Hi guys,
I need a bit of guidence / advice please.
Im developing a asp.net web app that sets up a number of database calls. Im working off an ORACLE 10 G XE database.
I basically want to have multiple DropDownLists where the content of each dropdown list is dependant from the selection made in the previous DropDownList.
I have my first DropDownList populated with data:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
fillDropDown1();
//fillDropDown2();
//fillDropDown3();
}
}
protected void fillDropDown1()
{
DropDownList1.DataSource = getDataSource();
DropDownList1.DataTextFiel
DropDownList1.DataValueFie
DropDownList1.DataBind();
}
protected DataSet getDataSource()
{
OleDbConnection myConn = new OleDbConnection();
myConn.ConnectionString ="Provider=oraoledb.oracle
DataSet ds = new DataSet();
OleDbDataAdapter da = new OleDbDataAdapter("select code from dept", myConn);
da.Fill(ds);
return ds;
}
How would I go about linking the DropDownLists??
As always..... Any help greatly appreciated!
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A great way to do this is to use the Ajax / Atlas mechanism. That is, instead of doing a post back, have your client side script call-back to a method in your application to retrieve the list of values when the selection is made.
This page has excellent and short tutorials on using Ajax from ASP.NET. Example #3 is exactly what you are asking for (cascading drop down controls)
http://www.asp.net/learn/v
dcgames - Thanks for the link, it was very interesting and I will use the examples in future projects however for this application I will not use AJAX I dont think.......
dstanley9: - thanks for your post.
I have populated all the DropDownLists and have have had a play around with the auto postback feature. Do you have an example of using an event handler to get the data from the previos controls and then binding it together?
As always - any help greatly appreciated
Sure. In this example I have two drop-downs: ddState and ddCounty. Here are the event handlers and binding methods:
protected void ddState_SelectedIndexChang
{
BindCounty();
}
private void BindCounty()
{
// Gets a list of counties by the state ID
// Returns a collection of objects with two properties: CountyName and CountyID
ddCounty.DataSource = QueryAgent.GetCountiesBySt
ddCounty.DataTextField = "CountyName";
ddCounty.DataValueField = "CountyID";
ddCounty.DataBind();
}
Business Accounts
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by: dstanley9Posted on 2007-02-15 at 11:20:25ID: 18543038
Set AutoPostBack to true for the drop-downs that cause a change in the other drop-downs. Then add an event handler for the SelectedIndexChanged event. In that event handler get the data for the other controls based on the selected item (either get it from the database or set a filter on the DataTable if you get all of the data at once), then re-bind the other controls (don't re-bind the control that fired the event or you'll lose your selected item index).