I am trying to sort a LINQ to SQL query based on two fields. The first field is occasionally null which automatically sorts to the top of an ascending query. Is there any way to make the null entries sort to the bottom?
Here is an example:
From x in SampleDataContext.Event _
Order By x.Date, x.Sequence_Number _
Select x.Date, x.Sequence_Number
[code]....
I trying to do from A to B to D and to E.All in ListBox(A to B)I want to sort smallest to largest from top to bottom(Vertical for B1,B2,B3, B4)[code]
View 18 RepliesI 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 have a dictionary collection as bleow:
mydic.addvalue(key1, val1)
mydic.addvalue(key2, val1)
mydic.addvalue(key3, val1)
mydic.addvalue(key4, val2)
mydic.addvalue(key5, val2)
From the above dictionary I want to delete all the entries where value == "val1", so that the result would have only following entry:
mydic.addvalue(key4, val2)
mydic.addvalue(key5, val2)
My VB source code is on VS2008 and targeted for 3.5
I'm using VB .NET and I know that Union normally works ByRef but in VB, Strings are generally processed as if they were primitive datatypes.Consequently, here's the problem:
Sub Main()
Dim firstFile, secondFile As String(), resultingFile As New StringBuilder
firstFile = My.Computer.FileSystem.ReadAllText(My.Computer.FileSystem.SpecialDirectories.Desktop & "1.txt").Split(vbNewLine)
secondFile = My.Computer.FileSystem.ReadAllText(My.Computer.FileSystem.SpecialDirectories.Desktop & "2.txt").Split(vbNewLine)
[Code]...
I have a generic dictonary which is templated in the following manner:
[code...]
If I wanted to omit certain list items against arbitrary keys (that is the items that are in the list contained within the value part of each of the key value pairs making up the dictionary) given some arbitrary condition (lets say omitting list items where a list item contained the string "abc")
I would expect to able to create/project into a new dictionary which would contain entries which contained lists WITHOUT those items whose name contained "abc"
How do I achieve this using a Lambda expression?
I was trying something like this:
[code..]
In this example, an error is raised if either row.FirstName or row.LastName are NULL.
How do I rewrite the Select clause, to convert a DBNull value to a blank string ""?
Dim query = From row As myDataSet.myDataRow in myDataSet.Tables("MyData") _
Select row.FirstName, row.LastName
NOTE: Since the DataSet is strongly-typed. I can use row.isFirstNameNull(), but IIF(row.isFirstNameNull(), "", row.FirstName) will not work since all parameters are referenced.
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
if there is that much of a performance gain in running a LINQ stored procedure versus a LINQ query?
View 1 RepliesI 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]....
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'm trying to sort an array based on a structure but whenever I do this, it basically erases all the data in the entire array.I have verified that the array is populated correctly, it is when using array.sort that everything returns blank.
View 6 RepliesI have a program where you have three entries, CD name, artist, price and it goes into a listbox and .txt file when closing. I have to have a message box if you enter the same CD name. I have a code to open the .txt file and compare strings but I need to change it to compare only the CD name and not all three entries. Is there a way to do my string compare against my listbox without opening the .txt file?? The program loads the listbox from the .txt file when opening. Private Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click' adds CD information to the list box
' declare variables
Dim strName As String
Dim strArtist As String
Dim strPrice As String
[code].....
I have a LINQ Query:
[Code]...
This works great and sorts on L_Name. But I am trying to allow the user to sort the gridview themselves so I am passing in the SortExpression as a string. But I don't know how to incorperate the SortExpression into the LINQ Query. I tried Order By c. & SortExpression but that did not work.
We are doing a query against an in-memory collection of LINQ data objects. The wrinkle is that we are ordering by a column in a related table whose records have not necessarily been loaded yet (deferred loading:)
Dim oPkgProducts = _
From b In oBillPkg.BillProducts _
Where b.Successful.GetValueOrDefault(Common.X_INDETERMINATE) = _
[code]....
How should I use linq to sort my data when my data contain both numbers and letters? For example my current linq
Dim MyQuery = From c In XDoc.Descendants() _
Where c.Attribute(Y) IsNot Nothing And c.Attribute(Str) IsNot Nothing _
Order By Val(c.Attribute(Y).Value), Val(c.Attribute(X).Value) _
Select Str = c.Attribute(Str)
Returns something like the following
13
167
172
231
44
49
Which is not what I would like it to be...
The output should be like the one below:
13
44
49
167
172
231
I need to sort a datatable. I do it with linq this an example
Dim query = From c In dt.AsEnumerable _
Order By c.Field(Of DateTime?)("LastPurchaseDate"), _
c.Field(Of String)("LastName") Descending
Dim dv As DataView = query.AsDataView
But my problem is that i need to sort the fields not by passing the name of the column but the index of that.
How do I add ROW_NUMBER to a LINQ query or Entity? How can I convert this solution to VB.NET?
[Code]...
I'm having trouble porting that last line. I have been unable to locate a VB.NET example. I'm actually not looking for any paging functionality like the example provides, just good old-fashioned Row_Number(Order By X) row index.
I want to set a certain column to true or false automatically based on what value another column has entered. I managed to get this working by myself using the 'SQL Pane' in VB and testing it by using execute sql but I don't know what to do now. I assumed that I could just save it and it would work from there but that's not the case, it dissapears from the SQL Pane if I close the project (even though it worked fine when I ran the project the first time), so where do I put it/what do I do with it in order to get this to work?
View 1 RepliesI've seen many examples in LINQ but i'm not able to reproduce the same result in vb.net.
I have following code: Dim context As New MyModel.Entities()
Dim rnd As New System.Random()Dim gardens As List(Of Tuin) = (From t In context.Gardens Where _
t.Approved = True And _
Not t.Famous = True _
Order By rnd.Next() _
Select t).ToList()
[Code]...
I am trying to work out a LINQ query to pull items from a List, the List contains a child-nested List - which I need to query for an item, then use the resulting item in my final sort of all records returned the query.[code]...
View 1 RepliesI 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've been reading a fair bit about the performance of using LINQ rather than using a for each loop and from what I understand using a LINQ query would be a little bit slower but generally worth it for convenience and expressiveness. However I am a bit confused about how much slower it is if you were to use the results of the query in a for loop.
Let's say that I have a set called 'Locations' and a set of objects called 'Items'. Each 'item' can only belong to one 'location'. I want to link items that are under the same location to each other. If I were to do this using a normal 'For Each' loop it would be something like this:
For Each it as Item in Items
If it.Location.equals(Me.Location)
Me.LinkedItems.Add(it)
End If
Next
However if i was to use LINQ it would instead be this:
For Each it as Item in Items.Where(Function(i) i.Location.equals(Me.Location))
Me.LinkedItems.Add(it)
Next
is the second (LINQ) option going to loop once through the entire 'Items' set to complete the query, then loop through the results to add them to the list, resulting in essentially two loops, or will it do the one loop like the first (For Each) option?
Is it possible to do the following? [code] Basically I have one Load_Gridview function that is called on all postbacks, and rather than creating a bunch of different cases.I want the filters to stack.My actual code has more filters set up (4 or 5 of the).It all compiles ok but when I run and try to execute with active checked, or a department selected I get the following error. [code]
View 4 RepliesI have below XML file
<?
xml version="1.0" encoding="utf-8" ?><
PageFlow>
<
attributegroup name="Search"><
attributes>
[Code]...
I am looking to sum the "Status" field.
Dim _detailRecords As New DataTable
_detailRecords.Columns.Add("y")
_detailRecords.Columns.Add("z")
[Code]....
I'm also wanting to keep this as an IEnumerable of DataRow because I will be creating a datatable from it with
Dim yyyyy As DataTable = query8.CopyToDataTable
I am Fairly new to Linq and I am trying to write a simple query to return the error messages within my xml file.
<?xml version="1.0" encoding="utf-8"?>
<Error xmlns="urn:xxxxx">
The following errors were detected:
[code].....
if I run this under c#
from p in Addresses where p.Address2 == null select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] IS NULL
if I run this under vb.net
from p in Addresses where p.Address2 = nothing select p.AddressID
it generate this query
SELECT [t0].[AddressID]
FROM [dbo].[Address] AS [t0]
WHERE [t0].[Address2] = ''
p.Address2 is a varchar field that accept null value
why vb.net is "wrong" ?
I'm converting the Linq query below from C# to VB.Net. Can you spot my error? The query joins 3 XML datasets. C# - This one works great.
List<Course> courses =
(from course in CourseXML.Descendants(ns + "row")
join coursecategory in CourseCategoryXML.Descendants("Table") on (string)course.Attribute("code") equals (string)coursecategory.Element("DATA")
[code]....
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)?