Cascading Dropdown Using Ajax and webservices

Question

User1173249824 posted

Hi Pls I av been working on cascading a dropdownlist with ajax but the issue is I have completely finished with my coding, passing parameters, but the isue is that when ever I run my Webservices, and I invoked my BindFolder and BindSubfolder, it tells me that value cannot be null. but the BindArchive is working properly

here is my code:

public class WebService : System.Web.Services.WebService {
     SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["dbConnectStrings"].ConnectionString);
   // Bind Archive
    
    [WebMethod]
    public CascadingDropDownNameValue[] BindArchive(string knownCategoryValues, string category) 
    {
       DataSet ds = new DataSet();
        conn.Open();//select * from [ST-Dep]
        SqlCommand cmd = new SqlCommand("select distinct empd.arc, empc.EmpCategoryId,empc.EmpCategoryName from Doc empd INNER JOIN EmpCategory empc On empd.arc = empc.EmpCategoryId", conn);
        SqlDataAdapter adp = new SqlDataAdapter(cmd);
        cmd.ExecuteNonQuery();
        adp.Fill(ds);
        conn.Close();

        List<CascadingDropDownNameValue> ArchiveDetails = new List<CascadingDropDownNameValue> ();
        foreach (DataRow Dr in ds.Tables[0].Rows)
        {
            string ArcID = Dr["arc"].ToString();
            string ArcName = Dr["EmpCategoryName"].ToString();

            ArchiveDetails.Add(new CascadingDropDownNameValue(ArcName, ArcID));

    }
    return ArchiveDetails.ToArray();
}
    //Folder
    [WebMethod]
    public CascadingDropDownNameValue[] BindFolder(string knownCategoryValues, string category)
    {
    DataSet ds = new DataSet();
    char ArcID;
    StringDictionary ArchiveDetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
    ArcID = Convert.ToChar(ArchiveDetails["arc"]);
    conn.Open();//SELECT  * From [ST-Dep] where DepId=@DepId
    SqlCommand cmd = new SqlCommand("select distinct empd.folder,dep.DepId,dep.DepName From Doc empd INNER JOIN [ST-Dep] dep ON empd.folder = dep.DepId where empd.archive= @DepId ", conn);
    cmd.Parameters.AddWithValue("@DepId", ArcID);
    cmd.ExecuteNonQuery();
        SqlDataAdapter adp = new SqlDataAdapter(cmd);
        adp.Fill(ds);
        conn.Close();
         List<CascadingDropDownNameValue> FolderDetails = new List<CascadingDropDownNameValue> ();
        foreach (DataRow Dr in ds.Tables[0].Rows)
        {
            string FolderID = Dr["folder"].ToString();
            string FolderName = Dr["DepName"].ToString();
            FolderDetails.Add(new CascadingDropDownNameValue(FolderName, FolderID));
        }
        return FolderDetails.ToArray();
        }
    //SubFolder bind
    [WebMethod]
    public CascadingDropDownNameValue[] BinSubfolder(string knownCategoryValues, string category)
    {
        DataSet ds = new DataSet();
        char FolderID;
        StringDictionary folderdetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
        FolderID = Convert.ToChar(folderdetails["DepName"]);
        conn.Open();//Select * From Doc where folder = @Folder
        SqlCommand cmd = new SqlCommand("select distinct empd.subfolder, trad.TradeId, trad.TradeName From Doc empd INNER JOIN [Trade] trad ON empd.subfolder = trad.TradeId where (empd.folder = @Folder)", conn);
        cmd.Parameters.AddWithValue("@Folder", FolderID);
        cmd.ExecuteNonQuery();
        SqlDataAdapter adp = new SqlDataAdapter(cmd);
        adp.Fill(ds);
        conn.Close();
        List<CascadingDropDownNameValue> SubFoldetails = new List<CascadingDropDownNameValue>();
        foreach (DataRow dr in ds.Tables[0].Rows)
        {
            string SubFolID = dr["subfolder"].ToString();
            string subFolName = dr["TradeName"].ToString(); 
 SubFoldetails.Add(new CascadingDropDownNameValue(subFolName, SubFolID)); } return SubFoldetails.ToArray(); } }

and Here is my Category in my CASCADINGDROPDOWN

<asp:CascadingDropDown ID="ccarchive" runat="server" Category="arc" TargetControlID="ddarchive" LoadingText="Loading Archives.." PromptText="Select Archive" ServiceMethod="BindArchive" ServicePath="~/WebService.asmx"   />

  <asp:CascadingDropDown ID="ccFolder" runat="server" Category="DepId" TargetControlID="ddFolder" ParentControlID="ddarchive" LoadingText="Loading Folders.." PromptText="Select Folder" ServiceMethod="BindFolder" ServicePath="~/WebService.asmx" />

 <asp:CascadingDropDown ID="ccSubfolder" runat="server" Category ="TradeId"  TargetControlID ="ddSubfolder" ParentControlID ="ddFolder" LoadingText="Loading SubFolders" PromptText ="Select SubFolder" ServiceMethod="BindSubfolder" ServicePath="~/WebService.asmx"/>  
       

Ps can som1 elp me out with what might av been causing it to retun a null value

Thanks

Answer 1

User1970566204 posted

alamdreal1

//SubFolder bind
    [WebMethod]
    public CascadingDropDownNameValue[] BinSubfolder(string knownCategoryValues, string category)
    {
        DataSet ds = new DataSet();
        char FolderID;
        StringDictionary folderdetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
        /*****  FolderID = Convert.ToChar(folderdetails["DepName"]); *******/

FolderID = Convert.ToChar(folderdetails["DepId"]);

Answer 2

User1173249824 posted

asyed4u

FolderID = Convert.ToChar(folderdetails["DepId"]);

Its Still give thesame error  value cannot be null @ FolderID = Convert.ToChar(folderdetails["DepId"]);

what might be the cause pls

Thanks

Answer 3

User1970566204 posted

Hi,

 when i worked your code , [ i connect with northwind]

its produce two error,

1)  closing class blcok

2) method name mismatch 

ServiceMethod="BindSubfolder"

     but in Servicee ........ BinSubFolder()

After these two fix, you code works fine,

Try like above , otherwise i will post entire my working sample 

Answer 4

User1970566204 posted

1 .WebService1.asmx

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Web.Services;
using AjaxControlToolkit;

namespace WebApplication8
{
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    [System.Web.Script.Services.ScriptService]
    public class WebService1 : WebService
    {
        private SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString);
        [WebMethod]
        public CascadingDropDownNameValue[] BindArchive(string knownCategoryValues, string category)
        {
            DataSet ds = new DataSet();
            conn.Open(); //select * from [ST-Dep]
            SqlCommand cmd = new SqlCommand("SELECT CategoryID as arc ,CategoryName as EmpCategoryName FROM Categories", conn);
            SqlDataAdapter adp = new SqlDataAdapter(cmd);
            cmd.ExecuteNonQuery();
            adp.Fill(ds);
            conn.Close();
            List<CascadingDropDownNameValue> ArchiveDetails = new List<CascadingDropDownNameValue>();
            foreach (DataRow Dr in ds.Tables[0].Rows)
            {
                string ArcID = Dr["arc"].ToString();
                string ArcName = Dr["EmpCategoryName"].ToString();
                ArchiveDetails.Add(new CascadingDropDownNameValue(ArcName, ArcID));
            }
            return ArchiveDetails.ToArray();
        }
        [WebMethod]
        public CascadingDropDownNameValue[] BindFolder(string knownCategoryValues, string category)
        {
            DataSet ds = new DataSet();
            string ArcID; //char ArcID;  //only for my purpose
            StringDictionary ArchiveDetails = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
            // ArcID = Convert.ToChar(ArchiveDetails["arc"]); //only for my purpose
            ArcID = Convert.ToString(ArchiveDetails["arc"]);
            conn.Open(); //SELECT  * From [ST-Dep] where DepId=@DepId
            SqlCommand cmd = new SqlCommand("SELECT SupplierID as folder ,ProductName as DepName FROM Products where CategoryID=@DepId", conn);
            cmd.Parameters.AddWithValue("@DepId", ArcID);
            cmd.ExecuteNonQuery();
            SqlDataAdapter adp = new SqlDataAdapter(cmd);
            adp.Fill(ds);
            conn.Close();
            List<CascadingDropDownNameValue> FolderDetails = new List<CascadingDropDownNameValue>();
            foreach (DataRow Dr in ds.Tables[0].Rows)
            {
                string FolderID = Dr["folder"].ToString();
                string FolderName = Dr["DepName"].ToString();
                FolderDetails.Add(new CascadingDropDownNameValue(FolderName, FolderID));
            }
            return FolderDetails.ToArray();
        }
        //SubFolder bind
        [WebMethod]                  /*BinSubfolder*/
        public CascadingDropDownNameValue[] BindSubfolder(string knownCategoryValues, string category)                                        
        {
            DataSet ds = new DataSet();
            string FolderID;   //char FolderID; //only for my purpose
            StringDictionary folderdetails = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
            //FolderID = Convert.ToChar(folderdetails["DepId"]); //only for my purpose
            FolderID = Convert.ToString(folderdetails["DepId"]);
            conn.Open(); //Select * From Doc where folder = @Folder
            SqlCommand cmd = new SqlCommand("SELECT SupplierID as subfolder,CompanyName as TradeName FROM Suppliers where SupplierID=@Folder ", conn);
            cmd.Parameters.AddWithValue("@Folder", FolderID);
            cmd.ExecuteNonQuery();
            SqlDataAdapter adp = new SqlDataAdapter(cmd);
            adp.Fill(ds);
            conn.Close();
            List<CascadingDropDownNameValue> SubFoldetails = new List<CascadingDropDownNameValue>();
            foreach (DataRow dr in ds.Tables[0].Rows)
            {
                string SubFolID = dr["subfolder"].ToString();
                string subFolName = dr["TradeName"].ToString();
                SubFoldetails.Add(new CascadingDropDownNameValue(subFolName, SubFolID));
            }
            return SubFoldetails.ToArray();
        }
    }
}

2.webform1.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication8.WebForm1" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>MyDemo-CascadingDropDown for asp.net</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
        <div>
            Category :
            <asp:DropDownList ID="ddarchive" runat="server"></asp:DropDownList>
            <asp:CascadingDropDown ID="ccarchive" runat="server" Category="arc" TargetControlID="ddarchive" LoadingText="Loading Archives.." PromptText="Select Archive" ServiceMethod="BindArchive" ServicePath="WebService1.asmx" />
            <br />
            Products :
            <asp:DropDownList ID="ddFolder" runat="server"></asp:DropDownList>
            <asp:CascadingDropDown ID="ccFolder" runat="server" Category="DepId" TargetControlID="ddFolder" ParentControlID="ddarchive" LoadingText="Loading Folders.." PromptText="Select Folder" ServiceMethod="BindFolder" ServicePath="WebService1.asmx" />
            <br />
            Supplier :
            <asp:DropDownList ID="ddSubfolder" runat="server"></asp:DropDownList>
            <asp:CascadingDropDown ID="ccSubfolder" runat="server" Category="TradeId" TargetControlID="ddSubfolder" ParentControlID="ddFolder" LoadingText="Loading SubFolders" PromptText="Select SubFolder" ServiceMethod="BindSubfolder" ServicePath="WebService1.asmx" />
        </div>
    </form>
</body>
</html>