LINQ Statement Where Result Count Is Used In Expression's Condition?
Mar 23, 2009
I have a requirement where I have to add items into a List(Of T) (let's call it Target) from an IEnumerable(Of T) (let's call it Source) using Target.AddRange() in VB.NET.
The ? part is a tricky condition that is something like: As long as the as yet unenumerated count is not equal to what is needed to fill the list to the minimum required then randomly decide if the current item should be taken, otherwise take the item.Somethig like...
Source.Count() - Index = _minimum_required - _curr_count_of_items_taken _
OrElse GetRandomNumberBetween1And100() <= _probability_this_item_is_taken
' _minimum_required and _probability_this_item_is_taken are constants
The confounding part is that _curr_count_of_items_taken needs to be incremented each time the TakeWhile statement is satisfied. How would I go about doing that? I'm also open to a solution that uses any other LINQ methods (Aggregate, Where, etc.) instead of TakeWhile.If all else fails then I will go back to using a good old for-loop =)
I have added a column to a Datatable called CallsPerDay which is there to tell me how many telephone calls have been made on a particular day or days.Is there a datacolumn.expression which will allow me to Filter on the day, count the rows and then populate this added column with the result.
I have something that I want to do and what looks very simple, but I cannot get it to work. I want to build a function that gets as input a xdocument and some other strings. It should have a return that contains a filtered part of the xdocument in a way that I can use it as input for a new Linq function. This is what I mean:
Private Function fncGetFilteredDecendantsOfNode(ByVal xdocDoc As XDocument, _
Can a LINQ or a LAMBDA expression be used to count the 1's in a binary string ?For example, if I convert a number to its BINARY using.>>
Dim binaryString As String = Convert.ToString( numberVariable, 2 )
1) Without using a loop such as a FOR NEXT loop, can I count the number of 1's in the STRING using LINQ or a LAMBDA expression?
2) Can I get the indexes of where the 1's are at in a collection such as a LIST using LINQ or a LAMBDA expression?I know the syntax of some LINQ expressions, however, I don't know which method may be suitable.
I have a stored procedure that repeats a block of T-SQL statements using WHILE logic until it finds a matching record in a table. When I execute the procedure directly from the SQL Management Studio, it works and returns a record, even when the statements within the WHILE logic have to be repeated over and over again before a matching record is found.
However, when I use the same stored procedure as the commandtext property of an sqlcommand object in Visual Studion 2008 (VB) and call the executereader method of the sqlcommand, the resulting SqlDataReader will only return a row if the T-SQL statements within the WHILE logic find a matching record after a single pass. If it takes more than one pass to find a matching record the SqlDataReader does not return a row. It's like it abandons the execution of the stored procedure after the first pass of the statements within the While logic, disregarding the repetition.
I was convinced that If <expression> Then <statement [:statement]> Else [statements] in concrete form of If a = b Then SayHello() Else SayBye() End has sense. I read article on msdn on If-then-else, but I forgot why I was reading, so I concluded, that snippet above means this
If a = b Then HelloIsSaid : IsNotEnded Else ByeIsSaid : IsEnded But I have tested it now, and I see, that Else without statement is nothing more than decoration. It would be pretty good if it had function I described. Do you think its good request? Or do you know any circumstance where this Else has some function?
method to query. I then use a datarepeater to display the results. Is there a way to programatically tell if no results are returned? I'm aware of the Dataset.tables.Rows.count, but can this be done after the select method?
I am developing a VB.NET ASPX file and am trying to run a string query in VB.NET, but now I get the above error message. How can I determine the cause? Some of the code in this
I think im going mad but can some show me what im missing, it must be some stupidly simple i just cant see the wood for the trees.BOTH side of this if then else statement are being executed?
Ive tried commenting out the true side and moving the condition to a seperate variable with the same result. However if i explicitly set the condition to 1=0 or 1=1 then the if then statement is operating as i would expect. i.e. only executing one side of the equation...
The only time ive seen this sort of thing is when the compiler has crashed and is no longer compiling (without visible indication that its not) but ive restarted studio with the same results, ive cleaned the solution, built and rebuilt with no change?
Dim dset As DataSet = New DataSet If (CboCustomers.SelectedValue IsNot Nothing) AndAlso (CboCustomers.SelectedValue <> "") Then Dim Sql As String = "Select sal.SalesOrderNo As SalesOrder,cus.CustomerName,has.SerialNo,
I need to write an sql statement that has an IF condition in it
This is my current statment:
"SELECT * From History Where DelNoteNum = " & delNote & " ORDER BY StockLoc"
What I need to do though is if the StockLoc > 4000 then group by ProductCode. I definatly only need to do this if the stock location is greater than 4000 though.
i want to make condition statement in my function. i use this method : [code]if i try to insert a data already in the database, the function will directly go to the updateDatabase()the problem is, if i try to insert the data that currently not in the database, the function will directly go to update database as well.
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 a IF statement which is checking each row in the data table (for a match) and ELSE statement with commands which are executed if the If statement is not satisfied. Now I would like to write like so that it goes to the Else part BUT ONLY for values which are not satisfied in the IF statement. If I am more specific; I would like to calculate values if a match is found and just print them if it is not fond (usually there are both cases). Now the problem is the bold text; if there is a match found I don't want it processed BUT if the match is found I do. How can I write that?
currencyPosition = 0 Dim d As Integer = w + 100 For Each currency In Ary
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?
How to update columns in datatable using linq without conditions. I have an idea that I'm just gonna loop all the data in the datatable but don't know what comes in LINQ.
Im trying to get the result of an SQL statement and store it in an integer variable "count" in vb so it can then be displayed on my website showing the user the total Open records:SELECT COUNT (recordID) FROM [tbl_Records] WHERE [Status] = 'Open'
I've been working with my project. I make a quiz and I put check value for every label. If the user is correct the label with shows or else the label is in a hide status. My problem now is how do I count those labels to display his/her result. If there are 3 labels shown in the form in automatically the user got 3 points and that "3" with be put into a textbox...
I'm relatively new to VB. I want to perform a SELECT statement that uses a variable to return a value, example; mysql> SELECT room_description FROM room_descriptions WHERE current_room = 'someVariable'; And display the result in a TextBox i.e. TextBox.text = someVariable. So how do I perform a query from VB that passes a variable? How do I assign the result to a variable?
i have a table with data title and date of the data inserted.and right now i want to do count to make the statistic out of it.can i do multiple count in one sql statement?like from, the column date, i want to count how many on this month, and how many in this year, until month selected. this is what i have come up, for now.
SELECT a.trigger_type_code , c.trigger_name , COUNT(*) AS number FROM issue_trigger a
I want to display an image if 2 conditions are met. The data item is not null. The value of the data item is greater than 0 Markup <img id="Img1" runat="server" visible='<%#IIF( DataBinder.Eval(Container.DataItem, "amount") is DBNull.Value Or DataBinder.Eval(Container.DataItem, "amount") = 0, False, True)%>' src="/Images/check.png" />
Error message: Operator '=' is not defined for type 'DBNull' and type 'Integer'.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.InvalidCastException: Operator '=' is not defined for type 'DBNull' and type 'Integer'.
