table.FindControl("ddlB_Codes"),c DropDownList)
[code].....
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Mar 1, 2010
I'm trying to obfuscate some VB.NET 2003 app.The resulting assemblyes are obfuscated and "run" with some errors.I cleaned all potential reflection problems, but I'm not being able to read the selected value of a combobox.
I load the Combobox using their Datasource properties, using a collection of "VTPair" (a class created by me with 2 properties: one of string type and other of object type to store the value)
This combobox handle pairs like "Male | M" or "Female | F".When trying to see what is selected, I use if mycombo1.SelectedValue = "M" then.This code, after obfuscation, throws me an exception that cannot cast type "XX" to string "M".
So, I changed the code to something more correct, explicitly casting the selected value to String:
if ctype(mycombo1.SelectedValue,string) = "M" then But the error is the same.Debugin my original code, the SelectedValue property is of type "Object" but it is a string.I tried using the ComboBox.SelectedItem property that is also an object but this time what is inside is of type "VTPair" (my own class) and then trying to access its "Value" property (which is of type Object) and trying to cast to string fails again.
Does anyone have an idea to "translate" this piece of code to work OK after Dotfucate it?
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May 14, 2010
I have an object that inherits from an interface. I can create and return the following:
Dim o As IRequest
o = New Request
Return o
This works fine. Now I want to return a List(Of Requests), so I try the following:
Dim o As List(Of IRequest)
o = New List(Of Request)
Return o
The error below is being given on o = New List(Of Request)
System.Collections.Generic.List(Of MyObjects.Request)' cannot be converted to System.Collections.Generic.List(Of MyInterfaces.IRequest)'.Consider using 'System.Collections.Generic.IEnumerable(Of MyInterfaces.IRequest)'
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Nov 4, 2010
I don't know where it thinks I'm casting.
Here is my property
''' <summary>
''' Gets the GetX509Certificate from a file.
''' </summary>
[Code]....
and heres where it says im doing the illegal cast:
Dim cert As System.Security.Cryptography.X509Certificates.X509Certificate2 = Me.GetX509Certificate
Why is it saying that? Everything is defined in the right type but it still thinks I'm casting.
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Apr 20, 2012
in vb, you can use text which is in textbox instead of numerical expressions. I mean, if I write 50 in textbox1 and also I can write like that code:
Dim result As Double = TextBox1.Text + 0.4
as you see, I didnt convert any type but it works in vb.net
But I want to learn what are disadvantages of this using?
(I am just talking about arithmetic operations)
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Jun 22, 2009
i have a property (items) that i want to use for either a checkedlistbox or a standard listbox depending on the value of another property.
heres the code i wrote that doesn't work:
[Code]...
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Nov 14, 2010
Say I have a interface called IProperties and I have a collection called colMyProperties that is a collection of IProperties. Then I have an object called clsProperty that implements the IProperty interface. Now, in my code where I add objects to the colMyProperties collection I add a bunch of clsProperty objects. so far so good.
Now when I try to access an object in the collection I can only access properties and methods of the IProperties interface, not the clsProperty object. What am I doing wrong? Do I need to cast the object?
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Sep 4, 2009
I usually avoid VB's built-in conversion functions (CStr, CDate, CBool, CInt, etc.) unless I need to do an actual conversion. If I'm just casting, say from an object to a string, I normally use either DirectCast or TryCast, under the assumption that CStr, etc., are doing some extra stuff I don't need. But sometimes the DirectCast syntax is a little cumbersome, as in the following example.[code]SqlDataReader.Item returns an Object, which needs to be cast to a String. CStr is easier to read, type, and explain (IMO). My question is, does it matter which one I use? Should I just go with CStr (and CDate and CBool, etc.) and not worry about the extra work I assume those functions are doing? Is there any other downside to using these functions?
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Feb 28, 2012
i have the following code which walks through an Excel file and this works fine note that the following line does work well (folder is being set earlier in the code)
[Code]...
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May 14, 2009
When I have many controls on a Form (i.e. Label, Button etc) that do almost the same thing, I often use one method to handle all the controls Click, MouseDown, MouseUp events.But to know which of the controls throwing the event and access the properties of that control I need to cast the "sender" object to the correct type.
The thing is that I always know which type it is, I don't really have to "TryCast", "DirectCast" and check if the operation returns true. I some times use CType as well.
[Code]...
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Jun 18, 2009
Delegate Sub UpdateTextHandler(ByVal recbuffpass() As Integer)
Private Sub someSub()
Dim f As frmMain = My.Application.OpenForms("frmMain")
f.Invoke(New UpdateTextHandler(AddressOf f.UpdateTextMethod), New Object() {recbuf})
[code].....
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Sep 30, 2009
I've got a project called Service.Inside the project, i've got 2 windows classes.ClassA is the main windows class which opens up when I run the program.On ClassA, I've got a button which, when I click it, opens up ClassB which is the other windows class. Inside the button's eventhandler (click), I've got a string which contains the name of ClassB's class ie "ClassB". I will probably get this from a table. Is it possible to initiate the object ClassB without using if statments to check what the type of object is. In the code below, i've managed to create a o of type object, but i need to new it with the ClassB
vb.net Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
[Code]...
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