My dropdownlist just allow selecting one item once I select item2 it retrieve and select item1

Question

1.00/5 (1 vote)

See more:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Text;
using System.Messaging;
using System.Net;
using System.Net.Mail;


namespace exam
{
    public partial class CreatAgroup : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["seniorConnectionString"].ConnectionString);
            con.Open();
            using (SqlCommand cmd = new SqlCommand("select st_name,STID from dbo.[Student] ", con))
            {

                using (SqlDataReader read = cmd.ExecuteReader())
                {




                    DropDownList3.DataSource =  read ;


                    DropDownList3.DataTextField = "st_name";
                    DropDownList3.DataValueField = "STID";

                    DropDownList3.DataBind();
                }
            }
            using (SqlCommand cmd = new SqlCommand("select S_name,SID from dbo.[Suporvisor(commtiee)] ", con))
            {

                using (SqlDataReader read = cmd.ExecuteReader())
                {




                    DropDownList2.DataSource = read;


                    DropDownList2.DataTextField = "S_name";
                    DropDownList2.DataValueField = "SID";

                    DropDownList2.DataBind();
                }
            }
           
            

        }
        protected void DropDownList2_SelectedIndexChanged(Object Sender, EventArgs e)
        {
            Label1.Text = DropDownList2.SelectedValue.ToString();
            
        }
        protected void DropDownList3_SelectedIndexChanged(Object Sender, EventArgs e)
        {
            Label2.Text = DropDownList3.SelectedValue.ToString();

             
        }
          
    }
} if i want for example select second name in drowpdown list it is just allow select the first one

And this source code
<pre><%@ Page Language="C#" AutoEventWireup="true" CodeBehind="CreatAgroup.aspx.cs" Inherits="exam.CreatAgroup" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
        .auto-style1 {
            text-align: center;
            font-size: xx-large;
        }
        .auto-style2 {
            width: 100%;
        }
        .auto-style3 {
            width: 486px;
        }
        .auto-style4 {
            margin-left: 932px;
            margin-top: 69px;
        }
        .auto-style5 {
            width: 278px;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <p class="auto-style1">
            Add Group for Sineor Project</p>
        <p class="auto-style1">
             </p>
        <table class="auto-style2">
            <tr>
                <td class="auto-style3">Student</td>
                <td>Suporvisor</td>
            </tr>
            <tr>
                <td class="auto-style3">
                    <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DropDownList3_SelectedIndexChanged">
                    </asp:DropDownList>
                </td>
                <td>
                    <asp:DropDownList ID="DropDownList2" runat="server"  AutoPostBack="true" Height="42px" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged" Width="255px">
                    </asp:DropDownList>
                </td>
            </tr>
        </table>
        <p>
             </p>
        <table class="auto-style2">
            <tr>
                <td class="auto-style5">Selected Student name</td>
                <td>
                    <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
                </td>
            </tr>
            <tr>
                <td class="auto-style5">Selected Suporvisor name</td>
                <td>
                    <asp:Label ID="Label2" runat="server" Text="Label"></asp:Label>
                </td>
            </tr>
        </table>
        <p>
             </p>
        <p>
             </p>
        <p>
             </p>
        <p>
             </p>
        <p>
             </p>
        <p>
             Create a Groub   <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
        </p>
        <asp:Button ID="Button1" runat="server" CssClass="auto-style4" Height="52px" Text="Add Groub" Width="347px" />
    </form>
</body>
</html>

What I have tried:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Text;
using System.Messaging;
using System.Net;
using System.Net.Mail;


namespace exam
{
    public partial class CreatAgroup : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["seniorConnectionString"].ConnectionString);
            con.Open();
            using (SqlCommand cmd = new SqlCommand("select st_name,STID from dbo.[Student] ", con))
            {

                using (SqlDataReader read = cmd.ExecuteReader())
                {




                    DropDownList3.DataSource =  read ;


                    DropDownList3.DataTextField = "st_name";
                    DropDownList3.DataValueField = "STID";

                    DropDownList3.DataBind();
                }
            }
            using (SqlCommand cmd = new SqlCommand("select S_name,SID from dbo.[Suporvisor(commtiee)] ", con))
            {

                using (SqlDataReader read = cmd.ExecuteReader())
                {




                    DropDownList2.DataSource = read;


                    DropDownList2.DataTextField = "S_name";
                    DropDownList2.DataValueField = "SID";

                    DropDownList2.DataBind();
                }
            }
           
            

        }
        protected void DropDownList2_SelectedIndexChanged(Object Sender, EventArgs e)
        {
            Label1.Text = DropDownList2.SelectedValue.ToString();
            
        }
        protected void DropDownList3_SelectedIndexChanged(Object Sender, EventArgs e)
        {
            Label2.Text = DropDownList3.SelectedValue.ToString();

             
        }
          
    }
}

Posted 29-Feb-20 10:01am

Member 14757261

Updated 3-Mar-20 1:47am

Rick York

v4

Add a Solution

Comments

phil.o 2-Mar-20 3:36am

Unclear. What behaviour are you expecting? Which one do you experience instead?
Please improve your question.

Stefan_Lang 2-Mar-20 7:59am

This looks like C#, not C++. Please set the correct tags on your question.

Also you mixed code, Your explanatory text, and some HTML source into the code formatting. Please separate these and use the appropriate formatting for each.

Finally, when you post so much code, you should put in some effort to point out where in the code it is not working as expected. That is very little work for you, but takes a lot of effort for anyone trying to help.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

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

Richard Deeming · Answer 1 · 2020-03-03T01:47:00

You are re-binding both lists on every page load. You need to wrap that code in an if (!IsPostBack) test.

Also, wrap your SqlConnection in a using block.

And the SelectedValue already returns a string; there's no need to call .ToString() on it.

C#

public partial class CreatAgroup : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["seniorConnectionString"].ConnectionString))
            {
                con.Open();
                using (SqlCommand cmd = new SqlCommand("select st_name, STID from dbo.[Student]", con))
                using (SqlDataReader read = cmd.ExecuteReader())
                {
                    DropDownList3.DataSource =  read;
                    DropDownList3.DataTextField = "st_name";
                    DropDownList3.DataValueField = "STID";
                    DropDownList3.DataBind();
                }
                
                using (SqlCommand cmd = new SqlCommand("select S_name, SID from dbo.[Suporvisor(commtiee)]", con))
                using (SqlDataReader read = cmd.ExecuteReader())
                {
                    DropDownList2.DataSource = read;
                    DropDownList2.DataTextField = "S_name";
                    DropDownList2.DataValueField = "SID";
                    DropDownList2.DataBind();
                }
            }
        }
    }
    
    protected void DropDownList2_SelectedIndexChanged(Object Sender, EventArgs e)
    {
        Label1.Text = DropDownList2.SelectedValue;
    }
    
    protected void DropDownList3_SelectedIndexChanged(Object Sender, EventArgs e)
    {
        Label2.Text = DropDownList3.SelectedValue;
    }
}

NB: You should avoid using "special" characters in your SQL table and column names. Stick to using A-Z, 0-9, and the underscore character _. As you've discovered, using "special" characters makes your queries harder to write, because you have to enclose the name in square brackets.