I am using checkedListBox with windows forms . I am using LINQ for database operations.
Now when user edits the form I need to see if checkboxes are new selected and if entry does not exist insert to the table.If they had checked it before and now they checked it off I need to delete that entry from database. Can some one help me how can I do this in LINQ some easy way ? In sort I need to Insert any newly selected checkboxes and delete if they existed before but are not checked off.
Thanks a lot.
You can easily get the checked and unchecked items, but to determine if they are originally checked/unchecked, you have to store that somewhere, whether the tag property or in a variable somewhere.
HTH.
Related
I have read all sorts of documents across the web about what should be a farly common and painless implementation. Since I have found no consistent and slick reply (even the Embarcadero website describes some properties wrong!) I am going to post a "short" howto.
Typical, frequent use case: the developer just wants to painlessy show a couple of database-extracted information in a combo box (i.e. a language selection), get the user's choice out of it and that's it.
Requirements:
Delphi, more or less any version. VCL is covered.
A database table. Let's assume a simple table with an id and value fields.
A DataSet (including queries and ClientDataSets).
A DataSource linked to the DataSet.
A TDBLookupComboBox linked to the DataSource that shall show a list of values and "return" the currently selected id.
Firstly, we decide whether the sort order is the one we want or not and if all the items in that table must be shown. Most often, a simple ORDER BY clause or a DataSet index will be enough. In case it's not, we may add a sort_order field and fill it with integers representing our custom sort order. In case we want to show just some items, we add a visible or enabled field and use it in our SQL. Example:
SELECT id, value
FROM my_database_table
WHERE visible = 1
ORDER BY sort_order
I have defined visible as INTEGER and checking it against 1 and not TRUE because many databases (including the most used SQLite) have little support for booleans.
Then an optional but surprisingly often nice idea: temporarily add a TDBGrid on the form, link it to the same TDataSource of the TLookupComboBox and check that you actually see the wanted data populate it. In fact it's easy to typo something in a query (assuming you are using a SQL DataSet) and get no data and then you are left wondering why the TDBLookupComboBox won't fill in.
Once seen the data correctly show up, remove the grid.
Another sensible idea is to use ClientDataSets for these kinds of implementations: due to how they work, they will "cache" the few rows contained in your look ups at program startup and then no further database access (and slowdown and traffic) will be required.
Now open the TDBLookupComboBox properties and fill in only the following ones:
ListSource (and not DataSource): set it to the TDataSource connected to the DataSet you want to show values of.
ListField: set it to the field name that you want the user to see. In our demo's case it'd be the value field.
KeyField: set it to the field name whose value you want the program to return you. In our demo it'd be the id field.
Don't forget to check the TabOrder property, there are still people who love navigating through the controls by pressing the TAB key and nothing is more annoying than seeing the selection hopping around randomly as your ComboBox was placed last on the form despite graphically showing second!
If all you need is to show a form and read the TDBLookupComboBox selected value when the user presses a button, you are pretty much sorted.
All you'll have to do in the button's OnClick event handler will be to read the combo box value with this code:
SelectedId := MyCombo.KeyValue;
Where SelectedId is any variable where to store the returned value and MyCombo of course is the name of your TDBLookupComboBox. Notice how KeyValue will not contain the text the user sees onscreen but the value of the id field we specified in KeyField. So, if our user selected database row was:
id= 5
value= 'MyText'
MyCombo.KeyValue shall contain 5.
But what if you need to dynamically update stuff on the form, depending un the combo box user selection? There's no OnChange event available for our TDBLookupComboBox! Therefore, if you need to dynamically update stuff around basing on the combo box choices, you apparently cannot. You may try the various "OnExit" etc. events but all of them have serious drawbacks or side effects.
One possible solution is to create a new component inheriting from TDBLookupComboBox whose only task is to make public the hidden OnChange event. But that's overkill, isn't it?
There's another way: go to the DataSet your TDBLookupComboBox is tied to (through a DataSource). Open its events and double click on its OnAfterScroll event.
In there you may simulate an OnChange event pretty well.
For the sake of demonstration, add one integer variable and a TEdit box to the form and call them: SelectedId and EditValue.
procedure TMyForm.MyDataSetAfterScroll(DataSet: TDataSet);
var
SelectedId : integer;
begin
SelectedId := MyDataSet.FieldByName('id').AsInteger;
EditValue.Text := MyDataSet.FieldByName('value').AsString;
end;
That's it: you may replace those two demo lines with your own procedure calls and whatever else you might need to dynamically update your form basing on the user's choices in your combo box.
A little warning: using the DataSet OnAfterScroll has one drawback as well: the event is called more often than you'd think. In example, it may be called when the dataset is opened but also be called more than once during records navigation. Therefore your code must deal with being called more frequently than needed.
At this point you might rub your hands and think your job is done!
Not at all! Just create a short demo application implementing all the above and you'll notice it lacks of an important finishing touch: when it starts, the combo box has an annoying "blank" default choice. That is, even if your database holds say 4 choices, the form with show an empty combo box selected value at first.
How to make one of your choices automatically appear "pre-selected" in the combo box as you and your users expect to?
Simple!
Just assign a value to the KeyValue property we already described above.
That is, on the OnFormCreate or other suitable event, just hard-code a choice like in example:
MyCombo.KeyValue := DefaultId;
For example, by using the sample database row posted above, you'd write:
MyCombo.KeyValue := 5;
and the combo box will display: "MyText" as pre-selected option when the user opens its form.
Of course you may prefer more elegant and involved ways to set a default key than hard-coding its default value. In example you might want to show the first alphabetically ordered textual description contained in your database table or whatever other criterium. But the basic mechanic is the one shown above: obtain the key / id value in any manner you want and then assign it to the KeyValue property.
Thank your for reading this HowTo till the end!
Please let me know if you have already worked in wpf based windows application
my query is How to retrieve objects from a WPFGrid control in qtp. when spying, qtp is identifing only the WPFGrid and note the objects inside it. pls suggest workaround for this
WpfWindow("title").WpfTable("title")
Inside the wpftable there are four columns and some rows. first column contains chechboxes. i want to check/uncheck that. anything inside the wpftable are not recognized by object spy
Regards
You want to perform an operation on CheckBoxes , if yes, than you need to
WpfWindow("title").WpfTable("title").WpfCheckBox("index:=0").Click
Spy the check box and check for the property.
I'm working with Oracle ADF and I can not get a simple feature, practically, the value of an input box (from a binding) must be stored on the database in a table other than the original? How do I go about using the ADF? Do you have ideas, example?
maybe create a separate EO/VO for the other table and simply copy the value from one bound field to another? I assume you have a button to commit changes. The backing bean code could copy the values, or use a setActionListener tied to the button to copy the values.
It can be done both programmatically and using adf-bindings. which one do you want?Be specific on what you ask
I'm not sure how to fix this issue, but when I utilize combo boxes on my form which selects data from multiple tables I'm not able to save any of the data selected.
I tried to use the Bound form utility but it only asked me to "Enter Parameter Value". I took out the "Bound" portion of the code and the combo box works fine.
I have a nice little save button, but it doesn't actually save anywhere.
I tried using a query, but that didn't fix it either unless, of course, I didn't do the query correctly.
Here is the "Row Source" information...
SELECT SubArea.SubAreaID, SubArea.SubAreaName, SubArea.ProductName FROM SubArea WHERE (((SubArea.ProductName)=Forms![Combo Form]!Product));
Do I need to put something in VBA or perhaps a Macro to have all the data selected to actually save into a table? HELP!
For the Bound Form
Open the form in design mode, right click on the combo box and go to properties. Check out if it is actually bound to something in the Control Source field.
I have a Microsoft Access form that is bound to a linked SQL Server table that has a computed column. I have a control bound to the computed column.
I already realize that the computed field cannot be refreshed until AFTER a record is saved. Beyond that, what is the best way to refresh that textbox that is bound to the computed column after save.
I would prefer not to do a me.requery (a requery of the whole recordset).
Is there a way to JUST refresh that one field?
EDITED FOR CLARITY: There are actually a few strategies to consider.
Form.Refresh() will refresh your Form's recordsource capturing modifications and deletions to existing records and will stay positioned on the current record. However, you would not see any NEW records that were added since you opened your form.
Form.Requery() will re-run the Form's recordsource query. You will see all the Form.Refresh() changes AND it will show you any new records. On the UI, Form.Requery() repositions to the first record.
Form.Control.Requery() is similar to Form.Refresh() in that you will not change record position or see NEW records. It will update your control, assuming the control is based on a query/table.
You'll need to be sure that the triggering event involves a database update. There can be cases where the control's AfterUpdate() precedes database I/O, which wouldn't help you.
Thanks guys. Here it what worked.
In the Form AfterUpdate event I did a Me.ControlName.Requery. This was perfect as it did not do a complete form refresh or requery.
I just experimented with different event/method combinations until I got the best result.
Thanks for the input.
Seth
2016 (related) Answer: In Access 2016, I have a control that is a calculated field based on values in 4 other bound textboxes. I set the Control Source for the calculated field to be =gsngCalculatePaymentAmount([txtInterestRate],[txtLengthOfLoanInYears],[txtSalePrice],[txtMoneyDown]).
But I needed the value to be refreshed whenever ANY of the values for any of those 4 textboxes changed. Had difficulty in making the calculated value refresh. SOLUTION: In the AfterUpdate event in EACH of the 4 textboxes whose value was being used for the calculated field, I simply did the following:
Dim v1 As Variant
v1 = Me.txtMyCalculatedTextbox
Simply referencing the value of the calculated field resolved it!
Rex
Have you tried .Refresh for either the underlying recordset, or for the bound control? I would expect it to work for a Jet/ACE back end, but the interaction with different database server back ends is going to be non-predictable.
There might also be an interaction with you ODBC refresh interval, but I would expect a manual refresh in code to take care of that.
Where to call it is another issue -- I would assume the appropriate place would be in the AfterUpdate events of the controls bound to the fields the calculation is based on. But you might have to save the record for the server-side calculation to happen -- Refresh alone might or might not do the trick. I know with Jet/ACE data sources a Refresh saves the record, but I don't know for certain if it behaves the same way with ODBC data sources.
I did it this way (the control source of txtTextBox is an SQL Server field whose value is computed):
On Error Goto ErrorHandler
'After saving data when I wanted to see the updated value of computed field
txtTextBox = txtTextBox & ""
ErrorHandler: If err.Number = -2147352567 Then 'The data has been changed.
Resume Next
else
msgbox err.description
end if