ASP.Net Core MVC - Bind to List of Strings With Ability To Add/Delete - asp.net-core

Question

I want to bind to list of strings with ability to add new item or delete existing, similar to the UI in Azure DevOps -> Process -> Edit Work Item type... it has an a add text box/button at the top, the list of items, and the ability to delete each item with an X.
I tried to look at the html code but it seems dynamically created with javascript. Any existing solution so i don't need to reinvent the wheel? Thank you

Answer 1

According to your description, when the cursor focuses on the input text element, it will show the select items, and might be it implement the autocomplete function.
To achieve this effect, first, you should use JQuery Ajax to get the selectable items from the controller, then, you could attach the focusin, input and keydown events on the input text element, in these events, you could according to the entered value to add html elements, in order to show/hide the select item.
For the delete icon on each select option, you could use the Font Awesome element, and attach the click event to achieve the delete action.
Finally, to achieve the add new value feature, you could use the Bootstrap Modal to show a popup modal and insert the new value.
More detail steps, you could check the following sample code:
Controller:
//main page
public IActionResult SelectIndex()
{
return View();
}
//this method is used to get the select items.
[HttpGet]
public IActionResult GetSelectItems()
{
//initial data. You could query database and get the real data.
List<string> list = new List<string>() { "Angola", "Anguilla", "Bahamas", "Bahrain", "Bangladesh", "Barbados", "Cambodia", "Cameroon", "Canada", "Dominica", "Dominican Republic", "Ecuador", "Egypt" };
return Json(list);
}
View page (SelectIndex.cshtml):
CSS style:
<style>
* {
box-sizing: border-box;
}
body {
font: 16px Arial;
}
/*the container must be positioned relative:*/
.autocomplete {
position: relative;
display: inline-block;
}
input {
border: 1px solid transparent;
background-color: #f1f1f1;
padding: 10px;
font-size: 16px;
}
input[type=text] {
background-color: #f1f1f1;
width: 100%;
}
input[type=submit] {
background-color: DodgerBlue;
color: #fff;
cursor: pointer;
}
.autocomplete-items {
position: absolute;
border: 1px solid #d4d4d4;
border-bottom: none;
border-top: none;
z-index: 99;
/*position the autocomplete items to be the same width as the container:*/
top: 100%;
left: 0;
right: 0;
}
.autocomplete-items div {
padding: 10px;
cursor: pointer;
background-color: #fff;
border-bottom: 1px solid #d4d4d4;
}
/*when hovering an item:*/
.autocomplete-items div:hover {
background-color: #e9e9e9;
}
/*when navigating through the items using the arrow keys:*/
.autocomplete-active {
background-color: DodgerBlue !important;
color: #ffffff;
}
</style>
main html resource:
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
<!--Make sure the form has the autocomplete function switched off:-->
<form autocomplete="off">
<div class="autocomplete" style="width:300px;">
<input id="myInput" type="text" name="myCountry" placeholder="Country">
</div>
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#myModal">
<i class="fa fa-plus"></i> Add Value
</button>
<!-- The Modal -->
<div class="modal" id="myModal">
<div class="modal-dialog">
<div class="modal-content">
<!-- Modal Header -->
<div class="modal-header">
<h4 class="modal-title">Add a New Value</h4>
<button type="button" class="close" data-dismiss="modal">×</button>
</div>
<!-- Modal body -->
<div class="modal-body">
<input id="inputNewValue" type="text" placeholder="Enter a new Country">
</div>
<!-- Modal footer -->
<div class="modal-footer">
<button type="button" class="btn btn-primary" id="btnAddNew" data-dismiss="modal">Submit</button>
</div>
</div>
</div>
</div>
</form>
JavaScript script:
<script>
function autocomplete(inp, arr) {
/*the autocomplete function takes two arguments,
the text field element and an array of possible autocompleted values:*/
var currentFocus;
/*execute a function when focus on the text field*/
inp.addEventListener("focusin", function () {
var a, b, i, val = this.value;
/*close any already open lists of autocompleted values*/
closeAllLists();
if (!val) { arr = countries.slice(0, 5); }
/*create a DIV element that will contain the items (values):*/
a = document.createElement("DIV");
a.setAttribute("id", this.id + "autocomplete-list");
a.setAttribute("class", "autocomplete-items");
/*append the DIV element as a child of the autocomplete container:*/
this.parentNode.appendChild(a);
/*for each item in the array...*/
for (i = 0; i < arr.length; i++) {
/*check if the item starts with the same letters as the text field value:*/
if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {
/*create a DIV element for each matching element:*/
b = document.createElement("DIV");
/*make the matching letters bold:*/
b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
b.innerHTML += arr[i].substr(val.length);
/*insert a input field that will hold the current array item's value:*/
b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
b.innerHTML += "<span style='font-size: 1em; color: Tomato; float: right'><i class='fa fa-times'></i></span>"
/*execute a function when someone clicks on the item value (DIV element):*/
b.addEventListener("click", function (e) {
/*insert the value for the autocomplete text field:*/
inp.value = this.getElementsByTagName("input")[0].value;
/*close the list of autocompleted values,
(or any other open lists of autocompleted values:*/
closeAllLists();
});
b.getElementsByTagName("span")[0].addEventListener("click", function (e) {
e.stopPropagation();
var deletevalue = this.parentElement.getElementsByTagName("input")[0].value;
//delete item from the data array.
const index = countries.indexOf(deletevalue);
if (index > -1) {
countries.splice(index, 1);
}
//remove item from current
document.getElementsByClassName("autocomplete-items")[0].removeChild(this.parentElement);
//closeAllLists(e.target);
autocomplete(document.getElementById("myInput"), countries.sort());
});
a.appendChild(b);
}
}
});
/*execute a function when someone writes in the text field:*/
inp.addEventListener("input", function (e) {
var a, b, i, val = this.value;
/*close any already open lists of autocompleted values*/
closeAllLists();
if (!val) {return false;}
currentFocus = -1;
/*create a DIV element that will contain the items (values):*/
a = document.createElement("DIV");
a.setAttribute("id", this.id + "autocomplete-list");
a.setAttribute("class", "autocomplete-items");
/*append the DIV element as a child of the autocomplete container:*/
this.parentNode.appendChild(a);
/*for each item in the array...*/
for (i = 0; i < arr.length; i++) {
/*check if the item starts with the same letters as the text field value:*/
if (arr[i].substr(0, val.length).toUpperCase() == val.toUpperCase()) {
/*create a DIV element for each matching element:*/
b = document.createElement("DIV");
/*make the matching letters bold:*/
b.innerHTML = "<strong>" + arr[i].substr(0, val.length) + "</strong>";
b.innerHTML += arr[i].substr(val.length);
/*insert a input field that will hold the current array item's value:*/
b.innerHTML += "<input type='hidden' value='" + arr[i] + "'>";
b.innerHTML += "<span style='font-size: 1em; color: Tomato; float: right'><i class='fa fa-times'></i></span>"
/*execute a function when someone clicks on the item value (DIV element):*/
b.addEventListener("click", function (e) {
/*insert the value for the autocomplete text field:*/
inp.value = this.getElementsByTagName("input")[0].value;
/*close the list of autocompleted values,
(or any other open lists of autocompleted values:*/
closeAllLists();
});
b.getElementsByTagName("span")[0].addEventListener("click", function (e) {
e.stopPropagation();
var deletevalue = this.parentElement.getElementsByTagName("input")[0].value;
//delete item from the data array.
const index = countries.indexOf(deletevalue);
if (index > -1) {
countries.splice(index, 1);
}
//remove item from current
document.getElementsByClassName("autocomplete-items")[0].removeChild(this.parentElement);
//closeAllLists(e.target);
autocomplete(document.getElementById("myInput"), countries.sort());
});
a.appendChild(b);
}
}
});
/*execute a function presses a key on the keyboard:*/
inp.addEventListener("keydown", function (e) {
var x = document.getElementById(this.id + "autocomplete-list");
if (x) x = x.getElementsByTagName("div");
if (e.keyCode == 40) {
/*If the arrow DOWN key is pressed,
increase the currentFocus variable:*/
currentFocus++;
/*and and make the current item more visible:*/
addActive(x);
} else if (e.keyCode == 38) { //up
/*If the arrow UP key is pressed,
decrease the currentFocus variable:*/
currentFocus--;
/*and and make the current item more visible:*/
addActive(x);
} else if (e.keyCode == 13) {
/*If the ENTER key is pressed, prevent the form from being submitted,*/
e.preventDefault();
if (currentFocus > -1) {
/*and simulate a click on the "active" item:*/
if (x) x[currentFocus].click();
}
}
});
function addActive(x) {
/*a function to classify an item as "active":*/
if (!x) return false;
/*start by removing the "active" class on all items:*/
removeActive(x);
if (currentFocus >= x.length) currentFocus = 0;
if (currentFocus < 0) currentFocus = (x.length - 1);
/*add class "autocomplete-active":*/
x[currentFocus].classList.add("autocomplete-active");
}
function removeActive(x) {
/*a function to remove the "active" class from all autocomplete items:*/
for (var i = 0; i < x.length; i++) {
x[i].classList.remove("autocomplete-active");
}
}
function closeAllLists(elmnt) {
/*close all autocomplete lists in the document,
except the one passed as an argument:*/
var x = document.getElementsByClassName("autocomplete-items");
for (var i = 0; i < x.length; i++) {
if (elmnt != x[i] && elmnt != inp) {
x[i].parentNode.removeChild(x[i]);
}
}
}
/*execute a function when someone clicks in the document:*/
document.addEventListener("click", function (e) {
closeAllLists(e.target);
});
}
/*An array containing all the country names in the world:*/
// var countries = ["Angola", "Anguilla", "Bahamas", "Bahrain", "Bangladesh", "Barbados", "Cambodia", "Cameroon", "Canada", "Dominica", "Dominican Republic", "Ecuador", "Egypt"];
var countries;
$.get("/Home/GetSelectItems", function (response) {
countries = response;
/*initiate the autocomplete function on the "myInput" element, and pass along the countries array as possible autocomplete values:*/
autocomplete(document.getElementById("myInput"), countries.sort());
})
document.getElementById("btnAddNew").addEventListener("click", function (e) {
var newvalue = document.getElementById("inputNewValue").value;
var itemindex = countries.indexOf(newvalue);
if (itemindex == -1) {
countries.push(newvalue);
}
autocomplete(document.getElementById("myInput"), countries.sort());
});
</script>
The result like this (when focus on the input element, it will show the Top 5 items):