How do i retain Dropdown selected after postback too

Question

User2041008840 posted

Hello, 
i am searching list by selecting name from dropdownlist and clicking on search button. 
after postback selected value get reset. How do I retain it after postback too. 
in asp.net core 3.0

Answer 1

User1535942433 posted

Hi Prathamesh,

Accroding to your description, I suggest you could save value in viewdata before return view.Then pass selected dropdown value to controller when click the button.

More details ,you could refer to below codes:

View:

View:
<form>
    <select asp-for="Id" asp-items="@((SelectList)ViewData["vm.Select"])">
        <option>Please select one</option>
    </select>
    <input id="Button1" type="submit" value="button" onclick="Test()"/>

</form>


@section Scripts{
<script>
    function Test() {
         location.href("/home/index");
    }

</script>

Controller:

Model vm = new Model()
        {
            Select = new List<SelectListItem>
            {
                new SelectListItem {Text = "Yellow", Value = "1"},
                new SelectListItem {Text = "Red", Value = "2"},
                new SelectListItem {Text = "Black", Value = "3"},
            }
        };
        public IActionResult Index(string id)
        {
            if(id==null)
            {
                ViewData["vm.Select"] = new SelectList(vm.Select, "Value", "Value");
            }
            else
            {
                ViewData["vm.Select"] = new SelectList(vm.Select, "Value", "Value",id);

            }
            return View(vm);
        }
        [HttpPost]
        public IActionResult Click(string id)
        {
            return RedirectToAction("Index",id);
        }

Model:

public class Model
    {
        public int Id { get; set; }
        public string Color { get; set; }
        public List<SelectListItem> Select { set; get; }
    }

Result:

Best regards,

Yijing Sun

Answer 2

User2041008840 posted

this is helpful sir thank you.