Is there a way to convert a string into a linq query? Searching for those words brings up tons of stuff unrelated to what I'm trying to do..For instance, this works, of course...
Dim lstMyQuery = (From item in htMyTable.values where item(0) = "Apple" Select item)
But somehow I want to do this:
Dim strQuery = "From item in htMyTable.values where item(0) = " & CHR(34) & "Apples" & CHR(34) & " Select item"
Dim lstMyQuery = (Somehow run/convert strQuery as a query)
The reason is strQuery will be different each time depending on what the user has selected earlier in the program.R if lstMyQuery is already a collection, is there a way to add to it?
Dim lstMyQuery = (From item in htMyTable.values where item(0) = "Apples" Select item)
(this obviously doesn't work, but it's basically what I want to do...)
lstMyQuery.Add(From item in htMyTable.values where item(0) = "Oranges" Select item)
I have the following routine (that works) but which is messy to update owing to the hand-typed strings it uses:
Private Sub ListDefaults() Dim conn As New SqlConnection( _ "server=bas047AUTODESKVAULT;Database=DWGDetails;Integrated Security=SSPI") 'Dim conn As New SqlConnection( _
I've created a small WPF app in VB9 to catalog our sizable DVD collection. This exercise has been more about learn programming than the need to have a movie database app, but I digress.The SQL database I created has a field for "Genre" that does not have an entry for all the movies in our collection. As such, when I run the method that filters the movie listing by "Genre" the compiler throws the "StrongTypingException was unhandled" error stating "The value for column 'Genre' in table 'Movies' is DBNull.".
I now understand where the DBNull problem comes from and have been searching for several hours to find a VB solution that converts the DBNull fields to strings on the fly during the LINQ query. I've found many solutions people have tried but, since I'm quite new to all this, none of them have worked for me. Pasted below is the method that throws the exception.
I am new to LINQ, how to convert the following SQL query to LINQ? SELECT Date,ShiftName,Max(Score) AS Score, 1 AS IsPreferred FROM Temp_Nurse_Fill_RequestNumbers group by ShiftName,date
SELECT EqID, MakeID, Model, Description, (SELECT MAX(EvDateEnd) AS MaxOfDateEnd FROM tblEvent WHERE (EqID = tblEquip.EqID) AND (Event = 'REG')) AS RegExpire,
[code]....
For example, I want to get the Max EvDateEnd from the Events table for each record in tblEquip, but not all records in tblEquip have the "REG" event, while others have multiple REG events.Some events (like EAE) I leave the tblEvent.EvDateEnd field blank to show the event is open and ongoing, such as issuing a vehicle to an employee(entity). when the vehicle is returned I enter the date in EvDateEnd essentially closing the event.
GOAL: Bind nested ListViews to LINQ generated iQueryable of anonymous type. I want to use LINQ because you can use GroupBy and bind the nested ListView to the 'it' keyword.
SETUP: I have groups of sets of conditions. Each set of conditions is stored in the BillingCodes table. Each group of BillingCodes is stored in the BillingGroups table.
I have a custom object that stores the ID, Name, and NumCodes for each BillingGroup that the user has chosen.I have a collection of these objects called GroupsList that has a list of the groups that the user has chosen.
Problem 1: I can iterate through GroupsList and grab all the IDs. How do I translate the SQL 'WHERE ID IN(a string of comma delineated IDs)' for LINQ to SQL? Is that the best way to do that?
Problem 2: Once I have the list of BillingGroups I need to iterate through each group. For each group, I need to iterate through the BillingCodes. For each BillingCode I need to generate a WHERE clause that has all of the conditions in the BillingCode. I propose something like so:
for each BillingGroup in BillingGroups for each BillingCode in BillingGroup.BillingCodes where1 = "..." next next
Problem 3: Here's the part where I don't have a clue. I need to dynamically create a query in LINQ to SQL. Keep in mind that I don't know how many groups there'll be or how many codes are in each group.
I'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.
I'm using LINQ to SQL to query some data.Here's my Employees table colummns:
-FirstName (or givename i.e. John) -LastName (has middle name and family name seperated by space i.e. Mac Tenny
Some people have middle name and some don't. Here's some sample data.
-FirstName LastName John Mac Tenny (with middle name "Mac") Mike Mika (no middle name)
[code]....
I want to query for people who have their middle or last name started with search criteria. Here's how I search for employees with middle name started with "joe" :
query = From emp In db.Employees _ Where emp.LastName.StartsWith("joe") _ Select emp
How do I query for employees with family name(last part of the LastName) started with "joe"?
I am using a path comparison to find any children tags which works well when there is only 1 tag selected. This is my code for when multiples tags are selected but it is not working. Can you point me in the right direction?
Single Tag Selection (working) Dim tagpath = uxTags.SelectedItem.Text lnqCases = From i In lnqCases Where i.HelpDeskTagItems.Any(Function(x)
What I'm trying to do is to write a generic rss reader that I plug in any URL into without worry if the feed has all the common properties. For instance in my example below I'm looking for pubDate, however if no pubDate exists in the xml I'd like to return the current Date. I cannot seem to get the syntax right though.
Dim xmldoc As New XDocument xmldoc = XDocument.Load(url) Dim feeds = From feed In xmldoc.Descendants("item") Select New With { _
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"
I have this query that returns the number of rows which is :
SELECT COUNT(*) AS MemberTotal FROM Members
i'm trying to write a readonly property called count to return that value in string its suppose to display the result of my query in a tool strip status label, I have this in my code
Public ReadOnly Property count() As String Get Return memberAdapter.GetMemberCount() End Get End Property
but it gives me an error saying I can't convert dataset to string something like that and I don't have any idea on how to convert it I tried the Cstr but that didn't work?
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 encountered something like a logical error which I could hardly resolve since I'm new to this technology. I'm using visual basic 2008 express edition with its built-in linq-to-sql technology. I was able to retrieve, add, edit, and delete such record using the linq-to-sql method, but one thing.I could not get is something like relational database operation. Here is my problem. As you can see the table above which represents the records on my database. You can notice there some account numbers that were duplicated which I used as the primary key or identifier. What I want is when I'd like to query such account number it should display all the records that have the same account numbers on it. Say for example, if I query the account number 00003. It should only pull up and display three records with the name Maverick and their corresponding address, movie rented and date.What is happening in my end is when I query such account number which are being duplicated in the database I encountered two things, its either it would display all the records in the database with different account numbers associated or it gives me an error message if I change my code from 'For Each memrec In db.Table3s' to 'For Each memrec In retrn' statement.What I've been trying to do here is if you enter the account number on the search box, it should only display the records on the combo box associated with the account number being entered. Like if you enter 00003 on the search box, it should only display the three movies rented by Maverick no more no less on the combo box. [code]
I have already tried that set of codes before but it's working the same thing. I tried many times modifying my codes before I posted my comment in this forum thinking that i can resolve it on my own but I wasn't able to. That code won't still filter the records in the database. I would like to verify that the table above is only representation but the real column on the table on my database is 'Account#' not Account Number and visual basic would detect the code as 'Account_'. May i know why Movies_Rented column on my table is not a member of string? Why is it the code you gave would still display all the records on the combo box? this is what im not getting. hope you can still find the solution to this issue.
i need to query the datatable & set the outcome as datagridview controls datasource
vb.net Private Sub Txt_Search_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Txt_Search.TextChanged 'routine objective:- Filter datatable & set the datagridview datasource
I'm just getting my feet wet with LINQ but am struggling to convert this SQL statement to LINQ.
Dim SQLString As String = "SELECT MESSAGE_ID FROM " & Schema & _ ".PPM_TRANSFER_EMAIL WHERE TO_CHAR(IMPORTED_DATE,'YYYY/MM/DD') <= '" & _ DeletionDate.ToString("yyyy/MM/dd") & "' AND IMPORTED = 'Y' AND FILE_NAME LIKE '" & _ mb & "%'"
I have a Dataset that already contains all the data from the PPM_TRANSFER_EMAIL table so it seems silly to query the database again when I can use LINQ to query the dataset.
If I use a LINQ query over some type of collection, is there any way to know the initial index of an element of the result?
Purpose: I make a query to set as source of a DataGridView, and on a (button)cellclick event I want to a call a method that needs to reference the collection at the correct index.
I have a LINQ query that groups and counts on a single dgv cell. What I want to do is group and count on 2 dgv cells. So I modified my existing query by adding a SELECT statement highlighted :
CODE:
But I am getting an error on the second select variable stating: Range variable 'Value' is already declared
What I have read shows that I can select more than one variable.
I'm trying to do a LINQ Query against a typed datatable that will return me duplicated data.With out going into too much detail, here's the basic setup:
strCode1 - string type intCode1 - int32 type intAdjustor - int32
There are more fields but these are the ones that are important.I'm going to do my best to describe this, as it's kind of confusing.In theory intCode1 is a key for strCode1 (hence the names). So each time intCode1 is duplicated, the same strCode1 should appear. Example:
[code]...
Ultimately I'd like to get a List(Of T) - where T is my typed data row. In SQL, I would simply use a sub query, to get a distinct list of strCode1 and intCode1, then do a count, grouped by strCode1 where I get more than one row.I'm not sure how to translate that into LINQ, AND get the original types data rows returned in a list.
I'm using a DataGridView to post the results of LINQ-from-SQL query. I was hoping that the data would be editable in the DataGridView, but it isn't. I made sure that DataGridView.readonly = false. I'm using VB.
VB 2008 DB = New CXToolDataContext() Dim Systems = (From TBLSYSTEMS In DB.tblSystems, TBLSYSTYPES In DB.tblSystemTypes _ Where TBLSYSTEMS.ProjectName = projectnumber And TBLSYSTEMS.SystemType =
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
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."
