Constant Error 500 Cascading DropDown Lists in AjaxToolkit 4.0 ASP.NET

Im posting the issue down here cause this thing just wrecks my head for the last few weeks actually. I left it for a while but I would really use that tool if I can.

I get the generic Error 500 all the time in the dropdown.

Here's the code for the service:

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


/// <summary>
/// Summary description for inputHoursWS
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, 开发者_高级运维using ASP.NET AJAX, 
//uncomment the following line. 
 [System.Web.Script.Services.ScriptService]
public class inputHoursWS : System.Web.Services.WebService {

    public inputHoursWS () {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public CascadingDropDownNameValue[] getGroupCodes(string knownCategoryValues, 
    string Category)
    {
        InputHoursDSTableAdapters.TMS_ProjectGroupsTableAdapter projectGroupTA = new InputHoursDSTableAdapters.TMS_ProjectGroupsTableAdapter();
        InputHoursDS.TMS_ProjectGroupsDataTable groups = projectGroupTA.GetProjectGroups();

        List<CascadingDropDownNameValue> groupValues = new List<CascadingDropDownNameValue>();

        foreach (DataRow row in groups)
        {

            int groupId = (int)row["ProjectGroupID"];
            string groupCode = (string)row["ProjectGroup"];

            groupValues.Add(new CascadingDropDownNameValue(groupCode, groupId.ToString()));

        }

        return groupValues.ToArray();
    }

 }

Here's the code for the front end web form:

  <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

                    <asp:DropDownList ID="ddlGroups" runat="server" Width="70px" Height="21px">
                     </asp:DropDownList>
                     <asp:CascadingDropDown ID="ddlGroups_CascadingDropDown" 
                      runat="server" 
                      TargetControlID="ddlGroups" 
                      Category="ProjectGroup" 
                      PromptText="Choose a Group" 
                      LoadingText="Please wait ..." 
                      ServicePath="inputHoursWS.asmx" 
                      ServiceMethod="getGroupCodes">
                      </asp:CascadingDropDown>

The methods in the InputHoursDS Dataset are working correctly. I am accessing the developing machine remotely. There's a Visual Web Developer 2010 installed and also the IIS 6 is running .NET 4.0

And a quick question also related - What value do you put in the "Category" attribute on the front end? Is it anything from the database headings or its your own heading?

---

For me adding the below configuration to my web.config file resolved the issue:

<configuration>

  <!-- ... -->

  <system.web.extensions>
    <scripting>
      <webServices>
        <jsonSerialization maxJsonLength="2147483647"/>
      </webServices>
    </scripting>
  </system.web.extensions>

  <!-- ... -->

</configuration>

I'd been seeing the issue in a dropdown which lists the cities available for a given country. Most countries we only had a few cities defined for, but for one there were thousands; it was only that country which errorred; though when debugging the code looked fine (since the called method was running and returning results - the results were just larger than the acceptable size. Amending the max JSON length removed this artificial issue.

---

OK guys, I guess what I didn't realize is that the dataset wasn't set up correctly and actually in another approach I confused the method names.

Use debugging tools such as Fiddler. It really helped me.

To answer my own question. How I understand it is that the category is the primary key column for the next dropdown and the knownCategoryValues are the values of the previous key. Here's a piece of it actually working so that all of you looking for an answer can use it:

[WebMethod]
   public CascadingDropDownNameValue[] getGroups(string knownCategoryValues, string category)
  {
    StringDictionary categoryValues =
 AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(
 knownCategoryValues);

    int countryID = Convert.ToInt32(categoryValues["ProjectGroupID"]);

    List<CascadingDropDownNameValue> cascadingValues =
        new List<CascadingDropDownNameValue>();

    inputHrsDataSetTableAdapters.TMS_ProjectGroupsTableAdapter projectGroupsTA = new inputHrsDataSetTableAdapters.TMS_ProjectGroupsTableAdapter();


    foreach (DataRow _row in projectGroupsTA.GetProjectGroupCodes())
    {
        cascadingValues.Add(new CascadingDropDownNameValue(_row["ProjectGroup"].ToString(),
            _row["ProjectGroupID"].ToString()));

    }

    return cascadingValues.ToArray();
 }

  [WebMethod]
   public CascadingDropDownNameValue[] getProjectNumbers(string knownCategoryValues, string category)
{
    StringDictionary categoryValues =
 AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(
 knownCategoryValues);

    int GroupaID = Convert.ToInt32(categoryValues["ProjectGroupID"]);

    List<CascadingDropDownNameValue> cascadingValues =
        new List<CascadingDropDownNameValue>();

    inputHrsDataSetTableAdapters.TMS_ProjectRegisterTableAdapter projectRegisterTA = new inputHrsDataSetTableAdapters.TMS_ProjectRegisterTableAdapter();


    foreach (DataRow _row in projectRegisterTA.GetProjectNumbersFromGroupID(GroupaID))
    {
        cascadingValues.Add(new CascadingDropDownNameValue(_row["ProjectNumber"].ToString(),
            _row["ProjectNumber"].ToString()));

    }

    return cascadingValues.ToArray();

 }

And Also:

 <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

                                   <asp:DropDownList ID="ddlGroupCodes" runat="server" Height="21px" Width="70px" />

                                   <asp:CascadingDropDown ID="ddlGroupCodes_CascadingDropDown" runat="server" 
                                       TargetControlID="ddlGroupCodes" 
                                       Category="ProjectGroupID"
                                        ServicePath="~/GroupService.asmx"
                                        ServiceMethod="getGroups" 
                                        PromptText="Select Group"
                                         LoadingText="Loading...">
                                   </asp:CascadingDropDown>

                                    <asp:DropDownList ID="ddlProjectNumbers" runat="server" Height="21px" Width="85px" />

                                   <asp:CascadingDropDown ID="ddlProjectNumbers_CascadingDropDown" runat="server" 
                                       TargetControlID="ddlProjectNumbers" 
                                       Category="ProjectNumber"
                                        ServicePath="~/GroupService.asmx"
                                        ServiceMethod="getProjectNumbers" 
                                        PromptText="Select Project No."
                                         LoadingText="Loading..." ParentControlID="ddlGroupCodes">
                                   </asp:CascadingDropDown>

Got all of it nicely thanks to Fiddler! Really, use it for debugging, its awesome.

Again use Debugging tools!!! You don't want to spend a lifetime on a simple misspelling of a method :).