Need detail about dropdownlist auto postback

Category: ASP.NET
23 Nov 2015 01:34
Joined: 11/06/2012
Level: Gold
Points: 767
Points: 5
Need detail about dropdownlist auto postback
Dear Friends
In my web based project i have one and i place one drop down and one text box. i was fill the drop down list with database value, now i want to get the drop down list value into textbox.

here i try with below code

<script type="text/javascript">
function GetMasterDetails() {

var value = document.getElementById('<%=ddlContractorGrade.ClientID%>');

var getvalue = value.options[value.selectedIndex].value;
var gettext = value.options[value.selectedIndex].text;
// alert("value:-" + " " + getvalue + " " + "Text:-" + " " + gettext);

document.getElementById('<%=txtTin0.ClientID%>').value = getvalue;

}
</script>

-----------------------------------------
my problem when i select the value in drop down list then
i was press the tab control, now i got the value in textbox, but the dropdown automatically postback to the drop down 0 index value.

Ex: i have 1 to 10 no in drop down. now i select 9 then press tab for move to the next control, when i was press the control that drop down get automatically postback.

can any one guide friends
#763264
23 Nov 2015 01:40
Joined: 03/05/2013
Level: Gold
Points: 15349
Points: 3

Hi NavaneethKrishnan,

If you are bind the dropdown in page load event and not is postback, obviously it is pointing 0 index for each post back, because you are binding the control again and again. If you want to maintain that selection state I request you to maintain the dropdown list index in one hidden field or any state control(viewstate) and assign that back to dropdown while binding time. This is the one of the way to maintain the selected index.
--------------------------------------------------------------------------------
Give respect to your work, Instead of trying to impress your boss.

N@veen
Blog : http://naveens-dotnet.blogspot.in/
#763268
23 Nov 2015 08:11
Joined: 13/06/2007
Level: Gold
Points: 20603

Points: 3
Check if you have set 'AutoPostback' property of the dropdownlist to 'true', then make it 'false'
In that case you need to use javascript to collect dropdown value and fill it in your textbox
see below snippet
<script language="javascript"> function setTextboxVal() { //get selected value from dropdownlist and set it in textbox document.getElementById("txtId").value = document.getElementById("dlstValue").value; } </script>
Thanks
Koolprasd2003
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]
#763285
24 Nov 2015 10:09
Joined: 11/06/2012
Level: Gold
Points: 767
Points: 1
Hi Naveen

Dear Friends
In my web based project i have one and i place one drop down and one text box. i was fill the drop down list with database value, now i want to get the drop down list value into textbox.

here i try with below code

<script type="text/javascript">
function GetMasterDetails() {

var value = document.getElementById('<%=ddlContractorGrade.ClientID%>');

var getvalue = value.options[value.selectedIndex].value;
var gettext = value.options[value.selectedIndex].text;
// alert("value:-" + " " + getvalue + " " + "Text:-" + " " + gettext);

document.getElementById('<%=txtTin0.ClientID%>').value = getvalue;

}
</script>

-----------------------------------------
my problem when i select the value in drop down list then
i was press the tab control, now i got the value in textbox, but the dropdown automatically postback to the drop down 0 index value.

Ex: i have 1 to 10 no in drop down. now i select 9 then press tab for move to the next control, when i was press the control that drop down get automatically postback.

can you give a example for your reply.....
Regards by
Navaneetha krishnan
Your idea should be improve my knowledge
#763344
26 Nov 2015 09:39
Joined: 05/06/2009
Level: Gold
Points: 10218
Points: 3
This will happen because of the postback.

1. If any control triggers the event, the page will get post back.
2. In the postback it will trigger the page load.
3. If we are binding the values in the postback, It will reset and bind the the values again. So we will lose out selected values
4. We can check the "IsPostback" in the page load. also we can use the Hidden fields to store the selected values
By Nathan
Direction is important than speed

Joined:	11/06/2012
Level:	Gold
Points:	767

Joined:	03/05/2013
Level:	Gold
Points:	15349

Joined:	13/06/2007
Level:	Gold
Points:	20603

Joined:	11/06/2012
Level:	Gold
Points:	767

Need detail about dropdownlist auto postback

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