.net - AndAlso In VB Linq Query Doesn't Seem To Be Working?
Sep 14, 2010
The below query fails with Null Reference Exception when there are elements in BOMIDs where MatID property is nothing.I thought the 'x.MatID isnot Nothing AndAlso' would prevent the x.MatID.Process part of the where from being executed. There are a couple elements in the BOMIDs collection that where MatID is nothing.
From x In BOMIDs _
Group Join y As PurchasedProcess In SpecialProcesses _
On x.MatID.PurchasedProcess Equals y.Name _
Into G = Group _
I have used persistance class and used following LINQ query.[code]but it throws an error saying. "Specified Method is not Supported".How can i get data from two table using XPO Persistance Class?
I know that LINQ queries are deferred and only executed when the query is enumerated, but I'm having trouble figuring out exactly when that happens.Certainly in a For Each loop, the query would be enumerated.What's the rule of thumb to follow? I don't want to accidentally enumerate over my query twice if it's a huge result.
For example, does System.Linq.Enumerable.First enumerate over the whole query? I ask for performance reasons. I want to pass a LINQ result set to an ASP.NET MVC view, and I also want to pass the First element separately. Enumerating over the results twice would be painful.It would be great to turn on some kind of flag that alerts me each time a LINQ query is enumerated. That way I could catch scenarios when I accidentally enumerate twice.
I use Visual Studio 2003, VB.net, NetFramework 1.4 and Windows XP I have been using the following Code Snippet for a number of years in both Web Services and Windows Applications. However suddenly around the 29th September 2010 it has stopped sending E-Mails from both Web Services and Windows Applications. The same problem has happened not only to my own Network but on two other Networks, one using XP as its Server and the other using Server 2003. All 3 of these are using different ISPs.
I have to join two main tables, and I need to filter the results by elements in an ASP.NET web form. These filters are created on the fly so I have to use a lot of where extensions to filter the query. I want to execute the query with as optimized SQL as possible.
I am first doing a simple join between TW_Sites and TW_Investigators. Then there are two sub-tables that are involved. TW_InvestigatorToArea and TW_InvestigatorToDisease. While most of the where clauses are working fine, I have found a performance issue that won't be an issue right now, but will be an issue as the table gets bigger.
The arrays DiseaseCategories and DiseaseAreas would be the results of a CheckBoxList result.
Protected Sub LoadResults() 'Get Dictionary of Filters Dim FilterDictionary As OrderedDictionary = Session.Item("InvestigatorFilterDictionary") ' Initialize LinqToSql
Forgive my ignorance on this.I have this LINQ Query:Dim ngBikersDataContext As New CarBikeWalkDataContext
bikersList = (From c In ngBikersDataContext.Reg_Bikers _ Order By c.L_Name _ Select New Bikers() With { _ .BikerID = c.BikerID, _ .F_Name = c.F_Name, _
[Code]...
with the error "Overload resolution failed because no accesible 'Select' accepts this number of arguments." Over the "NEW" I get an error " ')'expected."
We are doing a query against an in-memory collection of LINQ data objects. The wrinkle is that we are ordering by a column in a related table whose records have not necessarily been loaded yet (deferred loading:)
Dim oPkgProducts = _ From b In oBillPkg.BillProducts _ Where b.Successful.GetValueOrDefault(Common.X_INDETERMINATE) = _
How do I add ROW_NUMBER to a LINQ query or Entity? How can I convert this solution to VB.NET?
[Code]...
I'm having trouble porting that last line. I have been unable to locate a VB.NET example. I'm actually not looking for any paging functionality like the example provides, just good old-fashioned Row_Number(Order By X) row index.
I just upgraded a project from VB 2008 to VB 2010. Before, the project did not use LINQ. I have started implementing it. So, I have updated the target framework from 2.0 to 3.5, and added a reference to System.Core, and imported the namespace System.LINQ to the entire project and also imported System.Data.LINQ into the form I'm working with (because it was not available in the list for Imported Namespaces in the references tab).
It's not throwing any errors now, but my IntelliSense is not working for LINQ stuff.
For example... I write this:
[CODE]....................
Then, if I type S. on the next line, the IntelliSense doesn't grab what it should for S (Only get Equals, GetHashCode, GetType, ReferenceEquals, and ToString, instead of the options I should get like Count, First, FirstOrDefault, etc...). If I Type S.First. then its the same thing, no IntelliSense that lists the available fields for S, just the standard options (Equals, GetHashCode, GetType, ReferenceEquals, and ToString). I should be seeing my column names in my table when I type S.FirstOrDefault.
So any ideas what is going on? When I type the code, for example, MessageBox.Show(S.FirstOrDefault.FirstName), it works perfectly. But it doesn't change the casing of the text (so it would read s.firstordefault.firstname) and no intellisense while doing it. But no errors. BTW - Everything works perfectly when creating a NEW VS 2010 application, it's just my projects upgraded from Visual Basic 2008 that have this issue.
I was wandering is it possible to use a query within another query below is the code I am trying to use.
Public Function GetInventByComp(ByVal CompID As String) Using DC As New DataClassDataContext 'need to get company id's based off names? thats bad should be name from Id need to rethink this Dim invent = (From C In DC.Inventors_Companies _ Where C.CompID = CompID _ Select C.InventorID).ToString
[Code]...
I was trying to us multiple values in a string like "1, 3, 5" but I can't seem to get that working either so I am trying to use just a single value now. Can anyone help me? "Yes I am new to this"
My module won't run, it can't find the project or library, and highlights: the Date function in: MsgBox (Date).This is happening to several VBA functions, but this is the first one.I have all the libraries referenced that I think I need, especially the Visual Basic for Applications checked.There is a MISSING: Office12 library, but the Date function is part of the VBA library, so I don't think this should be the issue.
When writing an If statement, I've always used And when needed like: If 1=1 And 2=2 Then. The only time I ever used AndAlso is if the second condition will error if the first isnt true like: If Not IsDbNull(Value) AndAlso Value=2 Then. However, recently I've heard that AndAlso is better for performance than And as the second condition is only read when the first is true. In this case, should I always just use AndAlso?
I am developing a Winform Program in visual basic and I am using Access Tables. I want to use a bindingsource filter to do a search on Stock descriptions. I am using this but it doesn't seem to be working
Me.StockBindingSource.Filter = "ITEMNAME LIKE '%" & SearchTextBox.Text & "%' AND [Supplier1 Price] <> 0 AND [Supplier2 Price] <> 0 AND [Supplier3 Price] <> 0"
What's happening is that I am only seeing products where all 3 suppliers have a price listed that isn't 0. (Products have a zero price when it becomes discontinued or supplier doesn't sell that product but we may have purchasing history against it so it can't be deleted). Therefore we do end up with products where all 3 suppliers have a zero cost. These are the products I don't want this search to return.
I have built a Wpf-ControLibrary-Project to put some Controls there. In one Control i need to get some informations about assambly, Version and directory path.in the past i have done this one:
What is the difference between (OrElse and Or) and (AndAlso and And)?Is there any difference in their performances, let say the correctness benefit?? Is there any situation that I shoudn't use OrElse and AndAlso?
Im trying to check service on a remote server.. as i was typing this i kept getting a syntax error on AndAlso statement.
Also, how do i add the path to connect to a remote server to check the service?
Private Sub CheckServiceButton_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckServiceButton.Click ' This will check if the service is running '
I am trying to read data from remote SQL base. I have written the function that works great if you need to get 1 Value , but when I want to read 2 or more value at from one query it doesn't work [Code]
I'm very new to VB, so I was in the very first tutorial, it has me play a sound file. So I put that in, ran it, and it came back with an error saying "system cannot find this file." I guess I'm not terribly surprised, since the file they gave has no C: or anything like that. What I want to do now is play my very own sound file, but I don't want to go through the whole C:Documents and Settings... thing, so is there a way I can put my own sound file in the project directory and say something like %ProjectDir%/sounds/mysound.wav?
Looking at the following code snippet in VS2008 (this is from the SBS book)
Dim HumanAge As Integer = 0 If HumanAge <> 0 And 7 / HumanAge <= 1 Then MsgBox("1 dog year or older")[code]....
I expect to get a runtime error, because And evaluates both conditions, which is why in this case AndAlso should be the better operator to use. When I try this code there is no difference in behavior between 'And' & 'AndAlso'. In neither case I get a runtime error, not even when I flip the conditions around. Is this by design, a lucky accident, or do I just not get it?
