The documentation has an example about grouping on multiple properties[code]...
Is it possible to rewrite the original query to just return IEnumerable(Of CustomerRegionGroup), or do I have to use the anonymous type, and run a second query on the result of the first?
I was toying around with some of the linq samples that come with LINQPad. In the "C# 3.0 in a Nutshell" folder, under Chater 9 - Grouping, there is a sample query called "Grouping by Multiple Keys". It contains the following query:
from n in new[] { "Tom", "Dick", "Harry", "Mary", "Jay" }.AsQueryable()
group n by new
{
[Code].....
Every LINQ example I have seen for VB.NET anonymous types claims I can do something like this:
[code]...
Now when I go to iterate through the collection(see example below), I get an error that says "Name "x" is not declared. For Each x in Infos It's like VB.NET doesn't understand that Infos is a collection of anonymous types created by LINQ and wants me to declare "x" as some type. (Wouldn't this defeat the purpose of an anonymous type?) I have added the references to System.Data.Linq and System.Data.DataSetExtensions to my project. Here is what I am importing with the class:
[code]...
I have a problem using linq and anonymous types in an asp.net vb.net application.When I write the code above, I have 2 errors :
- "declarations of variable with Option Strinct On requires an As clause"
- "the name 'item' is not declared"
Public Sub MyFunc(ByVal xe As System.Xml.Linq.XElement)
Dim lstitems = From it In xe.Elements Select txt = it.@Text, value = it.@Value
For Each item In lstitems
Dim s As String = item.txt
Next
End Sub
Does it mean that is not possible to use Option Strict On and Option Explicit On ?Or I make a syntax error ?Or is it just a bad configuration of my application ?
I would like to use reflection on an anonymous type resulting from a LINQ to SQL query. I know that reflection on anonymous types works in general. The following code successfully generates a propertyinfo array with two elements:
Dim MyObject = New With {.Col1 = 1, .Col2 = "Test"}
Dim t As Type = MyObject.GetType()
Dim pilist As PropertyInfo() = t.GetProperties
[Code].....
I'm trying to write a linq to object query in vb.net, here is the c# version of what I'm trying to achieve (I'm running this in linqpad):
void Main()
{
var items = GetArray(
[code].....
I am stumped. I have a DTO object with duplicates patient address data. I need to get only the unique addresses.
[Code]...
Supposing the referenced List below contains 2 elements:
Dim Countries = From c In List _
Select New With { .Country = c.Country, .CountryID = c.CountryID }
The code above returns
.Country=Spain .CountryID = 1
.Country=Spain .CountryID = 1
How can I get the distinct values? The Countries query should contain only
.Country=Spain .CountryID = 1
Any best approach to what I'm trying to achieve (linq to sql, returning list of data to show in a grid/list etc etc)... Its complaining about anonymous type conversion, and from what I'm reading, thats not elegant way of doing it.
Public Function GetHistory(ByVal historyId As Integer) As List(Of ?????????)
Using dc As New myDataContext(Application.GetConnection)
Return (From t In dc.ActionTypes, a In t.MyTable Where a.HistoryID = historyId Select a.ActionOn, a.ActionBy, t.Description, a.ImpactedItem, a.ActionDescription).ToList
End Using
End Function
I am in the process of learning LINQ to Objects. I am querying an array of reference elements using LINQ. In the code below, which I have marked with asteriks and PROBLEM, I am having difficulty returning any values for and I suspect its because of the multiple Select arguments.
'Program name:Querying an Array of Invoice Objects
'Created/revised:
'Project description:To demonstrate the use of LINQ to query objects
[Code].....
I've got the below, where I'm grouping a collection by a propery, then wanting to access the properties of my group. Problem I have is with the anonymous typing. Because of option strict I have to give an explicit type but I can't work out what the type should be. The below doesn't compile because t.HeadAccountKey isn't a value (as t has a type of object). So either I need do some casting or my linq selector is wrong,
[Code]....
I'm trying to translate some C# LINQ code into VB.NET and am stuck on how to declare an anonymous type in VB.NET.[code]How do you translate C#'s new { ... } syntax into VB.NET?
View 2 RepliesI 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].....
Are anonymous types slower than declarative types?
For example, does
Dim score as Double = CalculateScore()
run slower than
Dim score = CalculateScore()
Why use explicit typing if it's no slower?
Assuming Anonymous Types are tailored to be used with LINQ, I'd like to use them for simply and fast data aggregation without an explicit class definition, like in this snippet[code]....
View 2 RepliesI have a Page class and a PageCollection class in a 3d party ORM framework. I can fill the PageCollection based on parameters (pageid, parentid, url etc..) (SQL query). But I need the data multiple times around the ASP.NET MVC website (Sitemap, Authentication), so I chose to load all pages 1 time and reference that (global) collection.
GlobalClass.Pages //is PageCollection containing all pages
I have now created functions which return a temporary subcollection or single entity based on the parameters mentioned before (pageid, parentid, url etc..).
GlobalClass.Pages.GetByPageId(id) //returns single page entity
GlobalClass.Pages.GetByParentId(parentid) //returns subcollection
The site however got very slow.
cache the subcollections (GetByParent())? create internal hash-lookup tables for the collection? Something else...?
Namespace BLL
Public Class PageCollection
Inherits CustomCollectionBase
[Code]....
Instinctively, I would say that this is impossible, as NHibernate needs to know some mapping information on how to persist a given type. Thus, I encountered some situations in which I could use such a feature. For instance, through a named query or something like so. On the other hand, using a named query would require me to make an addition to the configuration file.
Let's suppose we have an application interacting with some underlying datastore. This datastore is configured through the NHibernate configuration file. Then, I wish to have NHibernate load only a subset of an entity properties, from another subsystem to which my application shouldn't need to interact much, so it is not worthy to define classes for this system, as I only need a fraction of this alien system's information, let's say three out of thirty-two data columns. For that matter, if I chose to load only those three columns let's say for performance concerns, I would then use an anonymous type, perform the required action onto this information, then persist it back to the datastore. Now, it wouldn't be of much interest to do so if I only had one entity to get loaded from the datastore, so let's say I have about 75,000 rows to load into my process. I then shall consider this subset option very seriously!
What strategy should you choose in such situation, if you needed to persist these changes to a subset only of this entity's properties?FYI: I am asking because I must write specific rules of usage with NHibernate, such rules that even a beginner developer would even be able to use it without knowing too much about NHibernate, but only following the rules and guidance of the technical documents I have to produce.
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 to declare Anonymous types. I want to do a different query based on a condition.
Something like this:
If true then
Dim Myquery = From data In MyXML.Root.<hist> _
Select New With { _
.SensorID = CType(data.<sensor>(0), Integer)}
else
[CODE]...
Then I want to reference MyQuery outside of the condition. But how do I declare MyQuery outside of the if statement?
I'm trying to create a web site that users can log into and self serve their user information ie name, address etc. I've set up a SQL server DB with a couple of table holding the data and accessing those using Linq. I'm selecting specific data from my datacontext then trying to assign it to a label, ideally I want to assign the value to a class attribute so I can use the users details on multiple pages.
I've simplified the code (removing WHERE statement etc for the purposes of this question):
Using CurrentUserDataContext
As
New UserDataDataContext()
[Code].....
I'm OK with both C# and VB.NET..I have a function GetListOfBook, that returns LINQ to SQL result that has a collection of objects like the following:[code]
View 4 RepliesI'm a Linq noobie, maybe someone can point me in the right direction. What's wrong here? These anonymous types seem to have the same signatures.
[Code]...
Given two tables, customer and orders, how would one do a linq query to entities to find any customers with open invoices started before a certain date?
View 1 RepliesThis code works if I take out
" " + p.MIDDLE_NAME
Thus the remaining code looks like:
p.FIRST_NAME + " " + p.LAST_NAME
Maybe LINQ-to-Entities just doesn't support concatenating more than two strings at a time?
Protected Sub btnFilter_Click(sender As Object, e As EventArgs) Handles btnFilter.Click
Dim dbContext As Campus6Entities = New Campus6Entities
[Code]....
I have seen other similar questions dealing with WPF Almost exactly the same but I can;tfigure this out in ASP.net. I have a Pages table with a parentpage foreign key and want to databind them to a treeview. In the past I have created a hierarchicaldataset from a dataset but would like to stay within the entities framework if I can
View 1 Repliesthe query below throws a System.NotSupportedException: "Unable to cast the type 'System.Linq.IOrderedQueryable1' to type 'System.Linq.IQueryable1'. LINQ to Entities only supports casting Entity Data Model primitive types." The exception is only raised in the VB.Net version. When translated to C#, no exception is raised.
Dim doesThisCrash = From outerOrder In orders
Where outerOrder.ProductId =
(From p In products Join o In orders On p.Id Equals o.ProductId
[Code]....
I am using LINQ with Entity Framework, and I need to get the SQL server timeCan anyone tell me how can I create a method so it retrieves the current server time?
View 1 RepliesI'm a bit of a n0ob to all this and I'm having trouble finding good resources on the net.What I'm trying to do is define a one-to-many relationship between two entities. I'm using the GUI tool in Visual Studio - and have created the tables in Microsoft SQL Server Management Studio.Basically, I have two tables....a 'Users' table and a 'Sites' table. A single user can have many sites associated with it.Users has a primary key of 'UID' and the Sites table as a primary key of 'Site_ID'.Sites also has a column 'UID' that should indicate which user that site is associated with.Anyway - it sounded pretty simple; but no matter what I attempt to do, I can't seem to get it to work. Mostly, I get validation errors - sometimes run-time errors, or sometimes, no actual data even though there should sites that match the UID of the user.I am able to connect and write LINQ against my Users table/pull down User objects - but can't seem to get it to know that the Sites are associated with the user.In the GUI - if I go to 'Add Association' and create a 1 to many link between Accounts and Sites - and Validate - I get an error saying, "Error1Error 11008: Association 'AccountsSites' is not mapped."
It seems like, when I try to make an association, it wants to link the 'Keys' of each entity.But U_ID and SITE_ID are the keys and, obviously, shouldn't match.If I click on the line it created in the GUI and I go to 'Table Mapping' I can see that it is trying to match those keys. Since I want it to match user_ids my first thought is to just make the U_ID the entity Key in the Sites entity but, of course, that's wrong because it would no longer allow a 1 to many relationship.
Basically I have the follwing:Dim ctx As New AdminCoreEntities Dim roles = (From r In ctx.Roles where r.Name.StartsWith("cust") Select r) 'list of System .Linq.IQueryable(Of AdminCoreModel.Role)
[code]...
The error i get when i run this is: Unable to cast object of type System.Data.Objects.ObjectQuery`1[AdminCoreModel.Role] to type AdminCoreModel.Role
Basically I have a many to many situation and I try to get all the Quicklinks objects queried by their roles and not quite sure why EF will cast to a single AdminCoreModel.Role when i.Roles is a collections of objects.
I am trying to write a query for an existing database, I am using LINQ on EF3.5 inside VS2008 as that is the only environment available to me.I have a starter query that gives me a list of items so the user can select what they want.
"e.Result =
From c In MLDb.TBL_FeatureInfoSet
Order By c.INSP_ROUTINE_NM
Select c.INSP_ROUTINE_NM
Distinct"
The user can then select from the list one or several items they are intersted in and i want to use these as the filter in a further database call. It's not then difficult to have a where to filter on one string however, I would also like to be able to allow the user to select several items from the list box and the data for all of those to be returned.
[Code]...