I recently switched from VB to C# and have, for the most part, been able to make the transition without too much trouble. Currently I am working on converting a VB.Net program into C# and am having trouble with a couple of code blocks that include Linq.
This is one of the VB.Net lines of code that I am having trouble with:
I have tried to do the same thing in C# like this:
I am getting a compile error on the dt, which says Could not find an implementation of the query pattern for source type 'System.Data.DataTable'.'GroupBy' not found. VS also has issues with the whole into Emailers = group;
I have tried to get this right using examples from my search but have not been able to get it right.
I'm in the process of teaching myself C# by converting an existing project and am stuck converting the following vb linq code:
Dim outStuff = From tt In (From t In Products.SelectMany(Function(p) If(p.tags IsNot Nothing, p.tags, New ObservableCollection(Of TagModel))) Group By tagName = t.name, v = (Aggregate p In Products Where If(p.tags IsNot Nothing, p.tags.Contains(t), Nothing) Into Sum(p.views)), nl = (Aggregate p In Products Where If(p.tags IsNot Nothing, p.tags.Contains(t), Nothing) Into Sum(p.num_likes))
[Code]...
var x = Products.SelectMany(p => (p.tags != null) ? p.tags : new ObservableCollection<TagModel>()); var tags = from t in x group t by t.name into g select new { tagname=g.First().name};
I need help converting datatable to xml using Linq. I could do it with hardcoded column names as you can see in my code .. but i need it without hardcoding it ..Example datatable ..My linq query ..
Dim xmlDoc As New XDocument( From row In dt.AsEnumerable() From row In dt.AsEnumerable()[code]......
I'm having a little trouble converting some LINQ to VB.[code]Online code translators are not helping, and my unfamiliarly with VB LINQ is not very good.
I have a function that works great in C# that I'm converting to VB.Net. I'm having an issue converting the result set to a generic list in VB.net.
The code:
Public Function GetCategories() As List(Of Category) Dim xmlDoc As XDocument = XDocument.Load("http://my_xml_api_url.com") Dim categories = (From category In xmlDoc.Descendants("Table") _ Select New Category()).ToList(Of Category)() Return categories End Function
The error occurs when convertng the result via .ToList(Of Category)() The error:
Public Function ToList() As System.Collections.Generic.List(Of TSource)' defined in 'System.Linq.Enumerable' is not generic (or has no free type parameters) and so cannot have type arguments.
Category is a simple object I've created, stored in the App_Code directory.
I have the necessary "Imports System.Collections.Generic" reference in the file so I don't see why I can't convert the result set to a generic list.
I am trying to get the DataView from a linq query expression which is querying a typed dataset. The result lands in a type of System.linq.IOrderedEnumerable. But i'm not able to convert this type to a Dataview although a few examples on the internet say that AsDataView function shoudl work but could you please throw some light on why the method AsDataView is not exposed on the query.
I'm having trouble getting my head around converting a traditional SQL aggregate query into a LINQ one. The basic data dump works like so:
Dim result = (From i As Models.InvoiceDetail In Data.InvoiceDetails.GetAll Join ih As Models.InvoiceHeader In Data.InvoiceHeaders.GetAll On i.InvoiceHeaderID Equals ih.ID
[CODE].....................
What I need to really be getting out is ih.Period (a value from 1 to 12) and a corresponding aggregate value for i.ExtendedValue. When I try to Group ih I get errors about i being out of scope/context.
I'm using Linq to Sql and have a stored proc that won't generate a class. The stored proc draws data from multiple tables into a flat file resultset. The amount of data returned must be as small as possible, the number of round trips to the Sql Server need to be limited, and the amount of server-side processing must be limited as this is for an ASP.NET MVC project. So, I'm trying to write a Linq to Sql Query however am struggling to both replicate and limit the data returned. Here's the stored proc that I'm trying to convert:
I have a listbox on my xaml form that I bound to a List(Of MyType) property. I populated this list like so:
Dim fields As List(Of CheckableFields) = New List(Of CheckableFields) Using context As ITIPEntities = New ITIPEntities() Try[code]....
Now I'm at the point where the user selects the fields they want included in a report and I need to iterate over the required fields. This is my linq query:
For Each checkedField In _requiredFields If checkedField.IsChecked Then If checkedField.FieldData IsNot Nothing AndAlso checkedField.FieldData.Trim IsNot String.Empty Then[code].....
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) = _
The pattern I'm trying to avoid is checking if a string (normally a control's text value) is null/empty, and if it is, comparing it using Contains to a field in my data. Obviously the field isn't hard-coded into my extension, neither is the object type.What I've got works perfectly in Linq to Objects, but I get the generic run-time error "LINQ to Entities does not recognize the method 'System.String Invoke(GenericQueryHelper.Customer)' method, and this method cannot be translated into a store expression." when using an entity framework model.
Here's what I have:
<System.Runtime.CompilerServices.Extension()> Public Function CompareAndFilter(Of T)(source As System.Linq.IQueryable(Of T), expressionField As System.Linq.Expressions.Expression(Of System.Func(Of T, String)), compareTo As String)
[code]....
I want my usage to look something like this:
Dim results = repository.Customers.CompareAndFilter(Function(c) c.FirstName, searchText)
I do need to get this running against a SQL database really, as it is filtering results, so I don't want to be doing that in memory.
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.
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
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 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.
suppose I wanted to make a function that returned a list of people based on 2 criteria ... FirstName = 'Ed' Or LastName = 'Smith'.The key here being the OR. If I do something like the following:
dim qry = From p in db.Person select p.FirstName, p.LastName qry = qry.Where(Function(p) p.FirstName = 'Ed') qry = qry.Where(Function(p) p.LastName = 'Smith')
I am having some difficulties with sending XML data to SQL using Linq.I have been following the tutorial link below, however my XML data doesn't contain a root value like <order number> to go through each of the XML data. There is no unique reference as part of the <quote> information.[URL]..
Is there a way I can submit the changes to SQL using the <reference> field as the unique field even though it is not related to <quote>?
I'm having a heck of a time with transforming a simple SQL Query into a LINQ query(using vb btw)
Here is my SQL: SELECT USRDEFND5 FROM int_gp_employee GROUP BY USRDEFND5
[Code]...
I've tried a number of different variations of the LINQ. My current statement is:
From b In xmlFile...<row> Group b...<usrdefnd5> By b...<usrdefnd5> INTO group when I foreach through the resulting collection, EVERY line (17000) shows up.
I am using LINQ to XML to take some data from resources , and here I have a function, where I take some values and then I create a new object (Type Translation), so when I call the function I get a Translation object. By now I have this code:
Public Shared Function RetrieveTranslation(ByVal file As String) As List(Of clsTranslation) Dim valuetrans = From vl In XElement.Load(file).Elements("data") Select (New clsTranslation With {.Filename = file, .Value = vl.Element("value").Value, .TranslationId = vl.Attribute("name").Value}) Return valuetrans End Function
The problem is that with this code I got this error:
Unable to cast object of type 'WhereSelectEnumerableIterator2[System.Xml.Linq.XElement,clsTranslation]' to type 'System.Collections.Generic.List1[clsTranslation]'.
I have an XML file, with a rather large structure. I'm pulling several entities out of it throughout several systems, and its dynamically updated once a day. I'm using a Linq Query that is exhibiting odd behavior, its only returning if the first entry in the site tag matches the search-pattern. If its number 2 or 3, it fails to return anything. Why would this behave that way?
The following function written in VB handles pulling the data
Public Function xmlSchoolListBySite() As IEnumerable Dim doc As XDocument = loadXML() Dim loadedPrograms As IEnumerable(Of XElement) = From c In doc.Descendants("Organization") _ Where c.Descendants("site").Value = MySite.Site.s_Url _ 'contains Result.RawURL.tostring() formatted Select c.Element("Title")
I've been reading a fair bit about the performance of using LINQ rather than using a for each loop and from what I understand using a LINQ query would be a little bit slower but generally worth it for convenience and expressiveness. However I am a bit confused about how much slower it is if you were to use the results of the query in a for loop.
Let's say that I have a set called 'Locations' and a set of objects called 'Items'. Each 'item' can only belong to one 'location'. I want to link items that are under the same location to each other. If I were to do this using a normal 'For Each' loop it would be something like this:
For Each it as Item in Items If it.Location.equals(Me.Location) Me.LinkedItems.Add(it) End If Next
However if i was to use LINQ it would instead be this:
For Each it as Item in Items.Where(Function(i) i.Location.equals(Me.Location)) Me.LinkedItems.Add(it) Next
is the second (LINQ) option going to loop once through the entire 'Items' set to complete the query, then loop through the results to add them to the list, resulting in essentially two loops, or will it do the one loop like the first (For Each) option?
