How to query an Xml Document using a SP and populate an ASP DropDownList from code-behind?

Question

Given the xml:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <lfSpec1ForLoc>
        <a href="/spec.aspx?id=20" title="AI">AI</a>
    </lfSpec1ForLoc>
    <lfSpec2ForLoc />
    <lfSpec3ForLoc />
    <lfSpec4ForLoc />
    <lfSpec5ForLoc />
    <lfSpec6ForLoc />
    <lfSpec7ForLoc />
    <lfSpec8ForLoc />
    <lfSpec9ForLoc />
    <lfSpec10ForLoc />
</root>

My URL is: www.mypage.com/off.aspx?id=12

I have the following Stored Procedure:

ALTER PROCEDURE [dbo].[MySP]
(
@LstrID varchar(200), -- 12 {from the query string in the above URL}
)

AS

BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    SELECT
        CAST ([con] AS XML).query('/root/lfSpec1ForLoc/a') AS [Spec1]
        , CAST ([con] AS XML).query('/root/lfSpec2ForLoc/a') AS [Spec2]
        , CAST ([con] AS XML).query('/root/lfSpec3ForLoc/a') AS [Spec3]
        , CAST ([con] AS XML).query('/root/lfSpec4ForLoc/a') AS [Spec4]
        , CAST ([con] AS XML).query('/root/lfSpec5ForLoc/a') AS [Spec5]
        , CAST ([con] AS XML).query('/root/lfSpec6ForLoc/a') AS [Spec6]
        , CAST ([con] AS XML).query('/root/lfSpec7ForLoc/a') AS [Spec7]
        , CAST ([con] AS XML).query('/root/lfSpec8ForLoc/a') AS [Spec8]
        , CAST ([con] AS XML).query('/root/lfSpec9ForLoc/a') AS [Spec9]
        , CAST ([con] AS XML).query('/root/lfSpec10ForLoc/a') AS [Spec10]
    FROM
        [myDB1].[dbo].[con]
    WHERE
        [folder_id] = 106
        AND 
        [content_id] = '%' + Lstr + '%'
END

The result from the SP is:

Spec1                                           Spec2                                       Spec3   Spec4   Spec5   Spec6   Spec7   Spec8   Spec9   Spec10
<a href="/spe.aspx?id=1" title="AI">AI</a>      <a href="/spe.aspx?id=5" title="QW">QW</a>

I would like to populate the below dropdownlist:

<ASP:DropDownList runat="server" ID="ddl1"></ASP:DropDownList>

So the HTML output is as follow:

<SELECT>
    <option value="/spe.aspx?id=1">AI</option>
    <option value="/spe.aspx?id=5">QW</option>
</SELECT>

What is the best way to achieve the populating the dropdownlist after executing the SP?

Answer 1

I would change your PROC to make better usage of Xquery and the xml parsing capabilities of Sql Server.

What you can do from your PROC is project a table of (URL, Title) pairs from your the xml Records in your table with a query as simple as:

SELECT Nodes.node.value('(a/@href)[1]', 'varchar(100)') AS URL,
       Nodes.node.value('(a/@title)[1]', 'varchar(100)') AS Title
FROM 
(
  SELECT CAST(con.con AS XML) AS con,
    folder_id,
    content_id
    FROM con
) x
CROSS APPLY x.Con.nodes('/root/*[a]') as Nodes(node)
WHERE
[folder_id] = 106
AND 
[content_id] LIKE '%' + @LstrID + '%';

The /root/*[a] will navigate all lfSpecxForLoc nodes (irrespective of name), and filter just those with an a child element, thus avoiding the need to filter out nulls. Also, by projecting the elements as individual rows, you won't need to scrape out 10 explicit columns - there will be as many rows as there are data.

Here's a SqlFiddle of the resulting table projected by the above query.

From here, it is a simple task to pull the resultset into an ADO data reader or bind this to your drop down list (eg set the .DataSource to the data reader, and call .DataBind() on the DropDownList ).