Searchble DropDown

Add below references to your form.

full code:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm7.aspx.cs" Inherits="MyWebApp.WebForm7" %>




    
    
    
    
    


    

        

            
                
                
                
                
            
            
            
            
        
    

If you have partial page updates or asynchronous postbacks, you can reinitialize the Select2 plugin after the update. Modify your pageLoad function and the prm.add_endRequest event to ensure the DropDownList is reinitialized after each postback.

function pageLoad(sender, args) {
    $("#<%= ddlBeneficiaryBank.ClientID %>").select2();
}

var prm = Sys.WebForms.PageRequestManager.getInstance();
if (prm != null) {
    prm.add_endRequest(function (sender, e) {
        if (sender._postBackSettings.panelsToUpdate != null) {
            $("#<%= ddlBeneficiaryBank.ClientID %>").select2();
        }
    });
}

Include the above JavaScript code after the Select2 initialization code.

Initialize the Select2 plugin on your DropDownList. You can do this in the

Also, you can refer below link

https://www.aspsnippets.com/Articles/Using-jQuery-Select2-Plugin-with-DropDownList-in-ASPNet.aspx

https://www.w3schools.com/howto/howto_js_filter_dropdown.asp

https://codepen.io/RajRajeshDn/pen/qBBwNbB

https://makitweb.com/make-a-dropdown-with-search-box-using-jquery/

https://stackoverflow.com/questions/36712967/single-dropdown-with-search-box-in-it

https://designmodo.com/create-drop-down-menu-search-box/

https://select2.org/getting-started/basic-usage

pls go through this thank you