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CascadingDropDown in Ajax With ASP.net

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11 Oct 2013CPOL3 min read 7.7K   1  
Step1: Create a table in database:- create table test( state1 varchar(50),city varchar(50)  )  Step2:- In the .aspx Page:-   <select id="statelist"

This articles was originally at wiki.asp.net but has now been given a new home on CodeProject. Editing rights for this article has been set at Bronze or above, so please go in and edit and update this article to keep it fresh and relevant.

Step1: Create a table in database:-

 

create table test

(

 state1 varchar(50),

city varchar(50)  

 

Step2:- In the .aspx Page:-

 

  <select id="statelist" runat="server" onchange="showCity()" style="width: 160px">

                            <option></option>

                        </select>

                        <asp:DropDownList ID="citylist" runat="server" Width="184px">

                        </asp:DropDownList>

 

 

Take statelist for State and citylist for City 

When you select any item from statelist the citylist will automatically fill because of ajax 

 

Step3:-  Write this in the <head> Part:-

  <script language="JavaScript" type="text/javascript" >


var xmlHttp

var arr;

function showCity()

{


xmlHttp=GetXmlHttpObject()

var url="Default.aspx"

url=url+"?name="+document.getElementById('statelist').value

xmlHttp.onreadystatechange=stateChanged 

xmlHttp.open("GET",url,true)

xmlHttp.send(null)

return false;

}


function stateChanged() 

if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")

            var str;

            str = xmlHttp.responseText;

            

           arr=str.split(",");

           var i;

           for(i=0;i<arr.length;i++)

           {

               dd2= document.getElementById("citylist")

                

                var theOption = new Option;

                theOption.text = arr[i];

                theOption.value = arr[i];

                dd2.options[i] = theOption;

           }


function GetXmlHttpObject()

var objXMLHttp=null

if (window.XMLHttpRequest)

{

objXMLHttp=new XMLHttpRequest()

}

else if (window.ActiveXObject)

{

objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")

}

return objXMLHttp

   

</script>

 

Step 4:-  in the .cs page:-

 

SqlConnection con = new SqlConnection("data source = MY\\SQLEXPRESS; initial catalog = try; integrated security=true");

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!Page.IsPostBack)

        {

            con.Open();

            SqlCommand cmd = new SqlCommand("select * from test", con);

            SqlDataReader dr;

            dr = cmd.ExecuteReader();


            statelist.DataSource = dr;

            statelist.DataTextField = "state";

            statelist.DataBind();

            dr.Close();

            con.Close();

        }


        if (Request.QueryString["name"] != null)

        {

            string name = Request.QueryString["name"];

            Response.Clear();

            con.Open();

            SqlCommand cmd = new SqlCommand("select * from test where state=@state", con);

            cmd.Parameters.AddWithValue("@state", name);

            SqlDataReader dr;

            dr = cmd.ExecuteReader();

            string str = "";

            int a = 0;

            while (dr.Read())

            {

                if (a == 0)

                    str += dr["city"].ToString();

                else

                    str += "," + dr["city"].ToString();


                a++;

            }

            Response.Write(str);


            Response.End();

            con.Close();


        }

    } 


License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
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