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asp.net dynamic drop down

Posted on 2011-09-22
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Last Modified: 2012-05-12
Experts,

I have a dropdown <select><option value=1>1</option><option value=25>25</option></select>
When Onchange event is on, I would like to show like
City/State: <div><input name=city> <input name=state></div>

If 1 is selected, it show one city/state, if 25 is selected it show 25 city/state
and each <input name> has to be different.

And once the button is clicked, it will captures each city/state and save into the database.

Thanks
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Question by:Webboy2008
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8 Comments
 
LVL 28

Expert Comment

by:strickdd
ID: 36581036
I would do this through javascript, create an onChange javascript event for your drop down and do something like this:

function DDLChange()
{
     if(document.getElementById('<%= MyDDL.ClientID %>').val == 1)
          document.getElementById('<%= MyCity.ClientID %>').style.display = "none";
     else
          document.getElementById('<%= MyCity.ClientID %>').style.display = "";        
}
0
 

Author Comment

by:Webboy2008
ID: 36582016
strickdd: I think yours won't work to me. It just display <div> or not.
I need a list of city/state based on the number he/she select
Plus I need to save the value into Db as well.

Thanks
0
 
LVL 28

Expert Comment

by:strickdd
ID: 36582142
Then you can have you OnChange server event dynamically add the controls you need to a place holder. In that you can check the value and add the controls needed. The catch is, you will have to add these controls EVERY postback otherwise they will be lost. You can even have a method like this instead of you OnChange method:

protected void Page_Load(...)
{
      if(Page.IsPostBack)
            CreateFields();
}

private void CreateFields()
{

     if(myDDL.SelectedValue == "1")
     {
           TextBox stateTextBox = new TextBox();
           stateTextBox.ID = "MyTextBoxID" //This must be the same each postback
           //Viewstate will automatically re-populate the textboxes when created like this
          MyPlaceHolder.Controls.Add(stateTextBox);
      }
}
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LVL 28

Expert Comment

by:strickdd
ID: 36582148
If you go that route, you will need to set the AutoPostBack to true on the DDL so it does a server post.
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Author Comment

by:Webboy2008
ID: 36583653
Strickdd: If you don't mind, I really need completed working codes. Thanks. About your codes,
it won't work because it is static textbox name. If I have 25 city/states, what the textbox names will be...?
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LVL 28

Accepted Solution

by:
strickdd earned 500 total points
ID: 36586413
Assuming you have a fixed naming pattern for you drop downs, you can do something like the following. It is an example of what you will need to do, but the basic concept is to loop through your drop downs, check the values, and add the controls needed.

for (int i=0; i< numDDLs; i++)
{
        if(((DropDownList)Page.FindControl("MyDDL_ID_" + i.ToString()).SelectedValue == "1") //Instead of Page.FindControl, use the closes parrent for better efficiency
        {
                 TextBox stateTextBox = new TextBox();
                 stateTextBox.ID = "MyTextBoxID" + i.ToString() //This must be the same each postback, the static string and "i" value will make it the same
               ((PlaceHolder)Page.FindControl("MyCityStatePlaceHolder_ID_" + i.ToString().Controls.Add(stateTextBox);
         }
}

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Author Comment

by:Webboy2008
ID: 36588374
A completed and working codes will be really helpful....:-D Thanks.
0
 
LVL 28

Expert Comment

by:strickdd
ID: 36589305
Given your loosely defined requirements and no knowledge of what your setup is exactly, that is an impossible task. Given the level of knowledge you appear to have, it is well within your ability to take the code provided and make it suit your exact needs.

Experts Exchange is not a place to have people do the work for you, but rather a place to receive assistance on technical problems you are having.
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