所选选项的值不会显示在文本框中

Question

I create a select box with a search box by jquery chosen and I fill it by data from database and I want to show the value of option selected in the text box but when choose an option, nothing show text box so what is the problem and what can I do?

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.5.1/chosen.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.5.1/chosen.jquery.min.js"></script>      

html js code

<div class="span-inside">
    <select runat="server" class="chosen"  
            id="hospSelect"  style="width:350px;">                                 
    </select>
    <input runat="server" type="text" id="hospID" />
    <script type="text/javascript">
        $(".chosen").chosen();
            var txt4 = document.getElementById("hospID");
            var sel4 = document.getElementById("hospSelect");
            sel4.addEventListener("change", function () {
            txt4.value = sel4.value;
        })
    </script>
</div>

c# code

DataBaseConnection db5 = new DataBaseConnection();
db5.disconnect();
string sql5 = "select Hospital_ID , Hospital_Name From TBL_Hospitals";
SqlCommand cmd5 = new SqlCommand(sql5, db5.connect());
hospSelect.DataSource = cmd5.ExecuteReader();

hospSelect.DataTextField = "Hospital_Name";
hospSelect.DataValueField = "Hospital_ID";

hospSelect.DataBind();
hospSelect.Items.Insert(0, "--Choose Hospital--");

Answer 1

txt4.value = sel4.value;

sel4.value; is the value of the whole selection box, which is likely a list or array.

it should be something like sel4.Items.Selected.value; or 'sel4.Selected.value`

Answer 2

Try the below code, to assign the selected drop-down value to the text-box.

$("select.chosen").change(function(){
        var selectedhosp = $(".chosen option:selected").val();
        $('#hospID').val(selectedhosp);
    });