why selected.value does not work

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Hi I have 4 DropDownList in asp.net vs c# and in app_code I have this code to fill ddl from database:

public void fillddl(DropDownList ddl, string tablename, string textfieldname, string valuefieldname)
   {
       SqlConnection scon = new SqlConnection(cstr);
       scon.Open();
       string selectstr = string.Format("SELECT {0},{1} FROM {2}",

                                        textfieldname,
                                        valuefieldname,
                                        tablename);
       SqlDataAdapter sda = new SqlDataAdapter(selectstr,scon );
       DataSet ds = new DataSet();
       sda.Fill(ds);
       ddl.DataSource = ds;
       ddl.DataTextField = textfieldname;
       ddl.DataValueField = valuefieldname;
       ddl.DataBind();
       scon.Close();

   }

and in page_load I have this code :

if (!Page.IsPostBack)
        {
            dbmanager dbm = new dbmanager();
            dbm.fillddl(DropDownList1, "my_tbl", "year", "price");
            dbm.fillddl(DropDownList2, "my_tbl", "year", "price");
            dbm.fillddl(DropDownList3, "my_tbl", "year", "price");
            dbm.fillddl(DropDownList4, "my_tbl", "year", "price");
        }

and this code:

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
   {
       Label1.Text = DropDownList1.SelectedValue.ToString();
   }
   protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
   {
       Label2.Text = DropDownList2.SelectedValue.ToString();
   }
   protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
   {
       Label3.Text = DropDownList3.SelectedValue.ToString();
   }
    protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e)
   {
       Label4.Text = DropDownList4.SelectedValue.ToString();
   }

suppose that year_field in my ddl values are:
2012
2013
2014
2015
and price_value:
100
200
100
400
the problem is that when I select 2012 or 2014 ( the price of them are same and equal) the ddl selected does not changed. but for other year (which theire price are different)ddlselected value changed and work good.
please help me!

Posted 16-Nov-15 3:50am

rezaeti

Updated 21-Nov-15 1:22am

v5

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Comments

John C Rayan 16-Nov-15 10:10am

Your question is not very clear. You are missing one selectedindexchanged() code for fourth dropdown. Are you sure that the viewstate enabled for all the ddls

rezaeti 16-Nov-15 10:31am

hi thanks for reply
viewstate enabled for all the ddls is true.
my question is:
suppose that my ddl items are:
2012
2013
2014
2015
when I select 2013 the ddl item does not select and item 2012 be selected. but for other items work correctly

rezaeti 16-Nov-15 10:42am

all of ddl work correctly but one of item for all ddl does not selected

John C Rayan 16-Nov-15 11:14am

Can you check the value for the item 2013 in select from HTML. Are you getting a value ? I assume that you are talking about code behind not the state in the ddl.

rezaeti 16-Nov-15 13:26pm

yes my above code is code behind.how to solve my problem?

John C Rayan 17-Nov-15 6:44am

check your data binding for your ddl. Debug and see all the key and value for dll, it looks like the item you mentioned has got null key.

Anil Sharma1983 23-Nov-15 4:10am

please check selected index event all dropdown aspx page

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rezaeti · Accepted Answer · 2015-11-27T02:03:00

Hi. I Self Solved The Problem :
First I Add a GridView in My Form
Then I Changed Codes As Follow:

C#

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            dbmanager dbm = new dbmanager();
            dbm.loaddataingrid("select * from dieh", GridView1);
            dbm.fillddl(DropDownList1, "my_tbl", "year", "id");
            dbm.fillddl(DropDownList2, "my_tbl", "year", "id");
            dbm.fillddl(DropDownList3, "my_tbl", "year", "id");
            dbm.fillddl(DropDownList4, "my_tbl", "year", "id");

        }
    }

and :

C#

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string i = DropDownList1.SelectedIndex.ToString();
        Label1.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text; 
    }
    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        string i = DropDownList2.SelectedIndex.ToString();
        Label2.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text; 
    }
    protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
    {
        string i = DropDownList3.SelectedIndex.ToString();
        Label3.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text; 
    }
    protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e)
    {
        string i = DropDownList4.SelectedIndex.ToString();
        Label4.Text = GridView1.Rows[int.Parse(i)].Cells[1].Text; 
    }