How to change records on viewcomponent via dropdownlist change event?

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ASP.NET-Core

Hi I am new to ASP.NET Core MVC,
I created a ViewComponent that have a dropdownlist and records. I want to when selected index changing of dropdownlist then changing to records. How can i do this? Thanks.

What I have tried:

@model DemirHaberCore.ViewModels.InsaatDemiriViewModel
 
<div class="col-md-2">
    <h4>İnşaat Demiri</h4>
    <div class="form-group">
        @using (Html.BeginForm("InsaatDemiriKaydet", "Yonetim", FormMethod.Post))
        {
            @Html.DropDownListFor(m => m.insaat_Demiri.BolgeId,
           new SelectList(Model.Bolgeler.ToList(), "Id", "Ad"), new
                {
                    @class = "form-control",
            @onchange = "SelectedIndexChanged()" //<----What should i write here and to method?
                }) 
            @Html.LabelFor(m => m.insaat_Demiri.Kalin)
            @Html.TextBoxFor(m => m.insaat_Demiri.Kalin, new { @class = "form-control" })
            @Html.LabelFor(m => m.insaat_Demiri.Ince)
            @Html.TextBoxFor(m => m.insaat_Demiri.Ince, new { @class = "form-control" })
            @Html.HiddenFor(m => m.insaat_Demiri.BolgeId)
            <div><p class="form-control-static"> </p> <button type="submit" class="btn btn-primary ">Kaydet</button></div>
        }
    </div>
</div>