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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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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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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Jun 18, 2011
I'm currently attempting to use a .NET WebBrowser to display help information (stored locally in html files) for an application I'm writing, however I'm experiencing two problems, both related to hyperlinks.
Firstly, I have a search function which returns the correct URL in the format file:\C:... I can copy and paste it into a browser, and it will navigate there. Yet clicking on the link within the control itself does nothing at all.
Secondly, the HTML files all contain relative paths to other HTML files. These of course do not work as I just end up with file:\C:help.html which gives me a 'webpage is unavailable.' But I can't think of a way to get it to work without parsing the HTML file and concatenating the path to the directory on to the front of the link.
Just to clarify, in the first problem I am dynamically building a search result page as the user types. The HTML contains several results similar to this (yes, it's unfinished, I'm just showing you the link part): [code] Now, when I click on that link in the control nothing happens, it doesn't give me a 'webpage is unavailable' or take me to the actual page. Saving the HTML, however, and opening it with Chrome, IE and Firefox works fine.In the second problem, I have a different help file for different sections, each containing relative links to several others. VB picks these up as direct paths, and attempts to go there from root, i.e file:\C:file.html. The only solution I can think of is to parse the file and use WebBrowser.Navigate(Path.Combine(pathToDirectory, nameOfHelpFile.html), which seems a lot more inefficient than it should be.
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Mar 16, 2011
I 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.
[Code]...
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Oct 20, 2011
I 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.
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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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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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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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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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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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Oct 14, 2009
Below the xml doc
<Root>
<Global>
</Global>
<local>
<section name="A">
<subsection name="A">
[Code] .....
Now I want the property1 whose section name="B" and subsection name="B" and innersection name="B" in one single query using linq to xml.
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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
[code].....
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Jul 23, 2010
I have a VB.NET search routine, part of which is provided, below, that checks all Text cells in a DataGridView for a given string (inclusive), using a basic set of nested loops to perform the search:
' Search for the first occurrence of the given string
For Each row As DataGridViewRow In dgvMembers.Rows
' Skip the new row
[Code].....
is there a way to replicate this behavior using LINQ? Basically I would like the query to select (or return) the first DataGridViewCell whose text contains the search string. I've done some tinkering with sub-queries and the like, but I'm still having trouble wrapping my brain around the concepts (too many years of writing T-SQL, I guess).
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Jul 1, 2009
Is there an easy way of dynamically building a filepath in .Net? At the moment I'm building the filepath by concatenating various strings (from application settings, user input and Date.ToString) but this relies on there not being double '' characters or illegal characters etc in the strings. Obviously I can manually validate the strings for this sort of thing but I was wondering if there was something built into .Net that can handle this.
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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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Sep 24, 2011
How would I go about counting the number of times a given query occurs inside of a text file using LINQ?I need to search through the attached file and see how many justices were appointed by each president, and then create a new text file displaying the following:
presName, justiceCounter 'president name ordered by first name, number of justices appointed
I pretty much get how to do everything except for keeping an accurate counter within the LINQ query. However, I do feel confused about the order in which I should write this code, as in where I should keep my counter for how many justices a given president has appointed.
My output is displaying like this:
Abraham Lincoln,111
Abraham Lincoln,111
Abraham Lincoln,111
[code]....
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May 9, 2012
I want to create a LINQ to entities query getting data(join) out of two tables and bind the result as datasource to a datagridview.
Unfortunately I seem to stumble upon a syntax issue.
Table 1 : dcpricing.tblpricing
Table 2 : dcpropertydetail.tblpropertydetail
Grid: grdpricing
[Code].....
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Nov 15, 2011
I am trying to do a search on a index/row number taken from a dataview i.e. I enter 379437 in the input box which I know has a index/row number of 6. Now when I replace the Rows(index) with a Rows(6) I get the results that I want. When I run the code below the index comes out as 75 which displays the first row from the dataset which is a completely different set of results.
[Code]...
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Oct 26, 2009
I 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:
[Code]...
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Jan 24, 2012
I am building an xml file with the help of Linq queries and I'm not sure why the code below doesn't work.[code]
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Sep 24, 2011
I wanted to know how to write a query in data grid control. So far I've seen alot of forums but they are related to either 2008 vb or vb 6. how to write a query in the datagrid control which will search for an id in the database of access and present it.
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Jan 4, 2011
I 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?
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Dec 12, 2010
I'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)"
[Code]...
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Dec 5, 2011
I can usually find the answers to most of my questions via the Google Gods, but not this time.I have a form that has a TabPageControl and on that page a collection of labels and text boxes via a usercontrol.
On the form I have a button that allows the user to create a new tabpage, when the code adds a new page, it automatically adds the UserControl collection. I can't get my head around how to access the objects on the newly created tabpage.
What I need to be able todo is take the index of the tabpage that has focus and translate that against the UerContol name, but I havn't a clue how to do it!
[Code]...
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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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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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Mar 7, 2011
I 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:
[Code]...
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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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