使用javascript将值从一个列表框移动到另一个列表框然后使用c＃读取值

Question

i have two listbox(listbox 1 and listbox2).i have used following javscript code to move value from one listbox to other.

 <script language="javascript" type="text/javascript">

function fnMoveItems(lstbxFrom,lstbxTo)
{
 var varFromBox = document.all(lstbxFrom);
 var varToBox = document.all(lstbxTo); 
 if ((varFromBox != null) && (varToBox != null)) 
 { 
  if(varFromBox.length < 1) 
  {
   alert('There are no items in the source ListBox');
   return false;
  }
  if(varFromBox.options.selectedIndex == -1) // when no Item is selected the index will be -1

  {
   alert('Please select an Item to move');
   return false;
  }
  while ( varFromBox.options.selectedIndex >= 0 ) 
  { 
   var newOption = new Option(); // Create a new instance of ListItem 

   newOption.text = varFromBox.options[varFromBox.options.selectedIndex].text; 
   newOption.value = varFromBox.options[varFromBox.options.selectedIndex].value; 
   varToBox.options[varToBox.length] = newOption; //Append the item in Target Listbox

   varFromBox.remove(varFromBox.options.selectedIndex); //Remove the item from Source Listbox 

  } 
 }
 return false; 
}
</script>

This code moves value from one listbox to another,but actually when i try to read the second listbox values, one to whhich values are copied , i am not able to read those values. when i check it shows ListBox2.Items.Count is 0

Answer 1

As Amar Palsapure stated in the comments, changes on clientside with javascript does not reflect on server side without some hacking on your part (add the values to hidden fields etc. have a look here ), so you would not be able to see the changes server side. I assume the line ListBox2.Items.Count is server side.

It would be a lot better and easier for you if you do an ajax request and do it server side within an update panel.

Answer 2

确保在页面加载时不要将列表框设置代码放在if语句中，以确保它不是回发。

Answer 3

The server side process (C) is not able to read from the client, without an HTTP request - page reload(which is probably not what you want to do). Your javascript looks good, but you probably need to use AJAX technique, which allows your client code to speak to your server code without reloading the page in the traditional HTTP request model.

Try using JQuery library to assist in setting up your request to the server. http://api.jquery.com/jQuery.ajax/

Answer 4

As TBohnen.jnr suggested I recommend using an Update Panel and then an Asynchrounous Postback Trigger to refresh the update panel. You will need to put the list boxes inside the panel and then have an event that you raise when the content is moved.