CODEWITHSUNDEEP
c#asp.netdrop-down-menu
Oshrib
Oshrib

Reputation: 1900

Dropdownlist first value display "choose"

I want that my dropdownlist display first value: "-choose car-"

I succeed at this way:

protected void ddl1_DataBound(object sender, EventArgs e)  
{
    Convert.ToInt32(ddl1.SelectedValue); 
    ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-"  )); 
}

and that's ok,the "-choose-" is in the first place but the problem now is that if I have values,for example,the dropdownlist show like that:

-Choose car-
Subaro
Fiat
Honda

The first value that display when I'm enter to the site is the Subaro,and to see the -choose car- the user need to open the dropdownlist and then he will see the -choose car- at the first place.How can I do that from the start,from the page load - the -choose car- will display at the ddl from the page load.Where I wrong at the code ?

I tried the itemlist with AppendDataBoundItems = "true" but I got an error, and when I succeed,the problem is the same like I said before.

Upvotes: 2

Views: 30929

Answers (4)

Ahmed Magdy
Ahmed Magdy

Reputation: 6050

  1. Make sure that you bind the data source and insert you "-choose care-" item first before selected he first item

  2. make sure when you insert your 1st item "-Choose car-" you make it once not on each PostBack. Check if not IsPostBack to add the 1st item. EDIT: Example:

    protected void Page_Load(object sender, EventArgs e)
{
   if(!IsPostBack)
   {
      ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-"  ));
   }

    ddl1.SelectedIndex = 0;
}

Upvotes: 3

Roman
Roman

Reputation: 20256

You were on the right track with using the AppendDataBoundItems property, it should be set to true if you're databinding the list.

Your markup should look like this

<asp:DropDownList runat="server" ID="ddl1" AppendDataBoundItems="true">
    <asp:ListItem Text="-Choose car-" />
</asp:DropDownList>

and your code behind probably already looks something like this

ddl1.DataSource = [your datasource goes here];
ddl1.DataBind();

This will place the Choose car text as the first option in the drop-down list and append the rest of the options below it.

Now for the more interesting part of why you were seeing the behavior you were seeing (first item not being selected). If you look at the implementation of SelectedIndex using a tool like JustDecompile (not affiliated with Telerik, just happen to use their tool) you'll see code that looks like this:

public int SelectedIndex
{
    get
    {
        int num = 0;
        num++;
        while (num < this.Items.Count)
        {
            if (this.Items[num].Selected)
            {
                return num;
            }
        }
        return -1;
    }
    set
    {
        // stuff you don't care about

        this.ClearSelection();
        if (value >= 0)
        {
            this.Items[value].Selected = true;
        }

        // more stuff you don't care about
    }
}

As you can see, the index isn't stored anywhere, it's computed every time based on which item has the Selected property set to true. When you set the SelectedIndex to 0 in the markup and databind your datasource, it will select the 0th item in that list, in your case Subaro. When you insert a new item at the beginning of the list, Subaro is still marked as the selected item, which is why when the page loads, you see that selected and not Choose car. If you want to mark Choose car as the selected item using code, you will have to do it after you data databind your dropdown. Please note, this is just an implementation detail of how DropdownList works. It could change in future version of ASP.NET so do not write code that relies on it working this way.

Upvotes: 5

Anyname Donotcare
Anyname Donotcare

Reputation: 11423

        private void FillCar()
        {      
            DataTable dt = GetCar();
            ddl1.Items.Clear();
            ddl1.DataSource = dt;
            ddl1.DataTextField = "carName"; // field name in the database
            ddl1.DataValueField = "CarNum"; // field name in the database
            ddl1.DataBind();
            ListItem li = new ListItem();
            li.Text = "--Choose car--";
            li.Value = "-1";
            ddl1.Items.Insert(0, li);
            ddl1.SelectedIndex = 0;
        }

I use method like this and call it in the page load in if (!IsPostBack){}.

Upvotes: 0

Vale
Vale

Reputation: 3298

You should do ddl1.Items.Insert(0, new ListItem("-Choose car-", "-Choose car-")); first, and than ddl1.SelectedIndex = 0

Upvotes: 1

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