CODEWITHSUNDEEP
c#asp.netsqldatasource
finxie
finxie

Reputation: 124

Dropdownlist-hierarchy with SQLdatasource

In my ASP.NET folder i have 3 dropdownboxes who are filled with sorts of categories with 3 different SQLdatascources. Each dropdownlist depends on the one above it.
The intention of this thing is that after selecting something in dropdownlist1, the datasource in dropdownlist2 changes. So the data in dropdown2 depend on the selected value in dropdown1. And the data in dropdown3 depend on the selected value in dropdown2.
It all works nice and dandy a first time. But when I selected a value in dd1 and after this a value in dd2, it starts to fail.
When I change the value a second time in dropdown1 for example, the other dropdownlists don't alter.

Thx in advance for replies

Upvotes: 2

Views: 916

Answers (3)

Pieter Temmerman
Pieter Temmerman

Reputation: 16

Example of code with 2 different tables connected by keys, in this example: companyID.

public partial class Default : Page
{
    public void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            var datacontext = new DataClasses1DataContext();
            List<Company> companies = datacontext.Companies.ToList();
            DropDownList1.DataSource = companies;
            DropDownList1.DataValueField = "CompanyID";
            DropDownList1.DataTextField = "CompanyName";
            DropDownList1.DataBind();
        }
    }

    public void DropDownList1SelectedIndexChanged(object sender, EventArgs e)
    {
        using (var dc = new DataClasses1DataContext())
        {
            DetailsView2.DataSource = null;
            DetailsView2.DataBind();

            DetailsView1.DataSource = dc.Companies.Where(d => d.CompanyID.Equals(DropDownList1.SelectedValue)).ToList();
            DetailsView1.DataBind();

            List<Contact> contacts = 
            dc.Contacts.Where(d => d.CompanyID.Equals(DropDownList1.SelectedValue)).ToList();            
            DropDownList2.DataSource = contacts;
            DropDownList2.DataTextField = "LastName";
            DropDownList2.DataValueField = "ContactID";
            DropDownList2.DataBind();

            if (contacts.Any())
            {
                DetailsView2.DataSource = dc.Contacts.Where(c => c.ContactID.Equals(DropDownList2.SelectedValue)).ToList();
                DetailsView2.DataBind();
            }

        }
    }

    public void DropDownList2SelectedIndexChanged(object sender, EventArgs e)
    {
        using (var dc = new DataClasses1DataContext())
        {
            DetailsView2.DataSource = dc.Contacts.Where(c => c.ContactID.Equals(DropDownList2.SelectedValue)).ToList();
            DetailsView2.DataBind();
        }
    }
}

Upvotes: 0

Schoof
Schoof

Reputation: 2855

Put the code to fill dd2 in the OnSelectedIndexChanged of dd1, and do the same for the OnSelectedIndexChanged of dd2 (to fill dd3).

Upvotes: 0

Mikey Mouse
Mikey Mouse

Reputation: 3098

To do this kind of thing, you need to make sure your top level drop down list is only populated once, so put it in the page load with a !isPostback around it. Then attach a OnSelectedIndexChanged() event on that top level dropdownlist, and in it, be sure to clear the items in the second level dropdown list before setting it's new datasource.

Then a OnSelectedIndexChanged() on the second level dropdown list, and be sure to clear the third before populating it.

Then the third doesn't need any events.

Upvotes: 4

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