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How do we clear previous page data on SelectedIndexChanged Event..? [closed]

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I have aspx page.having an issue is that if we select first time option from drop down value gets appears on the page.but when we select second time option from drop down still previous data getting appears. how do i clear all the previous data after drop-down SelectedIndexChanged Event..?

As you have not provided the code when i'm writing this answer. In Asp.net u can achieve this by using jquery. I'm using club dropdown list with ID clubs as an example. This event will bind to the list and will keep on updating selected variable when the selectedIndex change. Then you can simply pass the selected variable value to lets say a span element with id spanClub
$(document).ready(() => {
$('#Clubs').change(() => {
let selected = $('#Clubs :selected').text();
$('#spanClub').text(selected);
});
});

Updating continuously listview with data from an ObservableCollection<T> [closed]

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I need to bind a list an observablecollection to the listview. This listview must be updated each time when data changes in the observablecollection.
For now I can only bind one element of the observablecollection to the listview at the same time, whenever the second one is bound, it will cover the last one.
My purpose is to bind all the data which are created by calling LoadAlarms() in to the listview .
These are my XAML codes:
my Alarms class
My codes in viewmodel
the fist time LoadAlarms are called, I have the result
The second time LoadAlarms are called,I have the result
I would like to display these both results to the listview but I can only see the last update.

Your class Alarms must be inherited from NotificationObject and its properties must do RaisePropertyChanged whenever they change.
ObservableCollection should be allocated once and then only use add, remove etc.
Why do you have a ListView that contains a grid that contains a grid that contains another ListView? What are you trying to do if I may ask.
Hope this helps..

Each time you call LoadAlarm() you overwrite your observable collection with a new one.
Call AlarmList = new ObservableCollection<Alarms>() only once for example in a constructor.

Form updation based on users choice from combobox [closed]

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I am making an application where the user has to choose a value from a combobox. Based on the users choice the form should be filled with relevant labels and textboxes. How do I achieve this?
One way I think this could be achieved is by creating all labels and textboxes, and based on the users choice hide the irrelevant ones. But this seems to be very cumbersome. Is there any neat way to do it?

Could you just give me leads from where I could pick up the many
ways? #Jumpei – user2276910 8 mins ago
Just you know, everything in the comments was a lead of some kind. Whichever approach you chose, showing/hiding data is essential. Your combobox selection is a private case. Much more frequently, you gonna need/use this to handle user access so there is no way you gonna start building your application and at some point discover that you can't show/hide data or controls. That's just not the case. In fact since each approach will give you that option, to get a concrete answer will require a lot more information about the project itself and the overall architecture than just this one particular form.
Having said that I will suggest you approach which I think is not the best one, but very intuitive and at some point when you feel more confident you change this.
So in order to achieve this create the form setting the default visibility to all elements. Adding/removing controls dynamically is not that trivial but setting the visibility option is pretty straight forward so I think it's better to start by using the visibility option.
When you are ready with the default state of the form you gonna need few methods. First, an event handler for the combobox select which should be something like this:
private void ComboBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
ComboBox comboBox = (ComboBox) sender;
string userSelection = (string)ComboBox1.SelectedItem;
From now on you should make a few things. First check if the userSelection is something valid. This check is essential, after you are sure that this is valid selection you gonna proceed (and we are still in the SelectedIndexChanged event) by calling a a method :
private void SetControlsToDefault()
{
}
This method will contains all your controls with their default visibility status. That's required because when the user make more than one selection with the combobox if we don't hide the once that were shown on the previous selection you will end up with visible controls when they should be hidden for the certain selection.
So once we are sure that the form is returned to it's initial state we need to check what exactly has the user selected and show the relevant controls.
Here some would suggest to use switch I'll suggest if-else if statements since I think this will make it more understandable but you can change it if you like so again in the event handler after calling SetControlsToDefault(); we have this:
if (userSelection.Equals("selection1"))
{
ShowControlsForSelectionOne();
}
else if (userSelection.Equals("selection2"))
{
ShowControlsForSelectionTwo();
}
else if (userSelection.Equals("selection3"))
{
ShowControlsForSelectionThree();
}
where ShowControlsForSelectionOne(), ShowControlsForSelectionTwo(), ShowControlsForSelectionThree() are all private methods where you gonna set the visibility only to those elements relevant to the selection. And that should be all. This is one of the many ways to complete this task.

Is it possible to display a table/a Dictionary collection in the ToolTip of an image? [closed]

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I have a requirement to show a list of details in a ToolTip. Is this possible to do? I tried setting a Dictionary to a Tooltip in the code behind. It just displayed Collection.?? Kindly help

You can display anything you choose in a tooltip (WPF is nice like that - you can template anything). However, when you set a Dictionary to the tooltip value, it doesn't know what you want to do with it and defaults to a useless string of text.
Try setting a template for your tooltip that would render the dictionary in a useful way. Since ToolTip is a ContentControl, it will work this out for itself if there's a suitable template available (either keyed by type, or set within the ToolTip).

Navigation on Main Form [closed]

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I am Creating an app with C#. I have a ListView on the Main Form(FormM) which lists all the record, i can select on record and edit it in the new form(FormC). Now I want to have a Navigator on the Main Form. Suppose that the FormC is open and showing a record for edit. in That case i want that if i click the navigate button on the Main Form, the value on the FormC changes according the next or previous move of navigation.
the Navigation buttons is in the FormC in any samples that i found in internet. but i want those be separated.
any sample or idea is appreciated.

In your FormM, make the listview a static member, to do this, go to FormM.Designer.cs, locate the declaration of listview and change it to public static type from private type. After you do this, plenty of errors will be reported in the same file. To fix those, replace all this.listview with only listview.
The above configuration will make your listview accessible from any other form. To access the listview from FormC, user FormM.listview.
Similarly change the Text box/area from FormC to public static. This will make the textbox accessible from FormM.
When you press next and previous buttons, change the selection controls between items and in the SelectedItemChanged action function, put the code to send the selected item to FormC's text box.
Eg: FormC.textbox1.text = {your code to fetch the selected item}