I am writing a program in VB.Net to manage text messages sent through an API. It allows you to view messages in a datagridview and filter by date, sent/unsent etc...
To load the messages I'm executing an SQL statement and retrieving a DataTable which then gets set as the DataSource for my DataGridView control.
The problem is that depending on the filters selected the user could be selecting a lot of records and it would take some time for the DataSource to update. I want to inform the user of this load time by providing a progress bar or label of some kind.
I have used progress bars before when looping through data but this is loading it all at once. I thought of displaying a label when the user clicks to load the data and then hiding it when the data is loaded. But this happens instantaneously even when the data is still loading.
Is there an event on the DataGridView I can use perhaps? Something like .DataSourceLoadStart and .DataSourceLoadFinished.
I know I'm just making those events up... but hopefully it makes it clearer as to what I want.
You could set the label to be visible when load is clicked and try the: DataGridView.DataBindingComplete Event to hide it, this event gets called when the binding is complete.
MSDN Link - DataBindingComplete
A little off topic but... I wonder if you could attach a AJAX update panel with activity/loading image to a gridview? I don't think I've ever seen it done but here's a great application for it.
Related
I have my form with a menu bar and space underneath to display my controls. One of the buttons in my menu bar is suppose to be a print button that prints a graph that's currently in a User Control I display in the form. If the graph was on the form in the print button's eventhandler I could just simply call
graph.printing.print(true)
which isn't going to work in my case since the graph is in the control and not the form.
How do I communicate with a User Control from the containing form and access or pass its variables when needed? I also have a status bar on the bottom of the form which would also need to get updated from the User Control, but I'll be able to deal with that if I got help with just this one part. Please bear in mind, I also have another User Control I'm going to add to the form which will also contain a graph which will need the same treatment as the other graph on the first control when the print button is pressed. I plan on swapping these two out so I have one form displaying one control at a time.
I got this idea from this answer: https://stackoverflow.com/a/18191630/2567273 but after further research I can't find anyone asking about the actual communication process between a form and the control it contains.
I think this answer is close to what I'm looking for, but I think it's leading me down the path to using panels instead of User Controls.
After typing this I noticed the closest answer to my question may be this, but that question has the child raising events and the parent responding while I have the parent raising the event and the parent has to get information from the child.
One way to think about this is Roles. Presumably you built this UserControl to handle the management of the data related to the graphs. As such you can think of them in the Role of a Graphs Specialist . Once you do that, printing them is actually just one more thing it should perhaps do.
The form on the other hand, is not special just because it happens to get receive the command from the user to print. Its role in this might simply to be to know which usercontrol to contact and which method to invoke:
Sub PrintGraphMenuClick....
Select Case something ' determinant as to which UC to contact
Case operation.Foo
ucFoo.PrintGraph
Case operation.Bar
ucBar.PrintGraph
Other menu options like Clear, NewGraph, Save and whatever else there is somewhat the same way. The Form's Role here may be to receive the command from the user and pass it along to the right control, invoking the correct right method and passing the correct parameters - that is not a trivial task.
Of course, rather than a MainMenu, the usercontols could alternatively implement a ContextMenu and even receive those commands directly.
Very often offloading an operation to something else results in so many properties, filenames, streams etc having to be moved from here to there that it becomes burdensome. In this case it is not like the MainForm has some special ability regarding printers that the UserControl cannot handle.
There is only one right solution:
1) Add an event to your user control.
2) Raise the event when the particular "thing" happens in the user control.
3) Attach a handler to the event in Form code.
4) Add code to update the bottom bar in the event handler.
I used the data sources tab to drag and drop some fields from my database onto a form. This created the reqired textboxes/fields/designer components and also created a fill command by default, which is expected.
On my form load event, the following command takes place:
Me.TblQueueTableAdapter.dt_FillIncompleteCases(Me.BE_DataSet.tblQueue)
This command can take a while to fill on the end user's PC. I would like to display something in the meantime while the data is being retrieved so I added a new borderless form which will show before the fill event, then hide after completion.
So the problem as it stands is the main thread is being blocked due to the database fill code above, and my main thread will not display the borderless form. The process of showing and hiding works, but because the thread is blocked, the content of the borderless form is blank. I need to stop the main thread from blocking.
I know I can probably use a background worker to get this data out of the database. I could instantiate a new table adapter and use the fill command in the do work event. If I do this, I canpass back the datatable through e.result but I dont know how to set the datatable to my designer controls. How do I do this?
In the run worker completed event, I imagined something like:
Me.BE_DataSet.tblQueueDataTable = e.result
But this is a type and cannot be set in this way. What do I need to do?
I am trying to create a wrapper to replace the sheridan datagrid actvex control with a datagridview.
The sheridan datagrid control supports an event which fires just before the user is going to add a row to the grid called BeforeInsert.
Does anyone know of an equivalent event in the datagridview control or or some other code I could write which produces the same effect?
I'm having a look at all the events here, I don't see one for Adding or Inserting a row, just Added. Although there's one for Deleting and Deleted strangely enough. I won't pretend to know why. To your question, how exactly will users be adding rows? You could try playing around with the "AllowUserToAddRowsChanged" event and change that property programatically when the user wants to add a row.
I'm writing an intranet ASP.NET page using VB.NET. I've run into a particularly nasty problem dealing with handling file uploads. I'll do my best to explain the problem, and perhaps someone can help.
My problem is almost a duplicate of this one, or this one, except (other than the filename) I don't care about sending the file to the server until the other data has been reviewed.
Here's the situation:
Joe Q. Dataentry inputs some data into several fields. The first 3 are drop down, and when he changes the selection, a postback event is fired that queries a database for valid entries for the other drop down selections. After selecting the values, he inputs some other data, chooses a file to accompany the data and clicks the "Update" button. When he hits the button, it fires a postback event that sends the current data to the server to be validated. The data will create a change in the database, so he is presented with a view of the current state, and what it will look like when his changes are made. He can now either confirm or cancel the operation for whatever reason.
Part of the data he will see involves the extension of the file which may be a PDF, or could also be some image file or other document.
Now here's where my problem is - on each postback event, the fileupload dialog is cleared. I was getting around it by creating a temporary file on the first postback and then renaming if he clicks OK or deleting on Cancel... but I need to do a variety of things, based on the previous state of data and the filename. I've tried to keep some session variables to retain the filename, and that works OK for just renaming the file, but for what I need to do it gets unwieldy.
What I want to do is be able to have the postback event to present the changes, and then when the user clicks "OK", submit the file. Is there any possible way to do that?
One of my thoughts was to do some of the validation client-side (I'm already re-validating server side so I'm not too worried about data security there), but I don't know how I could get the information from the database query.
Thanks for any help, and reading my slightly convoluted story/situation!
EDIT:
It appears that what I want to do is prevent a certain button from firing a full postback. Is there any way to do that?
EDIT II:
I have an update panel on the page already - is there any way for the button to only post what's in the update panel?
What you might want to do is place your drop-downs inside of an ASP.NET AJAX UpdatePanel, and keep your file upload control out of that.
Your update panel will do the post backs and allow your validation logic to happen without submitting the file, then when you hit your final "Save" button (which is also outside of your UpdatePanel) the entire form will be submitted back and you can work with your file then.
I am trying to hide specific columns in an Access 2007 split form through code. I need the form to check certain conditions to see whether it needs to display a column or not. I have code in the form's 'Activate' event to hide the column like this:
txtControl.ColumnHidden = True
This code works in the "Open" event, but if I hide the column on Activate, it won't display these changes until I close the form and open it again. I have tried calling the form's refresh, repaint, and requery methods, but this doesn't work. Please help!
Edit: Ideally, I need this event to occur whenever the focus switches to this form.That's why I'm using the Activate event rather than the Open event.
Try setting it in either the form's Current or Load events. You will also probably need to requery the control after setting that property: Me.TextControl.Requery Current is called every time a form's record is changed, the form is repainted or requeried. Load, as its name suggests, is called once, after the form has opened when the form loads its records. These have always been more reliable for me than using Activate, which really has to do with more the focus of the form, not really what you want.
I've had a problem like this before working in Access 2002. I was able to solve the problem with a subform by setting the subform source object equal to itself and then running the requery.
Me.SubForm.SourceObject = Me.SubForm.SourceObject
Me.SubForm.Requery
See if this technique works for your particular situation.