DropDownList_SelectedIndexChange Error - Please help! [Answered]RSS

• • Reply
  albasel

  None

  0 Points

  5 Posts

  DropDownList_SelectedIndexChange Error - Please help!

  Apr 19, 2014 07:36 PM|albasel|LINK

  Greeting for all,

  When I run the below code by VB 2013, it returns me back to 

  protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

  I don't know what is going on

  CAN ANY BODY HELP ME TO SOLVE THAT ASAP?

  Thanks in advance.

  My Code is the following:

  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Web;
  using System.Web.UI;
  using System.Web.UI.WebControls;
  using System.Data;
  using System.Data.OleDb;
  using System.Configuration;
  
  public partial class Default2 : System.Web.UI.Page
  {
      protected void Page_Load(object sender, EventArgs e)
      {
          if (!IsPostBack)
          {
              DropDownList1.AppendDataBoundItems = true;
              string CS = "Provider=Microsoft.ACE.OleDb.12.0;Data Source=|DataDirectory|db1.mdb";
              OleDbConnection con = new OleDbConnection(CS);
              OleDbCommand cmd = new OleDbCommand("Select * from [tblCarMaker]", con);
  
              try
              { 
                  con.Open();
                  DropDownList1.DataSource=cmd.ExecuteReader();
                  DropDownList1.DataTextField="Maker_Name";
                  DropDownList1.DataValueField="Maker_ID";
                  DropDownList1.DataBind();
              }
              catch (Exception ex)
              {
                  throw ex;
              }
              finally{
                  con.Close();
                  con.Dispose();
              }
          }
          
      }
      protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
      {
          DropDownList2.Items.Clear();
          DropDownList2.Items.Add(new ListItem("--Select Car Model--", ""));
          DropDownList3.Items.Clear();
          DropDownList3.Items.Add(new ListItem("---Select Car Year--", ""));
  
          DropDownList2.AppendDataBoundItems = true;
  
          string CS = "Provider=Microsoft.ACE.OleDb.12.0;Data Source=|DataDirectory|db1.mdb";
          OleDbConnection con = new OleDbConnection(CS);
          String strQuery = "Select [CarMaker_ID], [Model_Name] , [tblCarMaker].[Maker_ID] from [tblCarModel], [tblCarMaker] where [tblCarMaker].[Maker_ID]=[tblCarModel].[CarMaker_ID];";
          OleDbCommand cmd = new OleDbCommand();
          cmd.Parameters.AddWithValue("CarMaker_ID", DropDownList1.SelectedItem.Value);
          cmd.CommandType= CommandType.Text;
          cmd.CommandText= strQuery;
          cmd.Connection= con;
  
          try
          { 
              con.Open();
              DropDownList2.DataSource=cmd.ExecuteReader();
              DropDownList2.DataTextField="Model_Name";
              DropDownList2.DataValueField="Model_ID";
              DropDownList2.DataBind();
              if (DropDownList2.Items.Count > 1)
              {
                  DropDownList2.Enabled = true;
              }
              else
              {
                  DropDownList2.Enabled = false;
                  DropDownList3.Enabled = false;
              }
          }
          catch (Exception ex)
          {
              throw ex;
          }
          finally{
              con.Close();
              con.Dispose();
          }
  
      }
      protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
      {
          DropDownList3.Items.Clear();
          DropDownList3.Items.Add(new ListItem("--Select Car Year", ""));
          DropDownList3.AppendDataBoundItems = true;
  
          string CS = "Provider=Microsoft.ACE.OleDb.12.0;Data Source=|DataDirectory|db1.mdb";
          OleDbConnection con = new OleDbConnection(CS);
          OleDbCommand cmd = new OleDbCommand("Select [Module_ID], [Car_Year] from [tblCarYear] Where [tblCarModul].[Model_ID]=[tblCarYear].[Modele_ID];", con);
  
          try
          {
              con.Open();
              DropDownList3.DataSource = cmd.ExecuteReader();
              DropDownList3.DataTextField = "Car_Year";
              DropDownList2.DataValueField = "ID";
              DropDownList2.DataBind();
              if (DropDownList3.Items.Count > 1)
              {
                  DropDownList3.Enabled = true;
              }
              else
              {
                  DropDownList2.Enabled = false;
              }
          }
          catch (Exception ex)
          {
              throw ex;
          }
          finally
          {
              con.Close();
              con.Dispose();
          }
  
      }
      protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
      {
          lblResults.Text = "You Selected" +
                          DropDownList1.SelectedItem.Text + "----->" +
                          DropDownList2.SelectedItem.Text + "----->" +
                          DropDownList3.SelectedItem.Text;
      }
  }
      
  

  oledbconnection

• • Reply
  Kevin Shen -...

  All-Star

  16806 Points

  2777 Posts

  Microsoft

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 20, 2014 10:24 PM|Kevin Shen - MSFT|LINK

  Hi albasel,

  About your post ,for you didn’t  post your error message.
  Accodring to your code ,it seems that when you want to change item on DropDownList1 ,then DropDownList2 and DropDownList3   will bind data.

  If  your  problem is that when you click the item in your DropDownList1,But nothing change on your other DropDownLists.

  Please try to set AutoPostBack=”true” ,just like below:

     <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>

  If I misunderstand  your problem,please give me your exact error message ,so that I can recreate in my computer.

   

  Hope it can help you.

  Best Regards,

  Kevin Shen.

  oledbconnection

  Please Mark as Answer If it help you,thanks
• • Reply
  albasel

  None

  0 Points

  5 Posts

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 20, 2014 11:07 PM|albasel|LINK

  I have already set AutoPostBack=”true”

  It doesn' t show me any message only once I choose from dropdownlist1 it return me back to visual studio and highlighting the first bracket of

  protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
  {

  oledbconnection

• • Reply
  Kevin Shen -...

  All-Star

  16806 Points

  2777 Posts

  Microsoft

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 21, 2014 02:28 AM|Kevin Shen - MSFT|LINK

  Hi albasel,

  please set a breakpoint on your method  DropDownList1_SelecteIndexChanged() ,and see the press F11  to debug your application,

  if it has error,please provide your error  message for me, for i write a sample just like you  but it works very well.

  Here is my  page code:

     <div>
          <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>
          <asp:DropDownList ID="DropDownList2" runat="server"></asp:DropDownList>
          <asp:DropDownList ID="DropDownList3" runat="server"></asp:DropDownList>
      </div>

  Here is my server code:

     protected void Page_Load(object sender, EventArgs e)
          {
  
              if (!IsPostBack) {
                  DropDownList1.AppendDataBoundItems = true;
  
                  string sql = "select * from Cus";
                  string connstring = "Data Source=xx;Initial Catalog=xx;User Id=sa;Password=xx;";
                  SqlConnection conn = new SqlConnection(connstring);
                  conn.Open();
                  SqlCommand cmd = new SqlCommand(sql, conn);
                  DropDownList1.DataSource = cmd.ExecuteReader();
                  DropDownList1.DataTextField = "Position_Nm";
                  DropDownList1.DataValueField="PositionId";
                  DropDownList1.DataBind();
              }
          }
  
   protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
          {
              DropDownList2.Items.Clear();
              DropDownList2.Items.Add(new ListItem("--Select Car Model--", ""));
              DropDownList3.Items.Clear();
              DropDownList3.Items.Add(new ListItem("---Select Car Year--", ""));
  
              DropDownList2.AppendDataBoundItems = true;
  
              string sql = "select * from Cus";
              string connstring = "Data Source=xx;Initial Catalog=xx;User Id=sa;Password=xx;";
              SqlConnection conn = new SqlConnection(connstring);
              conn.Open();
              SqlCommand cmd = new SqlCommand(sql, conn);
              DropDownList2.DataSource = cmd.ExecuteReader();
              DropDownList2.DataTextField = "Position_Nm";
              DropDownList2.DataValueField = "PositionId";
              DropDownList2.DataBind();
  
          }

  Hope it can help you.

  Best Regards,

  Kevin Shen.

  oledbconnection

  Please Mark as Answer If it help you,thanks
• • Reply
  albasel

  None

  0 Points

  5 Posts

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 22, 2014 04:43 PM|albasel|LINK

  I have set a breakpoint at my method DropDownList2_SelecteIndexChange() and I have found that the error in

  DropDownList3.DataTextField = "Car_Year"

  I think the error because Car_Year is a number and this parameter should be string

  So, how can I assign a number field to that.

  THANKS

  oledbconnection

• • Reply
  hans_v

  All-Star

  25756 Points

  7014 Posts

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 22, 2014 05:18 PM|hans_v|LINK

  albasel

  DropDownList3.DataSource = cmd.ExecuteReader();
              DropDownList3.DataTextField = "Car_Year";
              DropDownList2.DataValueField = "ID";
              DropDownList2.DataBind();

              DropDownList3.DataSource = cmd.ExecuteReader();
              DropDownList3.DataTextField = "Car_Year";
              DropDownList3.DataValueField = "Module_ID";
              DropDownList3.DataBind();

  oledbconnection

• • Reply
  hans_v

  All-Star

  25756 Points

  7014 Posts

  Re: DropDownList_SelectedIndexChange Error - Please help!

  Apr 22, 2014 05:24 PM|hans_v|LINK

  albasel

  DropDownList2.DataSource=cmd.ExecuteReader();
              DropDownList2.DataTextField="Model_Name";
              DropDownList2.DataValueField="Model_ID";
              DropDownList2.DataBind();

  This is wrong also! Model_ID isn't a fieldname in the command!

  Also, take a look at this:

  http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/CascadingDropDown/CascadingDropDown.aspx

  oledbconnection