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Load More Items at End of ListView in Xamarin.Forms [closed]

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I am trying to add more items to at the End of The listview when scrolling, and while doing my research I found this link https://montemagno.com/load-more-items-at-end-of-listview-in/, But when I tried to apply it on my code, I got stuck. I just want to know if someone can help with this. thank you in advance

In my precise I also tried to use this listview that James Montemagno made available, but I did not succeed as well.
I then left for another listview with infinite scroll and it's working for me to this day.
https://github.com/CarlosHSantos/XamarinMarvelApp

I think there might be serveral Issues with your code:
You want your listViewJson.ItemsSource to be a ObservableCollection instead of a normal list. (I assume that it is a normal List, it is not obvious from the code your show)
You maybe want to implement the ItemAppearing in the following way:
ItemAppearing += async (sender, e) =>
if (isLoading || jokeDisplay.value.Count == 0)
return;
//hit bottom!
if (e.Item.ToString() == Items[Items.Count - 1])
{
await LoadItems();
}
};
Lastly, within LoadItems() function, you need to replace Items with
(listViewJson.ItemsSource as ObservableCollection<TypeOfTheItemHere>).Add(ItemToAddHere)
It would be easier if you would have a property within your JokeList class that holds the ObservableCollection, so that you don't have to do all the casting everytime you want to access it.

How do I make background code? [closed]

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I want to make background code that checks if someone hit "H","D", or other letters. Like This,(I mean a background code that is checking this.)
if(e.KeyCode == Keys.U)
{
code;
}

In WinForms you can override onKeyDown() like so:
protected override void onKeyDown(KeyEventArgs e)
{
if (e.KeyCode == Keys.YourKey)
{
// Do something
}
}
Where you substitute YourKey with desired key from Keyboard. (You can use intellisense to see all available options)

Check if any form fields have changed upon saving asp.net c# [closed]

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I've got a large .net form with hundreds of input fields, sometimes users navigate off the form page without saving, what's the best way to check if a field value has changed when they try to navigate away? some c# function or javascript?

Don't take the control out of the users hand :-)
Ask him on exit, if he wants to save the changes. Maybe he did some changes by mistake, which you don't want to save.
You can achieve this by Javascript/Jquery. Something like:
$(document).ready(function() {
formmodified=0;
$('form *').change(function(){
formmodified=1;
});
window.onbeforeunload = confirmExit;
function confirmExit() {
if (formmodified == 1) {
return "New information not saved. Do you wish to leave the page?";
}
}
$("input[name='commit']").click(function() {
formmodified = 0;
});
});

How to allow only valid values in a combobox? [closed]

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in C# with DotNet 4 i have a form with a combobox which is filled with values when starting the program.
Now user can dropdown and select one of the values.
But: It is also possible to write something new into the combobox-field.
Question: What can i do that it is NOT possible to write something which is not part of the list?
Thanks

To make the text portion of a ComboBox non-editable, set the DropDownStyle property to "DropDownList".

It can be done by simply assigning a property to combobox .DropDownStyle = ComboBoxStyle.DropDownList. but, this property do not allow to edit text. means you have to select item either by mouse or by up/down arrow key. You cannot filter result by selecting this property. if you wish to filter result but don't allow to accept invalid value then you can do this by writing some code in cmb_Validating event
private void cmb_Validating(object sender, CancelEventArgs e)
{
if (cmb.SelectedValue == null && cmb.Text != string.Empty)
e.Cancel=true;
}

How to throttle C# workload? [closed]

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I'm working with a file watcher. It only needs to perform the action after no more events have fires for like 10 seconds.
For these types of problems I use a throttle function in JavaScript and I was wondering if C# can do something similar:
var t = null;
function throttleAction(fn){
if(t != null){
window.clearTimeout(t);
}
t = window.setTimeout(function(){
t = null;
fn();
}, 10000);
}
How would I implement something like this in C#?

Use System.Timers.Timer. Set the Interval property to your chosen interval, write your worker function and then pass it as a delegate to the Elapsed event. Finally, Start the timer.