LINQ To EF Sum Function Error When No Records Returned
Jun 1, 2012
Have seen some solutions for C# but do not know how to solve the issue in VB.NET.
Query:
Dim Query = (From t In myEntities.Bookings
Where(t.Ref = Someid)
Select t.People).Sum()
t.Ref field is an Int and so is t.People.
The SomeId value is the primary key of the related table. This issue is that there will not always be records in the Bookings table with a Ref value of Someid - so the query throws the following error.
I have seen others have got around this problem with catching the error, but from reading up on this and as per the error information it seems there should be a solution (in VB.NET) to cast the query or some of the fields in the query to nullable types?
Error is as follows:
The cast to value type 'Int32' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.
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Jun 29, 2010
I'm trying to use a nested multi-line lambda Function in VB.NET and am getting an error. Here's what my code looks like:
cartItems = cartItems.Select(Function(ci) New With {.CartItem = ci, .Discount = discountItems.FirstOrDefault(Function(di) di.SKU = ci.SKU)})
.Select(Function(k)
If k.Discount Is Not Nothing Then
[code]....
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May 23, 2012
VS 2010, VB.NET, WINFORMS. In my app i have a need to import foxpro database tables and exclude the deleted records. The problem is that FOXPRO tables keep deleted items inside the same table. I have tried using DELETED=NO in the connection string but vb throws "Format of the initialization string does not conform to the OLE DB specification."
My function is as follows:
Dim _DBConn1 As String = "provider=vfpoledb.1; Data Source = " & file1 & ";DELETED=NO"
Dim _DBConn2 As String = "provider=vfpoledb.1; Data Source = " & file2 & ";DELETED=NO"
Dim _DBConn3 As String = "provider=vfpoledb.1; Data Source = " & file3 & ";DELETED=NO"
Google results pointed me in the direction of DELETED=NO but its throwing that exception error now that I have added it..
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Feb 6, 2011
When I query a DataTable using LINQ, are the rows returned as references? Either way, is it possible to control this behaviour, so that rows are either returned as references or as new rows?My guess is that all objects are returned as references by default, since that seems to be the normal behaviour in most programming languages.
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Apr 4, 2012
How to give another function's returned value in LINQ.[code]but in above query I should write code to store the return value of GetObjProperty Value(p) and add obj-p and returnValue combination to the dictionary.The last line below code is wrong. but please suggest me how to correct it. My intention is, I want output collection(say dictionary) of each fruitname and its color(returned by other function call) for all the fruits which the GetFruitColor is not nothing(it can be empty or valid string).[code]In above code last line is wrong. So how to put getFruitColor in k, how to correct it to save the k value and give me output as dictionary of fruit and k value.
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Sep 5, 2010
Why this code doesn't work? It returns an unexpected value actually total = 0.
total = Cscore(TextBox1.Text) * CDbl(TextBox2.Text)
When trying this
total = TextBox1.Text * TextBox2.Text
It returns the expected value but I need to pass textbox1.text to the function to get the desirable value
The function is this
Public Function Cscore(ByVal score As Integer) As Double
Select Case score
Case score = 100
Return 5.0
Case score >= 95
[Code] .....
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Apr 2, 2011
I have many functions that perform mathematical calculations.
Here is one for example:
Public Function internaldiamofcasingpipecalculation(ByVal Externaldiameterofcarrierpipe As Double, ByVal insulationthickness As Double) As Double
[Code]....
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Feb 22, 2010
I'm new to VB.NET and want to parameterise the SQL Connection Strings in my VB.NET App. I've added a function to my Main Form to retrieve the App.config File like:
Imports System.Configuration
Imports System.Configuration.ConfigurationSettings
Public Class MainMenu [code]....
In my other forms when i want to reference the Connection String, i get an error saying getConnStr is not declared?
Private Sub UpdDept_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
myconnection = New SqlConnection(getConnStr()) <=============
Dim mycommand As New SqlCommand()
why i get this when i've declared the Function as Public?
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Mar 18, 2009
When the AlertsSettings.xml is not present the Appsettings is assigned to nothing. The variables that follow that definition rely on the existance of that information which will normally be set by the load method. But when there is a problem and either of the variables do not get a value how do I handle that in the code that relies on those values. The Settings class deserializes an xml document and assigned values to properties.
Sub Main()
Dim Appsettings As Settings = Settings.Load("AlertsSettings.xml")
Dim AlertsServer As String
[Code].....
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Aug 5, 2011
This should be a fairly common question, but I haven't found a straightforward answer anywhere.
If I instantiate an object within a function in VB.NET and return it, does it return it be reference or by value. IE - should I be worried about performance if I write something like this:
Public Function ret_obj_func() As big_object
Dim ret_obj As New big_obj(<lots of stuff>)
Return ret_obj
End Function
If I call this function from somewhere else, will it instantiate the object in the ret_obj and then create a deep copy to pass back a copy to the caller, Or will it just pass back a reference?
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May 2, 2012
I'm trying to establish a connection to my SqlDatabase while getting the connection string from a function. This will eventually lead to dealing with the appconfig file, but for now I'm just getting the basics established.
Imports System.Data.SqlClient
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[code]....
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Jul 2, 2009
Combobox with bound rowsource, but I want to change the displaymember to a string returned by a procedure. In Access/VBA I would have a little function to build the string, then simply code the recordsource of the cbo as:
"SELECT ClientIDS, fnGetName([ClientIDS]) AS ClientName FROM tblPerson ORDER BY fnGetName([ClientIDS])".
Pretty straightforward, but I've messed around with this for hours in VS2005/VB to no avail.SELECT ClientIDS, fnGetName
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Feb 25, 2009
I have a 2 dimensional array of groupboxes that I use to populate a form setup so the first indice is a tab number and the second is the groupbox number.The user can dynamically add tabs to the tabcontrol but I need to add and populate groupboxes to the new tabpage and I can use existing groupbox data in the array for default values.I understand I have to code a deep clone of the source groupbox as it has textboxes in it so I want to add a cloneGBox function that returns a new, populated groupbox when I pass in the x,y indices for the source groupbox in my array.
dim gbx as groupbox = cloneGBox(x,y)
and code cloneGBX as
public function cloneGBox (byval x as integer, byval y as integer) as groupbox
[code].....
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Sep 2, 2009
I am trying to upload a file to Mainframe machine from my VB.net application. I am getting the following error.The remote server returned an error: (501) Syntax error in parameters or arguments
[code]...
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Jan 11, 2011
Using vb.net 2005 - FtpWebRequest for ListDirectory always gets 550 error The remote server returned an error: (550) File unavailable (e.g., file not found, no access).
On both FTPListDirRequest.Method = System.Net.WebRequestMethods.Ftp.ListDirectory
FTPListDirRequest.Method = System.Net.WebRequestMethods.Ftp.ListDirectoryDetails
[Code]...
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Jul 16, 2009
I am calling an Oracle function PKGDummy.F_EMPDATA using vb.net.
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Jul 27, 2010
I have the code below. The code returns a string in (IntersectingPoints) for X and Y. I need X and Y values to be in single and stored in an array to deal with later.[code]...
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Jun 17, 2010
When I tried to read the data of a http link using VB.net, an error occur. The error is:The remote server returned an error: (406) Not Acceptable.This error is only occur for some links.
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Jan 25, 2010
I have the following statement, I want to turn it into a Public Shared Function :
If isEmployee Then
Dim employeeInstance As New Employee
employeeInstance = GetEmployeeInstanceByUserId(userId)
[Code]....
Public Shared Function GetWorkerInstance(Byval isEmployee as Boolean) As ...(not sure what to write here)...
There two possible return Type. I'm not sure what I should declare for the function return type.
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Aug 5, 2011
If I instantiate an object within a function in VB.NET and return it, does it return it be reference or by value. IE - should I be worried about performance if I write something like this:
Public Function ret_obj_func() As big_object
Dim ret_obj As New big_obj(<lots of stuff>)
Return ret_obj
End Function
If I call this function from somewhere else, will it instantiate the object in the ret_obj and then create a deep copy to pass back a copy to the caller, Or will it just pass back a reference?
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Jul 14, 2009
I have a Class MessageIndex which holds an integer. I have a custom DataGridViewComboBoxCell which has a MessageIndex variable. If the MessageIndex is not set, the cell acts as a normal DataGridViewComboBoxCell; if the MessageIndex is set, then the GetValue and SetValue methods of the DataGridViewComboBoxCell are overridden so as to return the value of the object from its DataSource at the index of the integer stored in the MessageIndex.
As far as I can tell from stepping through the code, that actually works fine. The object returned by the GetValue function is fetched from the DataSource, based on the integer stored in the MessageIndex.
The problem is that when the DataGridView is displayed, all of the cells are blank. The values of the cells can then be set using the ComboBox dropdown, which appears to work fine.
But why are the initial selections not being displayed? As I say, as far as I can tell, the correct information is being retrieved by the GetValue function of the DataGridViewComboBoxCells when the form is initially displayed. It's just not ending up on the screen.
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Sep 27, 2010
When I declare two datatables and fill them both from a datatable returned by a function in class, that when i filter the one it seems to filter the other aswell?
For example:
I declare the datatable and initiate my class:
Dim DatatableOne As New Datatable
Dim DatatableTwo As New Datatable
Dim MyClass As New MyClass
I then call the function that returns a datatable and apply it to datatable1 and 2 Then fill two DataGrids with the table:
DatatableOne = MyClass.GetTable()
DatatableTwo = MyClass.GetTable()
DatatableOne.DefaultView.RowFilter = "Name = 'Tom'"
[CODE]...
For some reason i don't understand but both grids end up with the filtered data?
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Jun 28, 2009
I have two functions written in VB.NET:
1) The first function (call it GetValues()) returns values in a SQL database as a list via a stored proc. One of the fields is DateTimeSubmitted. All of this data is displayed on my webpage using a repeater control. It works fine.
2) The second function (call it NiceDate()) I created to change the DateTimeSubmitted to a nice date such as "one minute ago" or "yesterday".
My problem is I have no idea which is the best part of the process to do the conversion (at point of data extraction or in pageload etc.) or in fact how to do the conversion.
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Apr 14, 2010
I asked on SO a few days ago what was the simplest quickest way to build a wrapper around a recently completed database. I took the advice and used sqlmetal to build linq classes around my database design.
Now I am having two problems. One, I don't know LINQ. And, two, I have been shocked to realize how hard it is to learn. I have a book on LINQ (Linq In Action by Manning) and it has helped some but at the end of the day it is going to take me a couple of weeks to get traction and I need to make some progress on my project today.
Click HERE To see my simple database schema. Click HERE to see the vb class that was generated for the schema.
My needs are simple. I have a console app. The main table is the SupplyModel table. Most of the other tables are child tables of the SupplyModel table.
I want to iterate through each of Supply Model records. I want to grab the data for a supply model and then DoStuff with the data. And I also need to iterate through the child records, for each supply model, for example the NumberedInventories and DoStuff with that as well.
For the record I have already written the following code...
Dim _dataContext As DataContext = New DataContext(ConnectionStrings("SupplyModelDB").ConnectionString)
Dim SMs As Table(Of Data.SupplyModels) = _dataContext.GetTable(Of Data.SupplyModels)()
Dim query = From sm In SMs Where sm.SupplyModelID = 1 Select sm
This code is working...I have a query object and I can use ObjectDumper to enumerate and dump the data...but I still can't figure it out...because ObjectDumper uses reflection and other language constructs I don't get. It DOES enumerate both the parent and child data just like I want (when level=2).
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Nov 15, 2010
Just finished reading a book on visual basic "Imports System.IO" and "FtpWebRequest". I double checks this code and tripple checked it but I can't seem to find anything wrong with it, bare in mind I did write it from scratch with help from the book so maybe its full of mistakes.[code]
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Oct 27, 2010
I am creating an xml file with LINQ as follows...
Public Sub CreateXml()
Dim db As New MDataContext
Dim Customers = <gallery columns="3" rows="3">
[code]....
Could i mix local values with the ones returned from the LINQ query...Something like the following?
Public Sub CreateXml(ByVal **Col** As String, ByVal **Row** As String)
Dim db As New MDataContext
Dim Customers = <gallery columns="& **Col** &" rows="& **Row** &">
[code]...
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Nov 20, 2011
I am developing a tool to get all elements of a web page (images, links etc...) and I am having a small problem with the Download button. I click it, and becuase we use a proxy at school no matter what I try it will always throw the error: "The remote server returned an error - (407) Proxy Authentification Required"How do I detect that the user is using a proxyAnd then if so, authenticate with it so that I can download the file?
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Mar 12, 2009
Processing an XML file with LINQ to add records into a table in a SQL Server database via a data context. As we are adding records we need to assign the parents in various other tables. Most of the time we can find the existing parent and use it but sometimes we will need to create a new parent.Thought we could do this like this:
Dim defaultPub As publication
defaultPub = New publication With {.name = e..Value}
Dim pub = _Data.publications.Where(Function(s) s.name =
[code].....
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Jan 4, 2012
How can I use Linq to SQL in Vb.net to combine the records of two tables into a datagrid such as shown in this example:Assume i have two tables tbl1 and tbl2
tbl1:
col1 col2
A1 B1
A2 B2
tbl2:
[Code]...
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Jun 10, 2010
I am using process.start to start Excel.The filename argument has blank spaces in the path and the argument is truncated at the first space.The error that is returned says the file cannot be found.
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