.net - Proper Syntax For LINQ Query Selecting Only Certain Columns?
Sep 13, 2011
What is the proper syntax for this:
Dim qry As <??> = From f In dirInfo.GetFiles("*.QBW") Select File = f.FullName, Include = True
Dim dt As DataTable = qry.CopyToDataTable()
I tried as "IEnumerable(Of DataRow)" but that didn't work. At runtime it said:
Unable to cast object of type
'WhereSelectArrayIterator2[System.IO.FileInfo,VB$AnonymousType_02[System.String,System.Boolean]]'
to type
'System.Collections.Generic.IEnumerable`1[System.Data.DataRow]'.
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Feb 15, 2010
I am using 1 listbox and 4 text box. I want to retrieve data from my database i.e. ms access database into listbox I am firing the select query by using this code on Page Load event and list box selecetedindex change event which is following.[code]...
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May 16, 2010
I am using 1 listbox and 4 text box. I want to retrieve data from my database i.e. ms access database into listbox I am firing the select query by using this code on Page Load event and list box selecetedindex change event which is following.
The following code is load in Page load event
Private Sub PopulateProductList()
Dim con As OleDbConnection
[code].....
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Dec 3, 2009
I am trying to AVERAGE 6 different fields on a DataTable, but without grouping. Just the AVERAGE. I have found a couple of examples in C#, but can't find any examples for how to do this in VB.Here is what I have so far:
Dim query = From dtRow In dtIn.AsEnumerable _
Where dtRow.Field(Of String)("FOLLOWUP") = "Alert" _
Select New With { _
.Brand_Functional_Avg = XXX.Average(Function(f) f("Brand_Functional")), _
.Brand_Personal_Avg = XXX.Average(Function(f) f("Brand_Personal")) _
}
What should I use for XXX? I tried all of the options that I could think of and nothing is compiling.
Trust me, if I could write this in C#, I would, but the project requires VB.
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Feb 25, 2011
I have a query that I cannot seem to replicate in expression method chain syntax. I have two tables "User" and "UserPayment". User and UserPayment have a one to many relation i.e. One User can have many UserPayments.
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Nov 4, 2010
The following data is created by joining two sql tables together:I would like to group together distinct rows of DateStamp/UserName/ StudentName/ InstructorName/TableName/PrimaryKey (I'll call this 'group records') and then group under these ColumnName/PreviousValue/NewValue (I'll call this 'subgroup records')The end result would be that I could iterate through the 'group records' - there would be 5. In each 'group record', I could then iterate through the 'subgroup records'. The 5 groups would contain 3, 2, 5, 2 and 1 subgroup records respectively.What would be the syntax to create a query to do this? Ideally this would be in a vb.net linq syntax.
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Apr 17, 2011
How to JOIN tables on nullable columns? I have following LINQ-query, RMA.fiCharge can be NULL:
Dim query = From charge In Services.dsERP.ERP_Charge _
Join rma In Services.dsRMA.RMA _
On charge.idCharge Equals rma.fiCharge _
Where rma.IMEI = imei
Select charge.idCharge
I get a "Conversion from type 'DBNull' to type 'Integer' is not valid" in query.ToArray():
Dim filter = _
String.Format(Services.dsERP.ERP_Charge.idChargeColumn.ColumnName & " IN({0})", String.Join(",", query.ToArray))
So I could append a WHERE RMA.fiCharge IS NOT NULL in the query. But how to do that in LINQ or is there another option?
The problem was that the DataSet does not support Nullable-Types but generates an InvalidCastException if you query any NULL-Values on an integer-column. The modified LINQ-query from dahlbyk works with little modification. The DataSet generates a boolean-property for every column with AllowDbNull=True, in this case IsfiChargeNull.
Dim query = From charge In Services.dsERP.ERP_Charge _
Join rma In (From rma In Services.dsRMA.RMA _
Where Not rma.IsfiChargeNull
Select rma)
On charge.idCharge Equals rma.fiCharge _
Where rma.IMEI = imei
Select charge.idCharge
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Feb 2, 2011
I'd like to take all suggestion either in C# or VB.NET.I have a DB diagram like the image below. I also include the database script here [URL]In the Students table, CountryId and RoomId column are allowed null. Because some records do not have info about room and country yet.Also, some students do not have essays.I'm doing a joint query with all tables. I want to select all students to project the result like this:Wanted query result.
Here's my current query that gives the result like the image below:
Dim db As New DBDataContext
Dim query = From st In db.Students _
Join c In db.Countries On c.Id Equals st.Id _
Join r In db.Rooms On r.Id Equals st.RoomId _
[code].....
current query result I got only one result back because I have (2) William NoMan record in every table. But I don't get anything about others, like (3) Sync Master who has everything but RoomId.What do I need to modify the query above so it will give me all students like in the wanted query image above?
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Apr 22, 2011
Anyone know the proper syntax for importing the VB6 Compatibility in .net?
Example:
Imports VB6 = Microsoft.VisualBasic.Compatibility.VB6
Doesn't seem to work anymore.
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Dec 21, 2010
Is this the correct syntax to delete a record from a dataset? [code]
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Jul 17, 2009
i did the following code:
[Code]...
but it does not work.... where is my mistake in the above code?
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Dec 31, 2009
Now I know whats going to happen, I will post a request for code syntax and one of the admins is going to say that I need to post the code I already have. The code I already have is irrelevant to what i wish to do. So, continuing on; I have a micro controller that i wish to send commands to it in HEX data type. Communication is via the serial port RS232. (well technically its through the USB to serial converter)Steps:
1) Sending a "001" tells the micro controller to await instructions as to what to set the duty cycle to
2) The data that follows i.e." 050, 010, 185 " will be added to 400 (by the micro controller) to come up with a duty cycle based on a 10 bit resolution of 0-1024. I am only going to be using the range of 401- ~500.
I can communicate with the micro controller via hyper terminal. Using the Alt + #keys method I can transmit data to the micro controller, and this is what i with to do with vb.net.[code]
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May 16, 2010
TextBox1.font.size = "8".Gives me an error.... what would be the proper syntax to define a font size in code.yes I know it can be changed in the properties but I need to know to change it in code too..
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Jan 17, 2010
I'm making a console game that shows some data:
#: Item Name Item Slot Cost Item Price
in that order. The thing I want to do is to make it come out in nice even columns...but I can't seem to make it do that. It comes it out in nasty uneven rows that don't look attractive...
Basically, here's what it looks like now:
1. Sword Slots: 2 Price: $40
2. W. Stick Slots: 4 Price: $1
I want to get each column to line up nicely with the other (since I control the size name).
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Dec 10, 2009
Using Excel Automation classes I am seeking to save an Excel file as a delimited text file. The examples given in the MSDN library refer to versions older than Express 2008 with (apparently) different syntax options for FileFormat.Based on the snippet shown, I get a COM exception error (800A03EC). Other variations produce the same error.
Am I improperly applying the Automation features?
Imports System.IO
Imports Microsoft.Office.Interop
[code]....
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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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Nov 9, 2011
Given the xml below why does the first selectsinglenode call not work but the second one does? Are the single quotes specifying a string type or something?
Dim dbglvlnode As Xml.XmlNode = doc.SelectSingleNode(String.Format("Config/Scanner[DeviceID = '{0}']/DebugLevel", XMLstuff.DeviceID))
Dim dbglvlnode As Xml.XmlNode = doc.SelectSingleNode(String.Format("Config/Scanner[DeviceID = {0}]/DebugLevel", XMLstuff.DeviceID))
<?xml version="1.0" standalone="yes"?>
[Code] ......
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Feb 27, 2012
I'm tring to create chart from Column B (to be X axis), and column D (Y axis).when I set it as range: .range("B":"D") - it'll take also column C.How can I set range for chart to be column B and D only??
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Oct 31, 2011
I have 7 company Divisions that sit in an access database.I then use this list to populate two comboboxes in my windows form.However I get a syntax error in my SQL Query if the Division name is more than one word.For example in my access database I have two columns one is a status column and the other is a division column. If for example the Division is called 'Corporate' the status column is called 'Status Corporate' and the division column is called 'Corporate'.The SQL query works fine in this scenario.However if I have a Division that is more than one word, lets say 'Operations Division' I get an error in my SQL Query that says -
Quote: Syntax error (missing operator) in query expression 'Operations Division'.Here is my code
sqlNewTenderDetails = "SELECT " & Me.DivisionBox.SelectedValue & " From BidRefCodes Where " & "[Status " & Me.DivisionBox.SelectedValue & "='Active'"
daNewTenderDetails = New OleDb.OleDbDataAdapter(sqlNewTenderDetails, NewTenderDetailsTableCon)[code]....
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Feb 10, 2012
ames tile1 to tile 100Array is loaded from a textfile of 10,10 (not stored as a 10,10 just parsed from line to line, which I feel needs to be changed asap)Each tile is then given a corresponding graphic (e.g. grass, water, lava) and soon hopefully I will add interaction with certain tiles
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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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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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Jan 17, 2012
I am using a Strongly Typed Dataset as DAL. I want to return a single column from my table for that i wrote the code as
SELECT DISTINCT Floor
FROM Room
WHERE (Building = @Building)
But when i previewed the data, it shows me all the columns of the table with Null Value and the column with primary key has -1 value. This condition raise an Exception when i link this query to a ComboBox ..
cmbFloor.DataSource = da.GetFloorByBuilding(cmbBuilding.Text)
cmbFloor.DisplayMember = "Floor"
Error: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
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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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May 12, 2012
I'm trying to learn the query structure. I have the following XML:
<?xml version="1.0" encoding="utf-8"?>
<list>
<item>
<due>07 May 2012</due>
[code]....
And I'm trying to delete <item> elements with a query:
Dim DeleteItems = From e In Root.Elements("list") Where e.Element("name").Value = Text
However it isn't working. I think it's trying to select tags called <item> in the file's root, however it needs to be selecting <item> tags in the <list> element - which I don't know how to do.
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Oct 24, 2011
I have a DataTable with about 64 columns, including "UserAnswer", "CorrectAnswer", and "QID_Lookup". I am building a LINQ that will select all the rows that have a correct answer (user answer matches correct answer), but I only want to select rows that have distinct "QID_Lookup".
[Code]...
The problem is that the result set includes duplicate QID_Lookup values. How can I include only distinct QID_Lookup values? keep in mind that there are 64 columns, so if I can avoid it, I wouldn't want to list each column individually for selection.
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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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Oct 19, 2009
I am trying to write some Linq to SQL that will bring me back a list of rows containing a single instance of BaseQuestionIDs but I want the row with the highest version, so, from the following table of data:
Id CreatedDate Version BaseQuestionID
2 2009-10-07 13:47:27.687 1 2
3 2009-10-07 13:49:35.010 1 3
4 2009-10-09 16:03:45.973 1 5
[code]...
I want to return:
Id CreatedDate Version BaseQuestionID
2 2009-10-07 13:47:27.687 1 2
3 2009-10-07 13:49:35.010 1 3
[code]...
I have tried a variety of things, but have not nailed it yet. I am working in vb.net?
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Jul 14, 2009
tell me the equivalent syntax for the following code in VB.net?
Static Class TestList
{
static void Main()
{
[code].....
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May 4, 2011
I ran into this answer which had a triple dot syntax in VB.NET that I have never seen before. The query looks like this
[Code]...
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