Building A Dynamic LINQ Query
Mar 16, 2011I have a listbox which users can select from a list if Towns, I want to be able to build a LINQ query based on the selected items in the list e.g.
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.net - ActiveRecord Linq/NHibernate Linq Not Building Query Completely?
Jul 14, 2011given 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
Dynamic LINQ Query Based On Dynamic Number Of Comboboxes?
Feb 5, 2010I would like to bind a DataGridView to a different LINQ query every time (in order to reuse the same form/DGV for different queries), like this:
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but the "Qry", and the number of comboboxes, and their field names would change every time.
Dynamically Building LINQ Query Using OR Operator In VB
May 22, 2009I 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
VS 2010 Dynamically Building LINQ Query To Search Objects
Mar 24, 2011I 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:
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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.
LINQ Query Using The Dynamic LINQ Library?
Mar 31, 2011Forgive 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."
.net - Dynamic Linq Query?
Mar 14, 2011I have been trying the following but it returns unexpected results:
Dim xd As XDocument = _
<?xml version="1.0" encoding="utf-8"?>
<root>
[code].....
The above result returns both 'element' nodes however it should only return the first where element/subelement@id=1/subsubelement@id=3 However if results.Ancestors. is used it returns the correct 'subelement' and if that line is not included it returns a single 'subsubelement' whih is also correct I don't understand why when mvoing to the 'element' it returns both (I realise both have a subelement with id=1 but I thought each further query would filter out the presvious results)?
Dynamic Query Linq To Xml?
Mar 16, 2011I want to write a query that the "where" in the query is a string something like"
Dim query as string= "Name =xxxx and Date > 10 "
Dim t = from book in doc.Descendants("books") Select _
[Name] = book..value, [Date] = book..value....
Where (query)
I build the query string on run time
C# - Linq Query With Dynamic Where Clause?
Apr 13, 2012I'm need to do the equivalent of a t-sql statement like this using LINQ:
SELECT * FROM mytable WHERE idnumber IN('1', '2', '3')
so in LINQ I have:
Dim _Values as String = "1, 2, 3"
Dim _Query = (From m In mytable Where idnumber = _Values Select m).ToList()
Not sure what to do with _Values to make idnumber evaluate each value in the string.
Linq Dynamic Query Program?
Aug 9, 2010How do i great dynamic linq query in VB.net?
View 3 RepliesVB Dynamic Run-Time Query With Linq And Lambda Expressions
Mar 16, 2009I have an untyped dataset returned from my WebService. The user wants to dynamically construct a query referencing tables and columns and specifying values to test for.I have looked at Lambda Expressions and the Expressions.Expression Namespace. I think these provide the answer I'm looking for, but I'm not certain how to go about contructing the linq expressions to extract the datarows I'm looking for.
I plan on limiting the result to one datatable that the query will result in and i"ll provide the joins from the user's constructs.For a simple example I have a DataTable with (n) rows called "Table", and in it there is a computed column called "b_IsActive" that has the expression "Convert(IsActive, 'System.Boolean')". The user wants to retrieve all rows in "Table" where field "b_IsActive" is true.
C# - Use Meta Tales Or Table Names To Construct A Dynamic Query In LINQ?
Feb 8, 2011Is there a way to use Meta Tales or Table names to Construct a dynamic query in LINQ?
foreach (var metaTable in db.Mapping.GetTables())
{
var queryType = metaTable.RowType.Type;
[code]....
Is there a way to do something like this? The attempt above yields the error:Could not find an implementation of the query pattern for source type 'System.Data.Linq.ITable'. 'Select' not found. Consider explicitly specifying the type of the range variable 'q'.
Convert A Two-table Exists Query From SQL To Linq Using Dynamic Fields In The Subquery?
Jun 7, 2011I'm trying to query old Access database tables and compare them with SQL Server tables.They often don't have primary keys, or they have extra fields that had some purpose in the nineties, etc., or the new tables have new fields, etc.I need to find records - based on a set of fields specified at runtime - that are in one table but not another.So, I do this kind of query all the time in SQL, when I'm comparing data in different tables:
dim fields_i_care_about as string = "field1, field2, field3"
'This kind of thing gets set by a caller, can be any number of fields, depends on the
'table
dim s as string= ""
[code]....
It tells me it can't convert a Boolean - Is there any way to do this without Linq expressions? They seem far more complex than what I'm trying to do here, and they take a lot of code, and also I can't seem to find examples of Expressions where we're comparing two fields in a subquery.Is there a simpler way? I know I could do the usual EXISTS query using JOIN or IN - in this case I don't need the query to be super fast or anything. And I don't need to use a DataTable or DataSet - I can put the data in some other kind of object.
Exception When Building LINQ Query With Multiple Levels Of Delegates Or Lambdas ("Value Cannot Be Null. Parameter Name: Instance")?
Jun 22, 2011've got a function that takes two parameters (a delegate and an integer) and then creates a LINQ MethodCallExpression, which it uses to gets the results:
Public Delegate Function CompareTwoIntegerFunction(ByVal i1 As Integer, ByVal i2 As Integer) As Boolean
Public Function Test(ByVal pFunc As CompareTwoIntegerFunction, ByVal i1 As Integer, ByVal
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.net - Write A Linq To Sql Query To Find Records Where Field Name Can Match One Of Dynamic Number Of Strings?
Mar 21, 2012I have users check off lab facilities in a UI. I want to use linq to fetch corresponding records for all of the labs that they have checked off. Basically,
Dim myRecs = (From l As EpiData In myDataContext.EPIDatas Where l.facility= _
one of the checked labs
So basically, I need to write a linq query where the "strings" to match are determined at runtime. Is there any way to do this easily? I know that there is a library out there called dynamic LINQ, but (1) it's in C# and I'm writing in VB (2) I'm really just looking for a single, simple solution for this single case.
Building A Dynamic Regular Expression?
Jun 12, 2009I'm attempting to build a function that will return a regex that is dynamically created.The regex to create will be a range check between two numbers. So far I've got something similar to this (not finished as yet).Is this approach valid, or is there an easier way that I'm overlooking?
Public Shared Function Range(ByVal Minimum As Integer, ByVal Maximum As Integer) As String
Return "^([" & Minimum.ToString.PadLeft(2, "0") & "]" & Microsoft.VisualBasic.StrDup(Minimum.ToString.Length, "[0-9]") & "|2[0-4][0-9]|25[0-5])$"
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Building A Dynamic Sqlconnection String?
Jul 14, 2011Imports System.Data.Sql
Imports System.Data.SqlClient
Imports System.Configuration
Module Module1
[code].....
this is my connection string on my pc how can i make this as a dynamic connectionstring so i cant remove the db and get a new connectionstring?
LINQ Query Is Enumerated - Turn On Some Kind Of Flag That Alerts Me Each Time A LINQ Query Is Enumerated?
Sep 22, 2009I 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.
Dynamic SQL To Dynamic LINQ In .NET With MS SQL Server 2008?
May 24, 2010I need to represent the following query using LINQ:
DECLARE @PurchasedInventoryItemID Int = 2
DECLARE @PurchasedInventorySectionID Int = 0
DECLARE @PurchasedInventoryItem_PurchasingCategoryID Int = 3
DECLARE @PurchasedInventorySection_PurchasingCategoryID Int = 0
[code]....
Now, I know that a query in .NET doesnt look like this, this is my test in the SQL Design Studio. Naturally VB.NET variables will be used in place of the SQL local variables.My problem is this: All of the conditions after "WHERE" are optional. In that a query might be made that uses one, some, all, or none of the conditions. V.PropertyID and V.Value can also appear any number of times.In VB.NET I can make this query easy enough by simply concatenating strings, and using a loop to append the "V.PropertyID/V.Value" conditions.I can also make a Stored Procedure in MS SQL, which is easy enough.However, I want to accomplish this using LINQ.
Building A DNN Module Using Linq To SQL
Oct 26, 2009I am building a module using linq to SQL and I am running into some problems. I have been following Michal Washington's tutorial on [URL]. The problem is that VB does not recognize my Complaint Class when I try to create new Complaint object. why I am unable to Dim a Complaint object? Here is my code:
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How To Get Lamda In LINQ To Actually Filter For Dynamic Linq
Sep 10, 2009Example-I have a person class
Public Class Person
Private _fname As String
Public Property Fname() As String
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Syntax Trouble Building Xml From Linq
Jan 24, 2012I am building an xml file with the help of Linq queries and I'm not sure why the code below doesn't work.[code]
View 1 RepliesBuilding A Query In A VB Program?
Jan 4, 2011I am working on a program. I created a database and used it to create a dataGridView in my program. I clicked the table adapter for the program and tried to create a new query. When I did this, I got the following error messages...Error message-the new command text returns data with schema different from schema of the main query check your query's command text if this is not desired Schema returned by the new query differs from the base query I cannot create a query for the database. What is a base query and what can I do to fix this?
View 7 RepliesProvlem With Building Query With Xml?
Dec 12, 2010I'm using the code below to search in XML files depending on the values entered in the text boxes, problem is I don't know how to combine the search statement with an "AND" when the users enter data in both textboxes. Can you please help me solve this problem? I am using VB.NET (VS 2008). Error "column can't be found is on line "Dim DV As New DataView(dt, "Receiver like " & "'" & C1TrueDBGrid1Donor.Columns(1).Value & "'" & "", Nothing, DataViewRowState.CurrentRows)"
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Performance Gain In LINQ Query Vs LINQ Stored Procedure?
Aug 6, 2009if there is that much of a performance gain in running a LINQ stored procedure versus a LINQ query?
View 1 RepliesAsp.net - Complex Linq Query - Add A .Where() Or .Any() Predicate To Reduce Query Complexity (in VB)?
Sep 14, 2010I 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
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Asp.net - Building A Valid SQL Query With Optional Parameters For Search Function?
Oct 20, 2011I have a search function de build.We are using pure ASP.NET w VB.NET We have multiple DropDownLists and we're building a search query with whatever was selected in those DDLs. My question is, how can I handle the blank values (unselected dropdownlist values) with the SQL Query ? I'm using AND operators in the query so if anything is blank it'll fail the search. If the dropdownlist has no selected value, i don't want the value to be part of the search. It would be easy to code with just 2-3 parameters, but we're looking thru at least 10 items and doing a SWITCH CASE or multiple IFs would soon become mayhem.
View 1 Replies.net - Building A LINQ Expression To Find Items Related To All Descendants Of A Tree Node?
Mar 7, 2011I have built a database structure that represents a category tree to help classify some of the data we have stored. The implementation is that each record in the Category table has a nullable foreign key back into the Category table to represent the parent Category of this category (one-to-many), essentially allowing for subcategories within a broader parent level. There is a CategoryMembership table that links a record in the Item table to its respective Category (many-to-many). I have created the DBML for this database, and it has a member access structure that includes the following:
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Dynamic Where In Linq To SQL?
Sep 14, 2010How would I get something like this to work so that I can dynamically alter the where-clause in this linq to sql query?
Dim AccountID = 1234
Dim AccountList
Select Case Types
[Code]....
With the above code I get this error:
Late binding operations cannot be converted to an expression tree
"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, 2011We 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]....
