vb.net, .NET 4.0, sql server 2008 backend.
I have a webpage which contains 3 formviews, each within their own Panel. As the user traverses the page, depending on which step they're on, a certain formview will be visible. After the process is complete, the user will click the Submit button and The button onclick event calls each FormView.Insert statement. Each Formview inserts into a separate table. The issue is that if the last FormView.Insert throws an exception, the first 2 Inserts have already been executed successfully.
My question is, and I hope this isn't too vague but...What is my best option at this stage?
1. Create a single Stored Procedure to handle each Insert in order to handle if one of the Inserts throw an error?
Thank you.
Related
I have a curious problem with an ASP.NET user-control which is dynamically created in VB.NET. Sorry that this is a long post, but I think it’s better for me to explain carefully what I’m doing and what the problem is.
Essentially, the user-control is an HTML table used to display data from a back-end SQL Server DB. It uses a stored procedure to return a DataTable, from which it builds html rows and columns with the values stored in the InnerHtml property of the relevant table cell. This is just a passive display of the data and works perfectly.
However, the user-control also has the facility to insert a new record, triggered by an ASP button. This causes the following sequence of events;
Post-back
The user-control_Init event rebuilds all the existing rows in the table and inserts their values as described above.
The page_Init event.
The page_Load event.
The user-control_Load event.
The button_Click event then builds a new row with the same structure as the main table. But this time it inserts into each table cell a relevant ASP.NET control, such as a textbox or checkbox, holding “null” values. Each control has its ID set explicitly to a unique value. Finally, an “insert flag” is set to true.
The user then enters the data into these controls and clicks an Insert-Save button. This causes another post-back, which follows the procedure described above, except that the “insert flag” tells the user-control_Init event (2) to rebuild the insert row. Then, before the page_Load event (4) the values previously entered by the user are reinstated in the ASP.NET controls from ViewState. Finally, the Insert-Save_Click event calls a stored procedure to save these data to the DB.
All this work perfectly when there are existing rows in the html table. But – and this is the strange behaviour – it fails when there are no existing rows. The first post-back completes successfully although, obviously, event 2 skips over the rebuilding of the existing rows because there are none. However, the insert row is rebuilt correctly and the user can then enter data into the ASP.NET controls. During the second post-back (Insert-Save), the first three events described above work perfectly. But, the moment the code hits the page_Load event (4), all the ASP.NET controls disappear. The html row and cells are still present, including the literal control (index 0) in each cell. No error is thrown at this stage, but when the Insert-Save_Click event occurs and the data should be read from the ASP.NET controls – they are not available and an "index out-of-bounds" error is thrown, because the ASP.NET controls should each have an index of 1 within their cells.
I’ve spent hours (days!) debugging this and I cannot see what is causing these controls to just evaporate! Any clever programmers out there got any ideas please?
I'm having an issue binding the value of a page item to a declared variable in an anonymous PL/SQL block process.
The problem is that the page item (:P4550_REQUESTOR) is not populated with a value until a conditional is met. It appears that the PL/SQL block process is binding the variable to an empty value as soon as the page is loaded, despite the fact that the process does not fire until a specific button has been clicked.
Here is my code:
DECLARE
v_email_to app_user.email%type;
v_requestor VARCHAR2(15);
BEGIN
v_requestor := :P4550_REQUESTOR;
BEGIN
SELECT email INTO v_email_to
FROM app_user
WHERE userid = v_requestor;
END;
SEND_APEX_MAIL (
v_email_to,
'Your vacancy request has been rejected.'
|| chr(10)
|| 'Emailed to: ' || v_email_to
|| chr(10)
|| 'Requestor: ' || v_requestor,
'Vacancy Request Rejected'
);
END;
Does anyone have any thoughts on this?
The block works just fine if I hard code a value to v_requestor. If I try to get the value of P4550_REQUESTOR after the page has loaded, it is empty. After clicking the edit button, P4550_REQUESTOR is populated.
** **MORE DETAIL** **
P4550_REQUESTOR is a page item that resides within the Vacancy Request region which is only displayed when a conditional is met. Specifically, the conditional is an edit button associated with a table row that is created on page load. Clicking the edit button causes the details region to display, and the associated page items to be populated.
The page item values in the Vacancy Request region are populated via an Automated Row Fetch which fires After Header.
P4550_REQUESTOR has a Source Type of DB Column.
The process that fires the code above is set to fire On Submit - After Computations and Validations
If I log the value of P4550_REQUESTOR when the page loads, it shows null. If I log the value after clicking the edit button, I get the expected string value.
Process Flow Control in Oracle APEX
(This is actually useful to think about in other programming disciplines and environments.)
Problem Defined
The problem is that the page item (:P4550_REQUESTOR) is not populated with a value until a conditional is met. It appears that the PL/SQL block process is binding the variable to an empty value as soon as the page is loaded, despite the fact that the process does not fire until a specific button has been clicked.
The problem statement reworded in Apex terminology and presented in the form of an actual question:
There is a REPORT REGION on the page which contains the result of a direct reference to a data table/view. This report is managed by an Apex process called "Automated Fetch" and is initiated automatically by the loading of the page headers.
There is a FORM ITEM on a page which which is populated conditionally by a BUTTON ITEM selection made by the user. The BUTTON ITEM is part of the report results.
There are multiple button items. Each is associated with a value for each report record.
If the user does not select the BUTTON ITEM from the REPORT REGION, the FORM ITEM remains unassigned and contains a "null" value.
There is a defined PL/SQL block of code which is set to execute when a SUBMIT BUTTON item is pressed (also on the same page). Why does my code block (defined page process) run with a null value when it is triggered without first pressing a BUTTON ITEM from the REPORT REGION first?
Event Driven Program Design for Procedural Programmers
The answer is not obvious if you think under the paradigm of a procedural language. Without diving into a lecture on the topic, here's a visual layout of the problem space of the OP that I cooked up to illustrate how the problem can be made more obvious:
This is my Apex page design in implementation. It's generic enough to use as a template for other Apex designs. There are no flow arrows on this diagram because it's a stateful system. One thing causes another thing to happen and so on... but not always and not all at the same time.
Use Cases for Apex UI Page Designs
Try walking through a few use cases to understand how the elements broken down in the diagram operate together. Each user may take any number of click combinations and interactions, but there is a commonality:
They all enter the same initialized conditions on page load.
They all leave the page by: navigating elsewhere or through the SUBMIT button event.
Use Case #1
User chooses {MyPage:SQLReport:ThisButton} from one of the records in {MyPage:SQLReport}
According to {MyPage:SQLReport:ThisButton} #3, the value associated between the report record and the button item is passed to: {MyPage:HTML-Region:ThisItem}
The form item state has been updated and changed from the initial null value.
User selects {MyPage:HTML-Region:ThisSubmit} button to inform the system to continue on.
The submit button executes the defined PL/SQL procedure block: {MyPage:RunCodeBlock}
Use Case #2
User enters page and reviews results displayed in the {MyPage:SQLReport} region.
User decides no additional input is necessary and then selects the {MyPage:HTML-Region:ThisSubmit} button to inform the system to continue on.
(a note: the state of form item {MyPage:HTML-Region:ThisItem} has not been changed from the initial null value at this point... after the submit button has been selected)
The submit button executes the defined PL/SQL procedure block: {MyPage:RunCodeBlock}
Use Case #3
User chooses {MyPage:SQLReport:ThisButton} from one of the records in {MyPage:SQLReport}
According to {MyPage:SQLReport:ThisButton} #3, the value associated between the report record and the button item is passed to: {MyPage:HTML-Region:ThisItem}
The form item state has been updated and changed from the initial null value.
User chooses {MyPage:SQLReport:ThisButton} from a different selection from one of the records in {MyPage:SQLReport}.
According to {MyPage:SQLReport:ThisButton} #3, the value associated between the report record and the button item is passed to: {MyPage:HTML-Region:ThisItem}
The form item state has been updated and changed from the initial value stored in step (2).
User selects {MyPage:HTML-Region:ThisSubmit} button to inform the system to continue on.
The submit button executes the defined PL/SQL procedure block: {MyPage:RunCodeBlock}
The difference between each case should illustrate why the dependent value (ThisItem, or more specifically, page item P4550_REQUESTOR) is null in one use case vs. the other.
Building a Physical Implementation (An Apex Page)
The table I used is called STAR_EMPS. It is similar to the EMP table but has only three columns: ename, deptno and salary. Although it is not super important, this is the data set I used to populate STAR_EMPS:
I used a simple two-column table named STAR_EMPS_LOG for capturing the output of a successfully executed procedure call. You could accomplish the same with just one column, but I wanted a sequential id for tracking the order each event was recorded- for running multiple test cases. The procedure is one of several defined processes kept on this page:
contained in: {MyPage:RunCodeBlock} is below:
DECLARE
-- output from this procedure will be recorded in the star_emps_log
-- table. {MyPage:RunCodeBlock}
mycelebrity star_emps.ename%TYPE:= :P17_CELEBRITY_NAME;
mylogmessage star_emps_log.log_message%TYPE;
BEGIN
-- Conditional; changes message based on the value set for the
-- page item.
if mycelebrity is null then
mylogmessage:= 'No button was pressed on the previous page.';
else
mylogmessage:= 'The user selected: ' || mycelebrity ||
' from the report list.';
end if;
-- populate value from the page item.
INSERT INTO star_emps_log (log_message)
VALUES (mylogmessage);
commit;
END;
This is how the page layout was set up:
As in your example, I made a {MyPage:SQLReport} region with its supporting elements. The SQL Report represents a query directed at the source data table.
{MyPage:Form} has been renamed to {MyPage:HTML-Region}.
{MyPage:SQLReport} is defined by a SQL query, there is also a mock column to use as a place holder for placement of the "edit" buttons.
{MyPage:SQLReport:ThisButton} The button specifications are detailed through this:
The TWO Page processes: PROCESS and BRANCH need to be linked with the same settings referencing a BUTTON triggering Item.
User Interface Test Cases
Run through the three suggested scenarios to get started. Verify that the system is interpreting the requests correctly. This is what the page layout looks like:
The two processes on the system have a definition that wasn't mentioned in previous discussions may solve our original problem at hand:
Some Parting Thoughts
It is a good thing this turns out to be a trivial case once broken down. The diagramming method described here should scale to other Apex applications of varying complexity. There is considerable utility in stepping away from the code, locking down on terminology and trying to describe systems and processes without actual code. Please be sure to share any stories if this approach helps with your own Oracle Apex design challenges.
Onward!
The original, verbose answer seems to way overcomplicate the issue. The session state concepts manual covers this behaviour more succinctly.
Should P4550_REQUESTOR be a normal item created from a wizard, using :P4550_REQUESTOR will return a value in processes running post submit because the submit processes moves values in browser to session state.
If P4550_REQUESTOR is rendered conditionally, then it will always be null and I'm not sure what would happen if you tried to set it - probably depends how.
On a similar note, if you used &P4550_REQUESTOR. to parameterise the process, you would face the behaviour originally described (and made the code less secure)
[Thanks to Filburt and Devjosh. I have restructured the post and included my attempt approach. ]
I have a table on my SQL DB call ReportList which is a list of report. I need to go through that list and interrogate the reportserver, eport by report, to populate a table called ReportParameters. The ReportParameters table has a column for ReportOwnerID which needs to contains the ReportID value of the corresponding (owner) report as listed in the ReportList table.
This is in VB.NET 2005 ASP2.0 and I have ended up with a mess. Please help me with the cleanest approach to doing this.
It needs to work so:- I have a listbox of the reports as per REportList and a GridView that list all the parameters (uniquely - most of the parameters are common to many reports) the idea being that the parameters get set once and the report can be kicked off by selecting them in the ReportList CheckListBox and clicking on Execute.
I would like it that as I click on a particular report in the ListView, the relevant parameters in the Gridview get a green background and those that do not apply are red. The leftmost column in the gridview contains tha Parameter NAME (not editable) and the next column must be editable to populate the value.
DONE SO FAR:
I have tried on clicking the EXECUTE button , to build a parameters string in a testbox and call that with the Javascript OpenReportWin() function when I open the report in a new window. This works fine, but my biggest issue it interrogating the reportserver reports to get back a list of parameters and dooping them into a table. I have triend to use a hidden DataGrid bound to a ds onto the reportParamaters table; I have tried to poulate it using a datalist but I cannot get the hang of these thionsg and its looking messy. Ther must be a simple clean way of gettting the .GetParameters resultset back from the report server and populating the table without having to create a reportviewer object and cycling through the list of reports - it then has to render each report before you can get that list out.
Thanks
I will withdraw this for now. I will submit a solution when I am comfortable that I have reahced a clean solution.
Mac
PLEASE CLOSE!!!
I have a .aspx search screen that displays the results of the search in an asp:GridView component. There can be up to approx 1000 records returned by the search. I want to implememt paging on the grid so that only 15 records are displayed at any one time and the user can page through the results.
I am retrieving the records by passing search parameters to a WCF service which returns a List of particular entity objects. I create a Datatable and insert one DataRow per entity object from the List. I then bind the grid view to the Datatable.
This is how my grid is defined in the .aspx page:
<asp:GridView ID="gridCat" runat="server" AutoGenerateColumns="False" DataKeyNames="CatalogueID"
HeaderStyle-CssClass="fieldHeading" RowStyle-CssClass="fieldContent"
AlternatingRowStyle-CssClass="alternateFieldContent" Width="100%"
AllowPaging="True" AllowSorting="True" AutoGenerateDeleteButton="True"
PageSize="15">
and I also have this method in the code behind (.aspx.vb file):
Sub GridPagingAction(ByVal sender As Object, ByVal e As GridViewPageEventArgs) Handles gridCat.PageIndexChanging
gridCat.PageIndex = e.NewPageIndex
gridCat.DataBind()
gridCat.Visible = True
End Sub
My problem is this: the first page is rendered correctly i.e. the first 15 records are displayed correctly. However, when I navigate to page 2 in the grid, the GridPagingAction method is hit on the server but nothing is displayed in the grid - it is just blank.
I think the reason this is happening is because the Datatable no longer exists on the server when the request for the second page hits the server - is that right? And the asp:GridView, when it is rendering the first page of results, only takes the first 15 records from the Datatble and sends them back to the browser. So when the request for the second page comes in the other records (i.e. records 16 - 1000) don't exist anywhere - is all that correct?
If so, what's the best solution - I can't see how to implement paging without having to do one of the following:
re-perform the search each time the user uses the paging option;
saving the search results on the Session after the first Search retrieving them each time the user uses the paging option;
manually inserting the Search results into ViewState and retrieving them each time the user uses the paging option.
Is there a better way to do this (or am I doing it wrong)? If not, which of the 3 options do you think is the best? I'm leaning towards option 2 as I don't think option 1 is performant and I don't want to be sending loads of unnecessary data back to the browser as per option 3.
All you said is correct. You could either use ViewState or the Session to keep hold of the data on client- or server-side, but if you really have that many records, it might be a good idea to only collect the data you actually need.
So if you want to show records 1 to 10, you perform a query against the database and only fetch those ten records. If you want to show the next ten, you perform another query with the according parameters.
This will improve your performance and memory usage significantly, IF calling your DB is not overly expensive.
This article might give you a start on how to do this:
http://dotnetslackers.com/articles/gridview/Optimized-Paging-and-Sorting-in-ASP-NET-GridView.aspx
If you want an easy solution without any additional efforts, I would query all the records on each postback (your option #1).
If you want the best performing solution with not much overhead, use the custom paging.
I have a simple asp.net web forms page that does an insert to my sql server db. My server was running slow at the time and I pressed Insert button several times because I didn't think it took but it did all 3 times.
So I have duplicates from that one interaction. How would I prevent this?
Thanks,
rod.
Bind the onClick of your button to a javascript and disable or hide the button and optionally display a message like "Please Wait.." to avoid multiple clicks
Code Behind:
Button.Attributes.Add("onclick", "fn_OkClick();");
ASPX file:
<script language="javascript" type="text/javascript">
function fn_OkClick()
{
var okieButton = document.getElementById('<%=Button.ClientID%>');
okieButton.style.display = 'none';
}
</script>
I'd first evaluate if the business rule is correct. Are you sure you shouldn't be able to insert multiple records with those same details? Generally I would think there would be some validation around whether or not something can be inserted. If you can do a blind insert then it suggests you should be able to do multiple inserts of the same data.
Take a resource booking program. For a given resource, at a given time, it can only be booked once. Therefore you would want to prevent people doing what you've done and inserting multiple records into the booking table for the same item at the same time.
As such there should be some validation before you try to insert the record to ensure that the selected resource is in fact available at the time you've selected. If so, insert the record, if not, don't insert the record, and return a meaningful reason to the user as to why.
If there is no validation, then there should be no reason to prevent the user from inserting multiple records.