Dynamic Variables In Linq Select Statement?
Nov 23, 2009
I have a listbox that is dynamically filled by certain values depending on what table has been selected from another list box. Once a value is selected, it is being graphed vs a date & time range. With my ignorance of linq: depending on what value is selected, the linq to sql statement I need to create to grab data from my database is different as I can't use an index on an anonymous type.
result = From t In db.APS _
Where t.DateTime >= startDate And _
t.DateTime <= finishDate And t.Weight = weight _
Select t.DateTime, t.TotalConcentration
t.TotalConcentration should be selected if my listbox value is "Total Concentration", but if it's something else, like "Temperature" or "Flow Rate" (connected to appropreate database columns) - this method obviously isn't going to work. I need to be able to dynamically select a specific column from the anonymous type list, or use some other method I'm unaware of to do this.
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Jun 24, 2011
I have the following SQL:
[Code]...
I want to put it (the select count statement) in this LINQ statement so I can get the sales count in my linq statement: Dim TheLeads = (From L In DB.Leads Where L.IsDeleted = False Select L).ToList() Is this possible to do in LINQ?
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May 18, 2012
Dim gg = From gs In AllData_TableList Order By gs.Biology Descending, gs.ChemistryDescending, gs.English Descending, gs.Frensh DescendingAll I need is to make this Statement order Dynamically like this
Dim Variable1 as string=Biology
Dim Variable2 as string=Chemistry
Dim Variable3 as string=English
[code].....
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Nov 18, 2009
While measuring the select case performance I encounter a strange behavior of Select Case statement with the constant expression. I don't understand why its behavior is dependent on the values to be compared.
[Code]...
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Feb 17, 2011
I'm developing an application to allow engineers to conduct simple single table/view queries against our databases by selecting Database, Table, Fields.
I get how to use the Dynamic LINQ Library Sample to provide for dynamically selecting the Select, Where and Order by Clauses at runtime but I'm at an impass on how to allot for table choice.
Is there a way to provide for dynamically selecting the "from" table at run time
EDIT
So Both of the answers seem to be saying the same general Idea. I'm going to try to convert the C# into VB and get it to work.
The first answer converts to
NotInheritable Class DataContextExtensions
Private Sub New()
End Sub
[Code].....
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Jun 5, 2008
I've recently ported my website from 2005 to 2008, and I'm using LINQ Queries to implement a search. The issue is that none of the fields are mandatory, so I've had to implement a dynamic LINQ Query (sic?). Here's the relevant code -
Public Function searchQuery(ByVal titleType As String, ByVal titleName As String, _
ByVal configMgr As String, ByVal lifecycle As String, _
ByVal CIType As String, ByVal recordsPerPage As String) As IEnumerable(Of
[code].....
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Dec 14, 2009
I have this LINQ statement [code]...
Is there any way that I can use if/iif within select ?
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Feb 5, 2010
I 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:
[Code]....
but the "Qry", and the number of comboboxes, and their field names would change every time.
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May 24, 2010
I 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.
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Sep 10, 2009
Example-I have a person class
Public Class Person
Private _fname As String
Public Property Fname() As String
[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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Jun 23, 2010
A co-worker wants to convert the following IfThenElseIf statement into a Select Case statement.
Explain why this is not possible.
If temperature = 100 Then
X = 0
ElseIf population > 1000 Then
X = 1
ElseIf rate < .1 Then
X = -1
End If
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Dec 3, 2008
I need to create a label for every cell in excel that has a value depending on search criteria.Depending on what number is searched i need to display all cells in the row in different labels. There could be one label that needs to be created or many.Do i have to have each variable named differently or can i just use one label tag and give each label a different label.location = (x, y).
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Apr 29, 2011
I have to perform calculations dynamically in ASP/VB.NET (Possibly SQL Server). Something like this:
Dim var1, var2 as Integer
Dim Optr as string
var1 = 15
var2 = 25
Optr = +
MyResult(var1, var2, Optr)
And MyResult should equal 40. How can I do this?
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Apr 16, 2010
[code]How do I use variables in a SQL statement?
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Sep 7, 2010
we currently use our own 3rd party customer management system that is cloud-based. They offer pretty good reports; however, we need special reports and the only way to do this is to download our database though web services that the vendor offers. I have some education and experience with programming, but it has been a while. Instead of having to actively engage the webservices directly, our vendor has offered a stepping stone. They have a command line exe that interacts with the webservices and, with the use of different parameters, gets us to the point of having all the data downloaded in xml, csv, or screen printed - the only problem is that it will only do this a table at a time and there are 43 tables I need to interact with. I need to build something that can either be a console application or something that can be run automatically in the middle of the night when there is no load on the server.
Here is what I need to happen:
The command is CMSDownload.exe. It needs to login (again, there are already parameters set up to do this so I can hard code that into the script) Once logged in, the script needs to check a parameter that has been saved that signifies the last date of successful completion. (Obviously, it needs somewhere in the code to place this parameter also). As I mentioned before, each table needs to be downloaded into its own xml file individually. For instance, the following is one example of a table being downloaded in this fashion:
Generate an XML file of all of the data in the accounts table between '01/15/2009 09:13:34 AM' and 01/16/2009.CMSDownload -d somedn -u someusername -p somepassword -f c: empaccounts.xml -m xml -o all -t accounts -s 'start date' -e 'end date'
-d is a login component (credentials)
-u is a login component (username)
[Code]....
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Mar 23, 2012
have a table with following fields
Emp_id varchar(50)
Emp_Name varchar(50)
Emp_surname varchar(50)
[code].....
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Apr 2, 2009
I need to use a SELECT statement to select all data under a column name (like all employee names) and then to add the values to a listbox.
I usderstand that the select statement must be:
"SELECT * FROM EmployeeTable WHERE EmployeeNames LIKE *" (at least I think)
but then what? combobox1.fill ("EmployeesTable") ?
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Sep 14, 2010
How 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
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Aug 20, 2010
I have a simple table in an access database that I'm using in a VS2010 project. I have a combobox control that a user can select the horse power of a motor. I then take that selected value from the control and copy it to a string variable called gstrSelectedHP. All I want to do is run a query that will pull up the full load amps of that horse power motor from the table. I have the query already, but I need to somehow put the gstrSelectedHP in the WHERE part of the query so that it only returns that value.
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Apr 16, 2010
I got this in my SQL statement. I "BOLDED" the problem.SELECT OrderID, CustomerID, EmployeeID, OrderDate, RequiredDate, ShippedDate, ShipVia, Freight, ShipName, ShipAddressShipCity, ShipRegion, ShipPostalCode, ShipCountry FROM Orders WHERE CustomerID =@CustomerID
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Apr 16, 2010
I got this in my SQL statement. I "BOLDED" the problem.
SELECT OrderID, CustomerID, EmployeeID, OrderDate, RequiredDate, ShippedDate, ShipVia, Freight, ShipName, ShipAddress, ShipCity, ShipRegion, ShipPostalCode, ShipCountry FROM Orders
[code]......
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Jun 4, 2012
I have a case statement which compares data by getting parameter such as "eq,ne,gt,..." and so on. Actually this method will filter data by getting filter parameter and filter value. How can I refactor below code?
[Code]...
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Apr 11, 2011
with the following code example:
T04Command04 = New SqlCeCommand("Update GameResults Set CN01=@T04Var02 Where Counter=@T04Var03", T04Database01)
T04Command04.Parameters.AddWithValue("@T04Var02", T04N01)
T04Command03.Parameters.Add("@T04Var03", T04ClnRec01)
T04Command04.ExecuteNonQuery()
I am trying to use two different variables in this SqlCeCommand series, to (1) update only a particular record in the database (2) with a particular variable value. However, I get the following error:
"An SqlCeParameter with ParameterName 't04var03' is not contained by this SqlCeParameterCollection."
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Mar 14, 2011
I 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)?
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Feb 24, 2012
UPDATE: Groo's answer was marked correct as it would be a good alternative. I decided to stick with the select/switch statements to avoid the performance issues of using reflection. As far as I can tell there is no way to do what I want without using Dynamic LINQ (and reflection) or a decompiler (to manually code each LINQ statement, which I am already doing by hand). Note: to make this update DropDownList16 through DropDownList20 were removed (needed the characters).Is there a way to abstract the building of a dynamic Linq to SQL query?
I am trying to build a Linq to SQL query with a dynamic where clause, based on user supplied filters. The user needs to be able to filter strings, integers, and dates using advanced options (equal, not equal, contains, starts with, etc). The user needs to be able to use these filters with as many or few columns as desired.
[Code]...
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Jan 5, 2010
Dim query=Form f in BBSDb.Forms order by f.FormID Descending Select f where I want the f.FormID to be able to replace with a variable..What I mean is.. it doesn't have to f.FormID .. I may want to set f.FormName to be in descending for example using the code dynamically.. Is there anyway to achive?
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Mar 16, 2011
I 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
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Oct 17, 2011
This is an extension of my last question which was answered, so I am starting a new thread. I have a query in LINQ that I was given to trim down the columns of a datatable. This works well, however, I need to make the LINQ query dynamic. So the query below:
Dim qColumnsIWant = From row As DataRow In inDT.AsEnumerable() _
Select _
EPN = row.Field(Of Integer)("EPNID"), _
EPNID = row.Field(Of String)("EPNNumber"), _
Ingot = row.Field(Of String)("Ingot"), _
ShopOrder = row.Field(Of String)("ShopOrder")
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Apr 8, 2012
I have a table which contains a list of products for a company. They input data about how much stock they have and also the level at which they want to be reminded that they need to order new stock.
[Code]...
I want to list all the true results in a form which the user is then able to navigate through. What would be the best way to go about doing this?
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