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
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.
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"), _
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]...
'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
I am connecting to an Access database and using a parameter query with the LIKE operator to return all rows that match query. The string to search for is taken from a Textbox
sql =
"Select * FROM Allview WHERE Info Like" & "*" & CStr(TextBox1.Text) & "*" The query does not return any data in vb, but when run from access with same string, there is data returned.The connection to the database is done correctly, as I am able to return data with various other queries.
Partial code : Dim con As New OleDb.OleDbConnection[code]....
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.
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.
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.
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:
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?
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)"
I am attempting to retrieve records from a table of insurance companies via code in the application I am writing. tblInsuranceCompanies is a table in an Access 2007 database.In the application the SQL query retrieves no records and does not produce an error. The code is in a Try Catch code block.When I walkthrough the code, I can view the content of the Sql statement. I can copy this and paste it into Access directly-- the result giving me two records.[code]...
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
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.
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:
I've got a problem in one of my SQL queries, the type GUID can't be used with the operator & (obviously from the title). Here's the few lines of code which I'm using:
Dim ClientsAssetID As Guid = New Guid(ClientsAssetIDTextBox.Text) Dim Client1 As Guid = New Guid(Client1TextBox.Text) Dim Client2 As Guid = New Guid(Client2TextBox.Text)
[code]....
ClientsAsset, Client1, Client2 and Client3 are all of type GUID, but are entered into the textboxes as strings, are converted to guid and then should all go smoothly into the query, but it's having a problem with linking everything together. The error I'm getting is "Operator '&' is not defined for types 'String' and 'System.Guid'.How do I fix this? I've tried a few different things, such as using Ctype in the query, but they have also circled back to this error.
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."
I have been working at this for awhile, searching everywhee, I keep getting the error: Syntax error (missing operator) in query expression 'UPC Code=051384628502'.The block of code this error originates from is: [code] When I make it into a comment, the program works, except it doesn't put the string value I want into the table, nor does it save it.
Function updateCoustmers(ByVal ID As String, ByVal codeq As String, ByVal nameq As String, ByVal birthdateq As String, ByVal addressq As String, ByVal mobilenumberq As String, ByVal phonenumberq As String, ByVal certificateq As String, ByVal dateofregisterq As String, ByVal nameofcourseq As String, ByVal priceofcourseq As String, ByVal
[code]....
this is wrong message shown to me ( Syntax error (missing operator) in query expression '[ID]='. )
i have to complete a room reservation projecti have a database called project21.mdb and there is 3 table inside rooms,users,and bookingsnow i facing a problems on display my filter data on the datagridview1 ,it appear syntax error(missing operator).this is my code ..i think the problems is appear in this line,but i just cant find the problemsDim cmd As OleDbCommand = New OleDbCommand("SELECT type,startdate,enddate,starttime,endtime FROM rooms,bookings WHERE[code]......
i am getting error while inserting record in ms access here is my sample code
Dim str As String cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:final.mdb;") cn.Open() str = "INSERT INTO 019loan (Salutationinteger,Customername,shortname,
I am using vb.net 2003 and accessing an Access 2002 database via oleDb and Jet 4.0.I am filling a set of text boxes with data from the database. The Connection, DataAdapter and DataSet are all set using the Wizard. The text boxes fill correctly with the first row of data. I then wished to filter the data so I went into the code and added a WHERE clause as follows:WHERE [Boat Name]=" & xid & "xid is the variable name given to the selected boat name. When I run the program I get the following error message:
