How to refresh table on dropdown selectindexchange in C#

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Actually , i have one dropdown , on selectindexchange of drowndown value of table get change , but next time when i again selectindexchange of dropdown previous value remain in table , i am using autopostback to refresh dropdown

What I have tried:

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
        string query = "select attenday , slot , present from attendance where name = '" + DropDownList1.Text + "'";

        DataTable dtAdmin = new DataTable();
        SqlDataAdapter da;
        da = new SqlDataAdapter(query, con);
        da.Fill(dtAdmin);
        if (dtAdmin.Rows.Count > 0)
           {
                SqlCommand cmd = new SqlCommand(query, con);
                 SqlDataReader dbr;
              
                    con.Open();
                    dbr = cmd.ExecuteReader();
                    while (dbr.Read())
                    {
                        string attenday = (string)dbr["attenday"].ToString();
                        string slot = (string)dbr["slot"].ToString();
                        string presentday = (string)dbr["present"].ToString();

                       
                        if (attenday == "1")
                        {
                            DropDownList2.Text = slot;
                            Label1.Text = presentday;
                        }

                        else if (attenday == "2")
                        {
                            DropDownList3.Text = slot;
                            Label3.Text = presentday;
                        }

                        else if (attenday == "3")
                        {
                            DropDownList4.Text = slot;
                            Label5.Text = presentday;
                        }

                        else if (attenday == "4")
                        {
                            DropDownList5.Text = slot;
                            Label7.Text = presentday;
                        }

                        else if (attenday == "5")
                        {
                            DropDownList6.Text = slot;
                            Label9.Text = presentday;
                        }

                        else if (attenday == "6")
                        {
                            DropDownList7.Text = slot;
                            Label2.Text = presentday;
                        }


                        else if (attenday == "7")
                        {
                            DropDownList8.Text = slot;
                            Label4.Text = presentday;
                        }


                        else if (attenday == "8")
                        {
                            DropDownList9.Text = slot;
                            Label6.Text = presentday;
                        }


                        else if (attenday == "9")
                        {
                            DropDownList10.Text = slot;
                            Label8.Text = presentday;
                        }

                        else if (attenday == "10")
                        {
                            DropDownList11.Text = slot;
                            Label10.Text = presentday;
                        }
                      

                      
                    }

                    dbr.Close();

Posted 9-Jan-18 23:59pm

ADI@345

Updated 10-Jan-18 2:35am

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Comments

Richard Deeming 10-Jan-18 12:34pm

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

Richard Deeming 10-Jan-18 12:36pm

Also, do yourself a favour and give your controls meaningful IDs, rather than just accepting the default ones suggested by Visual Studio.

You might remember which day Label6 refers to now, but when you come back to edit your code in six months, you'll be cursing the person who wrote the code!

Karthik_Mahalingam 10-Jan-18 22:28pm

well said!👍

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Altaf Ansari · Answer 1 · 2018-01-10T02:34:00

Solution 1

if you are calling this Table Bind function on Page Load then Write your function calling inside:

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
       // Call Your Function
    }
}

Posted 10-Jan-18 2:34am

Altaf Ansari

Comments

ADI@345 11-Jan-18 6:37am

I am able to show record in table on dropdown index change but again i select another value in dropdown, previous value remain in table, i need to remove previous value.