Linq Query Dynamically Add Where Condition?

Sep 3, 2010

I want to filter records dynamically on user choice. The user may choose to show the debit amount greater than credit or credit amount greater than debit. Accordingly I want to put a condition similar to either totDebit>totCredit orTotCredit>totDebit`

Dim query = _
From product In Bills.AsEnumerable() _
Group product By accode = product.Field(Of String)("ACCODE"), _

[Code]....

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Iif Condition In Linq Query Where Clause

Aug 25, 2011

Whats wrong with the below query, I am getting this error: Nullable object must have a value.

[Code]...

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Query For Namespace Dynamically Using Linq To XML?

Mar 5, 2012

I have 290 Group Policy Backup xml files which I need to enumerate in separate folders.

With each Group Policy backup xml file, I need to query the Policy settings.

Anyone who's looked at a Group Policy xml backup file before would know they're chock-a-block full of Namespace declarations.

I want to know, using Linq to XML, as I query each xml file, how can I dynamically query the XML the Namespace and then append the Namespace into the Linq query for the child nodes/values?[code]...

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Dynamically Building LINQ Query Using OR Operator In VB

May 22, 2009

I need to build a dynamic linq query with or operators. I have seen PredicateBuilder but that is in C# and my project is in VB. Basically I need to build a WHERE clause similar to this:

Where((this = 1 AND that = 2) OR (this = 1 AND that = 4) OR (this = 2 AND that = 4))

but the problem is the number will have to be determined dynamically at runtime, and added using a loop, like

for each item in myItems
query = query.OR (this = item.a AND this = item.b)
next

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VS 2010 Dynamically Building LINQ Query To Search Objects

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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LINQ Query Is Enumerated - Turn On Some Kind Of Flag That Alerts Me Each Time A LINQ Query Is Enumerated?

Sep 22, 2009

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.

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IDE :: Aggregate Query With Condition ?

May 28, 2012

i have 1 query with aggregate with condition using access

SELECT
HD.No,
SUM(IIf(DT.Status = 'A', 1, 0)) AS One,[code]...

i can run it in access but not in .Net QueryBuilder

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LINQ -> Extra Condition On Left Join?

Aug 19, 2010

I'm basically trying to emulate a query like the below in LINQ:

DECLARE @id INT
SET @id = 1
SELECT
q.txtLQRdisplayName AS DisplayName,

[code]....

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Update Columns In Datatable Using Linq Without Condition?

Jun 22, 2011

How to update columns in datatable using linq without conditions. I have an idea that I'm just gonna loop all the data in the datatable but don't know what comes in LINQ.

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Sql Query WHERE(condition) - Date Format

Sep 8, 2009

QuoteI am facing the problem in select the item dates. This is because i only want the condition of month from table dates. So i think the data set i write it get the error.

[Code]...

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LINQ Statement Where Result Count Is Used In Expression's Condition?

Mar 23, 2009

I have a requirement where I have to add items into a List(Of T) (let's call it Target) from an IEnumerable(Of T) (let's call it Source) using Target.AddRange() in VB.NET.

Target.AddRange(Source.TakeWhie(Function(X, Index) ?))

The ? part is a tricky condition that is something like: As long as the as yet unenumerated count is not equal to what is needed to fill the list to the minimum required then randomly decide if the current item should be taken, otherwise take the item.Somethig like...

Source.Count() - Index = _minimum_required - _curr_count_of_items_taken _
OrElse GetRandomNumberBetween1And100() <= _probability_this_item_is_taken
' _minimum_required and _probability_this_item_is_taken are constants

The confounding part is that _curr_count_of_items_taken needs to be incremented each time the TakeWhile statement is satisfied. How would I go about doing that? I'm also open to a solution that uses any other LINQ methods (Aggregate, Where, etc.) instead of TakeWhile.If all else fails then I will go back to using a good old for-loop =)

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.net - ActiveRecord Linq/NHibernate Linq Not Building Query Completely?

Jul 14, 2011

given this function:

Public Function Search(ByVal StartIndex As Integer, _
ByVal MaxResults As Integer, _
ByVal AccountNumber As String, _
ByVal LastName As String, _

[Code]....

instead of what I expected:

Select count(*) from remitline where lastname = "smith"

What am I doing wrong building up the where clause? I'm using Castle ActiveRecord 2.1

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Performance Gain In LINQ Query Vs LINQ Stored Procedure?

Aug 6, 2009

if there is that much of a performance gain in running a LINQ stored procedure versus a LINQ query?

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How To Declare Anonymous Types - Different Query Based On A Condition

Jun 29, 2009

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?

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Asp.net - Complex Linq Query - Add A .Where() Or .Any() Predicate To Reduce Query Complexity (in VB)?

Sep 14, 2010

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

[code]....

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LINQ Query Using The Dynamic LINQ Library?

Mar 31, 2011

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."

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C# - Make Service Act Dynamically Based On Service Running Condition?

Jul 6, 2011

i was trying to make my service act dynamically... i have set time for my service about for 2 min ,if suppose it was doin huge amount of work means it will exceeds that 2 min time limit then we need to check the service condition if work is pending means we need to run that instance until upto finish.

public static void StartService(string serviceName, int timeoutMilliseconds)
{
ServiceController service = new ServiceController(serviceName);[code]............

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"System.ArgumentException: An Item With The Same Key Has Already Been Added." When Trying To Order An In-memory LINQ Query By A LINQ Association?

Jan 27, 2011

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) = _

[code]....

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LINQ To SQL - Add In Row_Number To A LINQ To SQL Query?

Aug 31, 2011

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.

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VS 2008 Linq Possible To Use Query In Another Query?

Apr 16, 2011

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"

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Setup Linq To SQL Dynamically?

Jan 29, 2010

In my application I use Linq to SQL to communicate with my SQL database.To setup a connection I added a Linq to SQL class, selected a database and choosen a SQL table.After this I use the following code for showing SQL data:Using aw As New LinqtoSQLDataContext

Dim Data = From c In aw.TestDatabase_TestTable _
Select c.No, c.Description
DataGridView1.DataSource = Data
End Using

Now the link to the SQL database is hardcoded and the databasename must be used in every Linq-statement.Is it possible to make the link to the SQL database dynamic so I can switch easyily between a test and production database?Can the tablename inside the Linq statements be dynamic too?

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Pass Stored Procedure Name Dynamically To Linq-to-SQL?

Jul 11, 2011

How can I pass stored procedure name dynamically to Linq-to-SQL, vb.net and get the result into a datatable.

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Dynamically Select Table At Runtime With Dynamic LINQ?

Feb 17, 2011

I'm developing an application to allow engineers to conduct simple single table/view queries against our databases by selecting Database, Table, Fields.

I get how to use the Dynamic LINQ Library Sample to provide for dynamically selecting the Select, Where and Order by Clauses at runtime but I'm at an impass on how to allot for table choice.

Is there a way to provide for dynamically selecting the "from" table at run time

EDIT

So Both of the answers seem to be saying the same general Idea. I'm going to try to convert the C# into VB and get it to work.

The first answer converts to

NotInheritable Class DataContextExtensions
Private Sub New()
End Sub

[Code].....

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Sql - Dynamically Varied Number Of Conditions In The 'where' Statement Using LINQ?

Feb 3, 2010

I'm working on my first project using LINQ (in mvc), so there is probably something very simple that I missed. However, a day of searching and experimenting has not turned up anything that works, hence the post.

I'm trying to write a LINQ query (Linq to SQL) that will contain a multiple number of conditions in the where statement separated by an OR or an AND. We don't know how many conditions are going to be in the query until runtime. This is for a search filter control, where the user can select multiple criteria to filter by.

select * from table
where table.col = 1
OR table.col = 2
OR table.col = 7
'number of other conditions

Before I would just construct the SQL query as a string while looping over all conditions. However, it seems like there should be a nice way of doing this in LINQ. I have tried looking using expression trees, but they seem a bit over my head for the moment. Another idea was to execute a lambda function inside the where statement, like so:

For Each value In values matchingRows = matchingRows.Where(Function(row) row.col = value)However, this only works for AND conditions. How do I do ORs?

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.net - Should Use LINQ For This Query

Sep 4, 2009

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?

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Can Do A LINQ Query Of A LINQ Query?

Mar 24, 2012

Is it possible to do the following? [code] Basically I have one Load_Gridview function that is called on all postbacks, and rather than creating a bunch of different cases.I want the filters to stack.My actual code has more filters set up (4 or 5 of the).It all compiles ok but when I run and try to execute with active checked, or a department selected I get the following error. [code]

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Linq Query In .net?

May 5, 2009

I have below XML file

<?
xml version="1.0" encoding="utf-8" ?><
PageFlow>
<
attributegroup name="Search"><
attributes>

[Code]...

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Put A Sum() In Linq Query?

Apr 18, 2012

I am looking to sum the "Status" field.

Dim _detailRecords As New DataTable
_detailRecords.Columns.Add("y")
_detailRecords.Columns.Add("z")

[Code]....

I'm also wanting to keep this as an IEnumerable of DataRow because I will be creating a datatable from it with

Dim yyyyy As DataTable = query8.CopyToDataTable

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Query With Linq To Xm?

Aug 13, 2010

I am Fairly new to Linq and I am trying to write a simple query to return the error messages within my xml file.

<?xml version="1.0" encoding="utf-8"?>
<Error xmlns="urn:xxxxx">
The following errors were detected:

[code].....

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Why The Sql Query Is Different On That Linq Query When Run On C# And On .net

Aug 26, 2009

if I run this under c#

from p in Addresses where p.Address2 == null select p.AddressID

it generate this query

SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] IS NULL

if I run this under vb.net

from p in Addresses where p.Address2 = nothing select p.AddressID

it generate this query

SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] = ''

p.Address2 is a varchar field that accept null value

why vb.net is "wrong" ?

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