ASP.NET AJAX Cascading Dropdowns – Method error 500
Another one almost driving me crazy. After about 8 hours of digging around I finally found a post that helped:
http://forums.asp.net/thread/1486888.aspx
The problem I was having, like many others, was this: I was trying to implement two cascading dropdown lists using ASP.NET AJAX (following this AJAX video – scroll down to #3 How Do I: Use the ASP.NET AJAX CascadingDropDown Control Extender?) . Everything worked except the second dropdown wouldn’t be filled with values but with error code: Method error 500.
Following the hints in the post help me nail it down. It seems the beta releases of ASP.NET AJAX have been extremely buggy. Many of the posts I found were from this beta period, which creates nightmares when you’re trying to find a solution to your problem. Great feeling when you finally nails it!
Like the video I used an XML file as data store. This is a very simple and fast implementation for small applications. If you want to use a database instead there are some sites that give some guidelines but unfortunely no one gives the whole story. This and this are the best places to start. Also this one contains lots of good info but i was having problems following along in his discussions.
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.NET Ramblings 
dhdfdjc
Hi, I am doing project in ASP.net using C#. I am instructed not to use auto-post back. I need that if anyone select and particular “system” from the dropdown then the “failure” of that system will appear in next dropdown. It should be the noted that both are coming from database with tables ‘system_types’ and ‘failure_types’.
I have tried following AJAX code but it generates error.
I have applied following cascading property.
For DropDownList1
For DropDownList2
After that I have made a class with name “DropDown” and written following code:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using AjaxControlToolkit;
using System.Data.SqlClient;
public class dropdown : System.Web.Services.WebService
{
[WebMethod]
public CascadingDropDownNameValue[] getsystem(String knownCategoryValues, String category)
{
System.Data.SqlClient.SqlConnection sqlCon = new SqlConnection();
sqlCon.ConnectionString = “Data Source=.;Initial Catalog=FTS;Integrated Security=True”;
sqlCon.Open();
System.Data.SqlClient.SqlDataReader sqlReader;
System.Data.SqlClient.SqlCommand sqlCmd = new SqlCommand();
sqlCmd.CommandText = “Select * from system_types”;
sqlCmd.Connection = sqlCon;
sqlReader = sqlCmd.ExecuteReader();
List mysys = new List();
while (sqlReader.Read())
{
String strName = sqlReader[“sys_name”].ToString();
String strId = sqlReader[“sys_id”].ToString();
mysys.Add(new CascadingDropDownNameValue(strName, strId));
}
sqlReader.Close();
sqlReader.Dispose();
sqlCon.Close();
sqlCon.Dispose();
return mysys.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] getfailure(String knownCategoryValues, String category)
{
System.Data.SqlClient.SqlConnection sqlCon = new SqlConnection();
sqlCon.ConnectionString = “Data Source=.;Initial Catalog=FTS;Integrated Security=True”;
sqlCon.Open();
System.Data.SqlClient.SqlDataReader sqlReader;
System.Data.SqlClient.SqlCommand sqlCmd = new SqlCommand();
sqlCmd.CommandText = “Select * from failure_types”;
sqlCmd.Connection = sqlCon;
sqlReader = sqlCmd.ExecuteReader();
StringDictionary kvTeam = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
Int32 intConfId;
if (!kvTeam.ContainsKey(“system_types”) || !Int32.TryParse(kvTeam[“system_types”], out intConfId))
{
return null;
}
sqlCmd.Parameters.AddWithValue(“@confid”, intConfId);
List myfail = new List();
while (sqlReader.Read())
{
String strTeamName = sqlReader[“failure_name”].ToString();
String strTeamId = sqlReader[“team_id”].ToString();
myfail.Add(new CascadingDropDownNameValue(strTeamName, strTeamId));
}
sqlReader.Close();
sqlReader.Dispose();
sqlCon.Close();
sqlCon.Dispose();
return fail.ToArray();
}
Next, I have called these two method DropDownList1_SelectedIndexChanged event with following code.
dropdown dr = new dropdown();
dr.getfailure(DropDownList1.SelectedValue, DropDownList1.Text);
When I run it, It give [Method error 500] in both dropdown.
Please correct me, I have very short time.
I want that first downdownlist1 should be filled with value from table name “system_types” and dropdownlist2 should filled with value from table with “failure types”.
hi
i have the same issue
just add
sing AjaxControlToolkit;
using System.Collections.Specialized;
[WebService(Namespace = “http://tempuri.org/”)]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
before the public class dropdown : System.Web.Services.WebService
Next, I have called these two method DropDownList1_SelectedIndexChanged event with following code.
dropdown dr = new dropdown();
dr.getfailure(DropDownList1.SelectedValue, DropDownList1.Text);
When I run it, It give [Method error 500] in both dropdown.
Please correct me, I have very short time.
I want that first downdownlist1 should be filled with value from table name “system_types” and dropdownlist2 should filled with value from table with “failure types”.
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