ASP.NET

Dropdown list value is not retaining on page post back [modified]

31-Aug-09 14:00

monu_khan wrote:
TextBox1.Text.Length

This is more than a little insane. You need to use MeasureString to get a width and height.

monu_khan wrote:
Graphics g = Graphics.FromImage(b);

Why not use a using statement, instead of leaking resources ?

monu_khan wrote:
new Font("Kruti Dev 010", 12, FontStyle.Regular)

Another leak, plus if you change the font, it means you need to measure the string for that font.

Although you're using ASP.NET, this question has nothing to do with ASP.NET, it's about some basic graphics work. Why do you waste server space by saving a string a a bitmap instead of as text ?

monu_khan wrote:
int alignment = 1;
if (alignment == 1)

Bizarre.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

skhan1731-Aug-09 7:10

skhan17

31-Aug-09 7:10

Dear all,
I am having problem with placing the proper condition inside the postback method. I am trying to do the following:
1. There are 2 dropdown lists in my program.
2. I have two DropDownLists databound on the webform. The autopostback of the first dropdown list control is set to true. The contents of the first dropdown list is hardcoded. The contents of the second depend on the selected item in the first. In other words: The selectedvalue of the first DropDownList is passed as a parameter for the query at the basis of the second DropDownList's datasource. And this works: Whenever I click on an item in the first DropDownList, the dependant items are shown in the second DropDownList.

3. If I click submit then the specific rows from the DB will be pulled based on the values selected from dropdown list 1 and dropdown list 2.

Problem: In the postback method I think all the times the "ANY" MLNO is selected instead of selecting a specific value from the dropdown list 2. And that's why always all the values are pulled from the DB.

The code is as follows:
Code:

using System.Data;
using System.Data.OleDb;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.IO;
using System.Xml;
using System.Globalization;


namespace HIV
{
    /// &lt;summary&gt;
    /// Summary description for run_specific_query.
    /// &lt;/summary&gt;
    public class run_specific_query : System.Web.UI.Page
    {
        protected HIV.Controls.NavMenu navMenu;
        protected HIV.Controls.NavSubMenu navSubMenu;
        protected System.Web.UI.HtmlControls.HtmlGenericControl message;
        protected System.Web.UI.WebControls.Label resultsLabel;
        protected System.Web.UI.WebControls.DropDownList Specific_Query_DDL;
        protected System.Web.UI.WebControls.DropDownList mlno_DDL;
        //protected System.Web.UI.WebControls.TextBox date_TB;
        protected System.Web.UI.WebControls.CompareValidator dateValidator;
        protected System.Web.UI.WebControls.DataGrid resultsDatagrid;
        protected System.Web.UI.WebControls.Button submitButton;
        protected System.Web.UI.WebControls.Label data_src;
        protected System.Web.UI.WebControls.LinkButton exportLinkbutton;

        private void Page_Load(object sender, System.EventArgs e)
        {
            navMenu.SelectedMainItem = HIV.Controls.NavMenu.MainItems.QUERY;
            navSubMenu.SelectedMainItem = HIV.Controls.NavMenu.MainItems.QUERY;
            navSubMenu.SelectedSubItem = HIV.Controls.NavSubMenu.SubItems.RUN_SPECIFIC_QUERY;
            
            if (this.IsPostBack)
            {
                if(Specific_Query_DDL.SelectedItem.Value=="ResistantL")
                {
                    getMLNO(Specific_Query_DDL.SelectedItem.Value);
                }
                if(Specific_Query_DDL.SelectedItem.Value=="NegativeL")
                {
                    getMLNO(Specific_Query_DDL.SelectedItem.Value);
                }
           }
           
        }

        #region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            BuildQueryForm();
            InitializeComponent();
            base.OnInit(e);
        }
        
        /// &lt;summary&gt;
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// &lt;/summary&gt;
        private void InitializeComponent()
        {    
            this.exportLinkbutton.Click += new System.EventHandler(this.exportLinkbutton_Click);
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

        protected void BuildQueryForm()
        {
            try
            {
                this.submitButton.Click += new System.EventHandler(this.submitButton_Click);
                this.Load += new System.EventHandler(this.Page_Load);
            }
            catch(Exception e)
            {
                message.InnerHtml = "Exception: " + e.ToString();
            }
        }

        private void getMLNO(string selectedvalue)
        {
            if(selectedvalue=="ResistantL")
            {
                string sql= "SELECT re_MLNO, MAX(re_SpecimenDate)-MIN(re_SpecimenDate) AS DaysSeronegative FROM ml_hiv_status WHERE (re_HIV1_Status=0) GROUP BY re_MLNO";
            
                OleDbConnection connection = new OleDbConnection(HIV.Database.DataConstants.CONNECTION_STRING);
                OleDbDataAdapter adapter = new OleDbDataAdapter();
                OleDbCommand command = new OleDbCommand(sql, connection);
            
                DataSet ds = new DataSet();
                adapter.SelectCommand = command;

                if (adapter.Fill(ds) &gt; 0)
                {
                    foreach (DataRow r in ds.Tables[0].Rows)
                    {
                        if(Convert.ToInt32(r["DaysSeronegative"]) &lt; 2555)  
                        {
                            r.Delete();
                        }
                    }
                    DataView view = ds.Tables[0].DefaultView;
                    mlno_DDL.DataSource = view;
                    mlno_DDL.DataValueField="re_MLNO";
                    mlno_DDL.DataTextField = "re_MLNO";
                    mlno_DDL.DataBind();
                    resultsLabel.Visible= true;
                    mlno_DDL.Items.Insert(0, "ANY");
                }
                connection.Close();
            }
            if(selectedvalue=="NegativeL")
            {
                string sql= "SELECT re_MLNO,sum(re_HIV1_Status) AS hivNeg, MAX(re_SpecimenDate)- MIN(re_SpecimenDate) AS DaysSeronegative  FROM ml_hiv_status  GROUP BY re_MLNO";

                OleDbConnection connection = new OleDbConnection(HIV.Database.DataConstants.CONNECTION_STRING);
                OleDbDataAdapter adapter = new OleDbDataAdapter();
                OleDbCommand command = new OleDbCommand(sql, connection);
            
                DataSet ds = new DataSet();
                adapter.SelectCommand = command;

                if (adapter.Fill(ds) &gt; 0)
                {
                    foreach (DataRow r in ds.Tables[0].Rows)
                    {
                        if(Convert.ToInt32(r["hivNeg"]) != 0)
                        {
                            r.Delete();
                        }
                    }
                    DataView view = ds.Tables[0].DefaultView;
                    mlno_DDL.DataSource = view;
                    mlno_DDL.DataValueField="re_MLNO";
                    mlno_DDL.DataTextField = "re_MLNO";
                    mlno_DDL.DataBind();
                    resultsLabel.Visible= true;
                    mlno_DDL.Items.Insert(0, "ANY");
                }
                connection.Close();
            }
            
        }
        private void listBox1_SelectedIndexChanged(object sender, System.EventArgs e)
        {
        }
        private void submitButton_Click(object sender, System.EventArgs e)
        {
            if(Specific_Query_DDL.SelectedItem.Value=="default")
            {
                resultsLabel.Visible= true;
                resultsLabel.Text ="Please select a specific query from the dropdown list";
                exportLinkbutton.Visible = false;
            }
            if(Specific_Query_DDL.SelectedItem.Value=="ResistantL")
            {
                if(mlno_DDL.SelectedItem.Value=="ANY")
                {
                    executeResistantListQuery_ANY();
                }    
                else if(mlno_DDL.SelectedItem.Value!="ANY") 
                {
                    executeResistantListQuery_MLNO(mlno_DDL.SelectedItem.Value);
                }
            }
            if(Specific_Query_DDL.SelectedItem.Value=="NegativeL")
            {
                if(mlno_DDL.SelectedItem.Value=="ANY")
                {
                    executeNegativeListQuery_ANY();
                }
                else if(mlno_DDL.SelectedItem.Value!="ANY")
                {
                      executeNegativeListQuery_MLNO(mlno_DDL.SelectedItem.Value);
                }
            }
            
        }

Thank you all who will try to solve the problem. To me it seems that the the second dropdown list is getting refreshed everytime I am posting the page back/submit and that's why "ANY" is getting selected and thus it's pulling all the data. This is not the whole code, this is only the part I thought might be useful to suggest any solution. Though other people might feel it's useless(!).

Re: Dropdown list value is not retaining on page post back

Abhishek Sur31-Aug-09 10:36

Re: Dropdown list value is not retaining on page post back

31-Aug-09 10:36

Yes.. the culprit is your page load method..

Just for every post-back, even when submit button is clicked, ASP.NET first calles Page_Load and after its execution it calles the general event handler.

Just omit the lines

if (this.IsPostBack)
{
    if(Specific_Query_DDL.SelectedItem.Value=="ResistantL")
    {
          getMLNO(Specific_Query_DDL.SelectedItem.Value);
    }
    if(Specific_Query_DDL.SelectedItem.Value=="NegativeL")
    {
          getMLNO(Specific_Query_DDL.SelectedItem.Value);
    }
}

and place them in Listbox1_selectedIndexChanged event.

I thin as that is called specific when postback occurs on selected indexchanged event, the submit will not load the 2nd dropdown onsubmit.

The problem will be fixed then... Thumbs Up | :thumbsup:

Abhishek Sur

My Latest Articles
Create CLR objects in SQL Server 2005
C# Uncommon Keywords
Read/Write Excel using OleDB
Don't forget to click "Good Answer" if you like to.

skhan1731-Aug-09 11:09

skhan17

31-Aug-09 11:09

Thank you Mr. Sur. I knew that the culprit is the page load method.. but didn't know how to populate the second dropdown list without the pageload.

Should I put the code you mentioned exactly inside the Specific_Query_DDL_selectedIndexChanged function ? And should I call that function inside the page_Load function?

Please suggest. Thanks in advance.

Re: Dropdown list value is not retaining on page post back

Abhishek Sur31-Aug-09 11:40

Re: Dropdown list value is not retaining on page post back

31-Aug-09 11:40

No..

You dont need to call selectedIndexChanged function from page_load, it will automatically been called. Rather than that, you just write

if(IsPostBack) return;

in the page_load, to eliminate any code to be executed in page_load during postbacks.

When the selectedIndexChanged is posting back the page to the server, it always calls the Page_Load event first, then its original event handler. So you just need to suppress page_load during event calls.

Hope you got it clearly.

Abhishek Sur

My Latest Articles
Create CLR objects in SQL Server 2005
C# Uncommon Keywords
Read/Write Excel using OleDB
Don't forget to click "Good Answer" if you like to.

Christian Graus31-Aug-09 14:02

Re: Dropdown list value is not retaining on page post back

31-Aug-09 14:02

Abhishek Sur wrote:
if(IsPostBack) return;

in the page_load, to eliminate any code to be executed in page_load during postbacks.

This is nuts. It may work for the code he has today, but it's a terrible paradigm. Why should one not write code in page load that needs to run every time ? Instead, put if (!IsPostback) blocks around the specific code you need to stop running

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Abhishek Sur31-Aug-09 23:25

Re: Dropdown list value is not retaining on page post back

31-Aug-09 23:25

Actually If you saw the code above, the person is populating the Dropdown from Page_load.

Christian Graus wrote:
Why should one not write code in page load that needs to run every time

Actually your question will get you the answer. Yes of course.. If one needs to run a code every time, he could have write this before the line, or if specific to the postback he could use it just within the if block.

I think it depends upon the requirement. $Shucks | :-\$ $Shucks | :-\$

The code that he wrote doesnt require to populate dropdown during postbacks. so he should eliminate the function call during each postback as the page which is posted back already had the items in the select. Rose | [Rose]

Abhishek Sur

My Latest Articles
Create CLR objects in SQL Server 2005
C# Uncommon Keywords
Read/Write Excel using OleDB
Don't forget to click "Good Answer" if you like to.

Christian Graus31-Aug-09 14:07

Referencing HTML input boxes correctly

31-Aug-09 14:07

Yes, this is still far too much code to be posting.

You don't need to be reloading the data every time, unless you turn off viewstate. If you do need to, do it in page_prerender, that's the right place to do it anyhow. Then it will happen AFTER your event fires.

skhan17 wrote:
if(Specific_Query_DDL.SelectedItem.Value=="default")

Hard coded strings are a bad idea. can't you store an enum or something in the value ?

skhan17 wrote:
string sql= "SELECT re_MLNO,sum(re_HIV1_Status) AS hivNeg, MAX(re_SpecimenDate)- MIN(re_SpecimenDate) AS DaysSeronegative FROM ml_hiv_status GROUP BY re_MLNO";

OleDbConnection connection = new OleDbConnection(HIV.Database.DataConstants.CONNECTION_STRING);
OleDbDataAdapter adapter = new OleDbDataAdapter();
OleDbCommand command = new OleDbCommand(sql, connection);

SQL in the presentation layer is always a sign of no design. I'd fire anyone who presented code like this to me.

skhan17 wrote:
if(Specific_Query_DDL.SelectedItem.Value=="ResistantL")
{
getMLNO(Specific_Query_DDL.SelectedItem.Value);
}
if(Specific_Query_DDL.SelectedItem.Value=="NegativeL")
{
getMLNO(Specific_Query_DDL.SelectedItem.Value);
}

Hard coded strings are still bad. And, have you never heard of the || operator ?

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

dptalt31-Aug-09 5:10

dptalt

31-Aug-09 5:10

I have a user control with two input boxes. The onkeyup calls a function. The function works but the problem is when I have two of these user controls on a page. When document.getElementById("Text2").focus() executes for the second user control it puts the focus on Text2 in the first user control. How do I reference Text2 so that the focus is place on the correct Text2?

function TimeEntryHoursOnClick(theTextbox)
{
if (event.keyCode == 38)
theTextbox.value = parseFloat(theTextbox.value) + 1

if (event.keyCode == 39)
document.getElementById("Text2").focus();
}

Not Active31-Aug-09 6:44

Not Active

31-Aug-09 6:44

You need to use the ClientID to get the proper DOM element. Try looking here[^]

only two letters away from being an asset

dptalt31-Aug-09 9:15

dptalt

31-Aug-09 9:15

The code cannot find Text2.   This line returns null.   Any ideas why?

document.getElementById("ctl00_ContentPlaceHolder1_TimeEntryBox1_Text2");

Here is the HTLM.

<div id="ctl00_ContentPlaceHolder1_TimeEntryBox1_Panel1" style="border-color:#7F9DB9;border-width:1px;border-style:Solid;width:89px;">

<input id="Text1" name="Text1" onkeyup="TimeEntryHoursOnClick(this)" onblur="TimeEntryHoursOnBlur(this)" style="border: 0px none #FFFFFF; width: 12px; " type="text" maxlength="2" />

:

<input id="Text2" name="Text2" type="text" onkeyup="TimeEntryMinutesOnClick(this)" onblur="TimeEntryMinutesOnBlur(this)" style="border: 0px none #FFFFFF; width: 12px" maxlength="2" />


<input type="hidden" id="ctrlPrefix" name="ctrlPrefix" value='ctl00_ContentPlaceHolder1_TimeEntryBox1_'>


</div>

Not Active31-Aug-09 9:56

Not Active

31-Aug-09 9:56

Have you tried debugging the JavaScript?

only two letters away from being an asset

Abhishek Sur31-Aug-09 10:44

31-Aug-09 10:44

getElementById is a javascript function that finds one element. If the ID of the textbox is Text1 when rendered to the client browser (I mean if you see id of your input as Text1 when you see Source from the browser), just use

var element = document.getElementById("Text1");

rather than

var element = document.getElementById("ctl00_ContentPlaceHolder1_TimeEntryBox1_Text2");

If you want to find the div, you can do so using

var divelement = document.getElementById("ctl00_ContentPlaceHolder1_TimeEntryBox1_Panel1");

Always remember, you can mention only those elements which are rendered to the client. ASP.NET server side Ids are different than what is rendered in the client side. Use ClientID than ID for any server control to get the actual ID generated in the client, and always call this ID through JAVASCRIPT.

Hope you got it. Thumbs Up | :thumbsup:

Abhishek Sur

My Latest Articles
Create CLR objects in SQL Server 2005
C# Uncommon Keywords
Read/Write Excel using OleDB
Don't forget to click "Good Answer" if you like to.

Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

dptalt1-Sep-09 1:35

dptalt

1-Sep-09 1:35

Ok thanks for the info, but how would I set the focus to Text2 in ctl00_ContentPlaceHolder1_TimeEntryBox2_Panel1?

<div id="ctl00_ContentPlaceHolder1_TimeEntryBox1_Panel1" style="border-color:#7F9DB9;border-width:1px;border-style:Solid;width:89px;">

<input id="Text2" name="Text2" type="text" onkeyup="TimeEntryMinutesOnClick(this)" onblur="TimeEntryMinutesOnBlur(this)" style="border: 0px none #FFFFFF; width: 12px" maxlength="2" />

<input type="hidden" id="ctrlPrefix" name="ctrlPrefix" value='ctl00_ContentPlaceHolder1_TimeEntryBox1_'>
</div>

<div id="ctl00_ContentPlaceHolder1_TimeEntryBox2_Panel1" style="border-color:#7F9DB9;border-width:1px;border-style:Solid;width:89px;">

<input id="Text2" name="Text2" type="text" onkeyup="TimeEntryMinutesOnClick(this)" onblur="TimeEntryMinutesOnBlur(this)" style="border: 0px none #FFFFFF; width: 12px" maxlength="2" />

<input type="hidden" id="ctrlPrefix" name="ctrlPrefix" value='ctl00_ContentPlaceHolder1_TimeEntryBox2_'>
</div>

ncsubbu31-Aug-09 2:47

ncsubbu

31-Aug-09 2:47

Hi
I am using sqlhelper class for dataaccess.I am retriving records from view.The records more than 20,000.In this case i got timeout expired.i increase the connectiontimeout is 120sec.If any solution to solve this problem.

your's subbu

Re: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Tamer Oz31-Aug-09 2:55

Tamer Oz

31-Aug-09 2:55

Try setting commands timeout property to a higher value

Re: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Abhijit Jana31-Aug-09 3:06

Abhijit Jana

31-Aug-09 3:06

ncsubbu wrote:
The records more than 20,000.In this case i got timeout expired.

Why you are trying to retreive this much of data ? Try to use some filter criteria to minimize the records.

If you have enoung time out, check the process in backend. Where its taking time, Use Breakpoint and Debug to find it out. Or Profile your Query.

One more suggestion, please don't hit database frequently for this. It will impact your Performacne badly. Try to use caching for improve the performance !

Abhijit Jana | Codeproject MVP
Web Site : abhijitjana.net
Don't forget to click "Good Answer" on the post(s) that helped you.

Re: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Fayu31-Aug-09 6:50

Fayu

31-Aug-09 6:50

Try creating an index on the table columns. that should help increase performance.

Re: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Christian Graus31-Aug-09 14:19