.net - String Where In LINQ To Objects
Jun 5, 2012
I have a linq query like that:
Elementos = From b In Elementos Where b.Value.IdGrupo = 0 Select b
"Elementos" is a dictionary(of long, MyObject). MyObject has approximately 50 properties.
The problem I have is that I have a new requirement to accept string parameter with a "where" condition. Something like "property1>10 and property2 like 'anystring' or property3<=25". (That means any property could have a condition. I have string and numeric properties.)
I'd like to keep using linq, adding the condition as it comes. I'm aware that it could produce an exception if the condition is misspelled or something, but that's acceptable (by try catchs). I wouldn't want to parse the string to build parameters or anything.
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Apr 27, 2012
I figure I should use 'Aggregate' but apparently I am getting it wrong First I get a list of my Entity objects Dim employers As List(Of myEntity) = (New XXXX()).getZZZ(userName, userType) Then I figured this would be a way to put all the names in a string Dim names as String = employers.Aggregate(Function(current, [next]) current.Name & " " & [next].Name)
[Code]....
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Jan 18, 2012
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Using conn As New SqlConnection("Database=Clinic_Management_System;Data Source=.SQLExpress;Integrated Security=True;AttachDBFilename=|DataDirectory|Clinic Management System.mdf")
Dim cmdRecord As SqlCommand
[code]....
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Feb 21, 2009
In which situations I should use LINQ to Objects?
Obviously I can do everything without LINQ. So in which operations LINQ to code shorter and/or more readable?
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Nov 20, 2009
I am creating a tool that interfaces with an API for a CD/DVD burner. I have created several custom classes that will hold the information for the disk sets (which consist of a data path and a label file among other information. The DiskSet class has a list of Include objects. My proposed XML output would be something similar to the following:
<DiskSets>
<DiskSet>
<Name>MySet 1</Name>
[code].....
I am attempting to traverse the Includes collection (I have tried List and Binding List as I am also using this in a pair of datagridview controls) and it keeps returning Expression of type 'Object is not queryable. Make sure you are not missing an assembly reference and/or namespace import for the LINQ provider." How can I use LINQ to pull a list of the Include objects under each DiskSet object for transformation into XML? I am hoping to keep this restricted to this one block of code if possible.
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Apr 14, 2010
Using the following code:
Private Sub MakeMeSomeXmlBeforeRyanGetsAngry()
Dim db As New MyDBDataContext
Dim customer = From c In db.Customers Select c
[code]....
I am attempting to serialize my linq collection of customers. But it keeps throwing
Type 'System.Data.Linq.DataQuery`1[MyDB.Customer]' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. See the Microsoft .NET Framework documentation for other supported types. My issue is that I have already marked the dbml Serialization Mode to UniDirectional and when I check the dbml codebehind all of the DataContract()> and DataMember()> elements are there. I have tried adding various dataloadoptions and setting deferredloading to false, but no luck.
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Dec 15, 2011
How to Join the objects in a LINQ select in this sample (C# variants accepted as well):
Class Room
Public Area As Integer
End Class
Class RoomPair
[code]....
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Mar 10, 2010
Im trying to use LINQ to query Objets. I'm doing the following:
Dim myList As Generic.List(Of MyItem) = (From ThisItem In LinqToSqlObject.Items _
Join Folder In LinqToSqlObject.Folders _
On Folder.Id Equals Item.Id _
[Code]....
This however will not return any item that has a ParentItemId of null. I am trying to do a left join so as to return all "Item" regardless of whether it has a parent or not. I am aware that this is feasible in C# by adding an "into X" on the join, and selecting from X.DefaultIfEmpty(), this however does not appear to work in VB.Net.
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Mar 1, 2011
I have list object and I need to check id in a comma separated string using LINQ in VB.NET, something like this:
dim strId as String = "1,2,3,5,"
dim myList = from objmylist where objmylist.id in (strId)
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Dec 10, 2010
I have the following XML file
<Test>
<Modules>
<Module Name= "Test1">
<QueueName Name="Test1Active1" Active="True"></QueueName>
<QueueName Name="Test1Active2" Active="True"></QueueName>
[Code]...
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Oct 2, 2010
I'm trying to figure out how to add an enumeration to an object with Linq. For example:
Dim thingBlock = <Things>
<Thing Name="Ish">
<SmallThing>Jibber</SmallThing>
[code].....
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Apr 5, 2011
I'm trying to create a list of all my objects from several lists of objects using Union.
Return Chart.AnnotativeNodes.Union( _
Chart.DecisionNodes.Union( _
Chart.EndNodes.Union( _
Chart.StartNodes.Union(Chart.WorkCenterNodes))))
The above line gets an error because I can't union List(of AnnotativeNode) with List(of DecisionNode). Each list defined like List(of EndNode) or List(of StartNode), but each class inherits from the base type Node.Is there a possible way to union these to get a result of IEnumerable(of Node)?
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Feb 25, 2009
This feels like a completely basic question, but, for the life of me, I can't seem to work out an elegant solution.
Basically, I am doing a LINQ query creating a new object from the query. In the new object, I want to generate a auto-incremented number to allow me to keep a selection order for later use (named Iter in my example).
Here is my current solution that does what I need:
Dim query2 = From x As DictionaryEntry In MasterCalendarInstance _
Order By x.Key _
Select New With {.CalendarId = x.Key, .Iter = 0}
[Code]....
Is there a way to do this within the context of the LINQ query (so that I don't have to loop the collection after the query)?
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May 27, 2011
I have an object that looks like follows:
Public Class MyObject
Public Property Key as Intger
get 'Elided for clarity
[code].....
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Feb 1, 2011
Is there any way to use a LINQ to XML to query an XML document like the one below to create new (anonymous or strongly typed) objects from the child elements of a descendant? Here is my XML document:
[Code]...
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Mar 15, 2012
I have collections of 2 different types - let's call them Cars and Trucks. Both share base class Vehicle, which has property Passengers.I want to merge them into a single collection ordered by that property. E.g., merge Cars and Trucks and order by Passengers.
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Oct 13, 2011
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.
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Sep 15, 2011
I need to query an array. I have tried to use LINQ but with no success.
Here is a simplified structure of Insurance
Public Class Insurance
Public _typ As String
Public _numb As Number()
[Code]....
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Oct 11, 2011
I have a list of objects, each with 2 relevant properties: "ID" and "Name". Lets call the list "lstOutcomes".I need to check the list for duplicates (meaning object1.ID = object2.ID, etc.) and set a flag (valid = false, or something) if there is at least one duplicate. Also, it would be nice to send a message to the user mentioning the "Name" of the object, when it fails.I am sure I will need to use the Group By operator to do this, but I am not used to doing that in LINQ, and the examples out there are just not helping me. This article seems to be close to what i need, but not quite and it's in C#.
Here is a starting stab at it...
Dim duplist = _
(From o As objectType In lstOutcomes _
[code]......
help?
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Oct 25, 2011
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].....
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Sep 28, 2010
How do I order by and group by in a Linq query?I tried..Dim iPerson = From lqPersons In objPersons Where Len(lqPersons.Person) > 0 Group lqPersons By key = lqPersons.Name Into Group Order By Group descending Select Group, key
For Each i In iPerson
tmp = tmp & vbNewLine & i.key & ", " & i.Group.Count
Next
[code].....
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Sep 19, 2009
I am having a little problem with some homework. Here is the problem:Use the Invoice Class provided to create an array of Invoice Objects. Class Invoice includes four properties- a PartNumber (type integer), a PartDescription (type String), a Quantity of the item being purchased (type Integer), and a Price (type Decimal). Write a Console Application that performs the following queries on the array of Invoice objects and displays the results:
[Code]...
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May 3, 2012
I have a query that 'selects' object of a type:
Dim l as IList(Of Foo) = (From dataRow As DataRow In table.Select()
Where CStr(dataRow("Column1")) = "A"
Select New Foo(CStr(dataRow("Column1")), _
CStr(dataRow("Column2")))).ToList()
What's happening is that if i set a break-point to the constructor of Foo and step, the constructor is hit and the parameters are loaded with the arguments. However, l has empty Foo objects (the members in every object are Nothing). What could be happening here?
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Jul 7, 2011
I have
Dim objectsList as List(Of Object) = GetAllObjects()
' Filter from Objects just Persons '
Dim peopleList as List(Of Person) = ???
What is the most efficient and effective LINQ expression to do it?
EDIT
1 Dim selectedObjects As List(Of Object) = GetAllObjects()
2 Dim selectedPeople As IEnumerable(Of Person)= selectedObjects.OfType(Of Person)
3 Dim people As List(Of Person) = selectedPeople.ToList()
Error on 3:
Value of type
'System.Collections.Generic.List(Of
System.Collections.Generic.IEnumerable(Of Person))' cannot be
converted to
'System.Collections.Generic.List(Of Person)'.
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Nov 16, 2010
I am having trouble following some of the examples at MSDN for LINQ.Basically I have a List Of MyObject. MyObject has a property called Value which is an integer.I want to group all the MyObjects together that share the same Value and then return that Value where the count of the group is greater than 5.I have tried the following,
dim foak = From o as MyObject in MyObjectList _
Group o By o.Value into Count _
WHERE Count > 5 _
Select o.Value
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Feb 3, 2010
Basically, I am trying to write a LINQ to Objects statement where the relationship is a grandparent, parent, child relationship. (You could also call it a Master Detail relationship.)
In Legacy code here is a simplified version what I am trying to accomplish.
Dim coverages As New List(Of Coverage)
Dim coverage As Coverage
For Each rl In oClaimsPolicy.RiskLocations
coverage = New Coverage
coverage.Level = "Location"
[Code] .....
If is it not clear one Location can have many Items and one Item can have many Coverages. I basically want to list the items and show the relationship between grandparent (Location), parent (Item) and child (Coverage).
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Jul 3, 2011
I am having so trouble with the ToUpper() procedure with strings. I am using LINQ to find unique values in a list of objects. In that whole process I set the values to compare to all lowercase in order to get a proper list. My goal is to populate a dropdown list with the values. I'm attempting to set the first letter of of the string to uppercase and keep the rest lowercase however the toUpper() procedure is not working?
Private Function FixCase(ByVal strIn) As String
Dim strOutput As String
Dim intStringLength As Integer = strIn.Length - 1
strOutput = strIn.Substring(0, 1)
[code].....
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Sep 20, 2009
Use the Invoice Class provided to create an array of Invoice Objects. Class Invoice includes four properties- a PartNumber (type integer), a PartDescription (type String), a Quantity of the item being purchased (type Integer), and a Price (type Decimal). Write a Console Application that performs the following queries on the array of Invoice objects and displays the results:
a. Use LINQ to sort the Invoice Objects by PartNumber
b. Use LINQ to sort the Invoice objects by Price
c. Use LINQ to select the PartDescription and Quantity and sort the results by Quantity
d. Use LINQ to select from each Invoice the PartDescrition and the value of the Invoice (i.e. Quantity * Price). Name the calculated column InvoiceTotal. Order the results by InvoiceTotal.
e. Using the results of the LINQ query in Pard d, select the InvoiceTotals in the range of $200 to $500
I am pretty sure I have parts a, b, & c completed correctly. Or at least the provide the desired results. Part d I figured out how to multiply the 2 fields but can't create a new column for the result or figure out how to show the PartDescription with the multiplied result. Part c I think I can figure out when I get part d. I already coded what I think will work for part c.
Below are the 2 Objects the Invoice was given and not to be changed & the LINQ is the one I have been working on.
Module LINQ
Sub Main()
' array of invoices
Dim invoices As Invoice() = { _
New Invoice("83", "Electric Sander", "7", 59.98), _
[Code] .....
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Aug 31, 2011
I don't know if this is doable, maybe with Linq, but I have a List(Of MyType):
Public Class MyType
Property key As Char
Property description As String
End Class
And I want to create a Dictionary(Of Char, MyType) using the key field as the dictionary keys and the values in the List as the dictionary values, with something like:
New Dictionary(Of Char, MyType)(??)
Even if this is doable, internally it will loop through all the List items, I guess?
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Mar 24, 2011
I am creating a mediaplayer / playlist creator tool that basically imports MP3 songs into playlists (grids). I'm looking to add search functionality where the user can search all open playlists (or a subset of the open playlists). A Playlist is basically a collection of AudioFiles, where an AudioFile is a class that holds the filename of the MP3 file and then exposes the tags (Title, Artist, Album, etc) in public properties.
The idea is that the user can search for a certain expression (for example "the"), and that he can then choose whether to search in the title, in the title and artist, in the title or artist, in the title, artist and/or album, etc. However, I'm having a hard time implementing this and also having it kind of dynamic.
At the moment I am simply gathering all the AudioFiles from the open playlists (or from the subset of playlists the user chooses) and then running a simple LINQ query to find those AudioFiles where the Title contains the search text. Then I display the resulting AudioFiles in a new playlist window:
[Code]....
In case the AND / OR distinguishing is too hard, I would be happy to start with just letting it default to 'OR', so that the user can check Title and Album for example. If he would then search for 'a' then all songs that contain 'a' in their title as well as all songs that contain 'a' in their album should be returned. I guess that makes it easier, but I still wouldn't know how to dynamically create the LINQ query.
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