How do I return XML from a Stored Procedure?

Question

I created a Stored Procedure that returns XML and I would like to also return that XML in a method I created.

I'm having two issues. First, after doing some searching, it is not advised to use .ExecuteScalar(); because it truncates strings over 2033 characters.

So, I found a function called ExecuteXMlReader(), but in Visual Web Developer 2010 Express that runs on .NET 4.0 (C#) it is throwing the error "System.Data.SqlClient.SqlCommand' does not contain a definition for 'ExecuteXMlReader' and no extension method 'ExecuteXMlReader' accepting a first argument of type 'System.Data.SqlClient.SqlCommand' could be found"

Here is my stored procedure:

CREATE PROCEDURE dbo.GETReport
    (@ReportDate date)
AS
SELECT * FROM ReportTbl
WHERE ReportDate = @ReportDate
for xml auto, elements

set nocount on;

RETURN

Here is my method:

using System.Data;
using System.Data.SqlClient;

...

        //connect        
        SqlConnection conn = new SqlConnection("Data Source=localhost; User Id=foo; Password=foo; Initial Catalog=Database1");
        conn.Open();

        //create command
        SqlCommand cmd = new SqlCommand("dbo.GETReport", conn);
        cmd.Parameters.AddWithValue("@ReportDate", "3/24/2011"); 
        cmd.CommandType = CommandType.StoredProcedure;

        DataReader rd = cmd.ExecuteXMlReader(); //this is where error is occuring
        //also, it is throwing an error for DataReader as well saying there is no
        //type of namespace with that name
        rd.Read();

        string s = rd.ReadOuterXml(); //also dont know if this is how i should return the XML

Second, in addition to the ExecuteXMLReader() issue, I don't know if returning a string is the proper way of returning XML in the first place... Is there another object type I should convert it to?? Or another function I should use??

Thank you in advance!!

Solution 1

First, SqlCommand has a ExecuteXmlReader method, not ExecuteXMlReader as you wrote (this is misspelling). Second, SqlCommand.ExecuteXmlReader method returns a value of type XmlReader, not a DataReader as is in your example. So changing your code to:

using (XmlReader reader = cmd.ExecuteXmlReader())
{
    while(reader.Read())
    {
        string s = reader.ReadOuterXml();
        // do something with s
    }
}

should solve the issue.

Solution 2

I had trouble with the simple approach from @Alex and better luck with this approach:

// Execute a SqlCommand that you've created earlier.
// (Don't forget your 'using' statements around SqlConnection, SqlCommand and XmlReader!)
// This is where our XML will end up 
var xmlDocument = new XmlDocument();

using (XmlReader xmlReader = cmd.ExecuteXmlReader())
{
    // Now xmlReader has the XML but no root element so we can't
    // load it straight into XmlDocument :( But we can use XPathDocument
    // to add a node for us first.
    var xp = new XPathDocument(xmlReader);
    var xn = xp.CreateNavigator();
    XmlNode root = xmlDocument.CreateElement("YourFavouriteRootElementName");
    root.InnerXml = xn.OuterXml;
    xmlDocument.AppendChild(root);
}

// Now xmlDocument has all the XML you have dreamed of

Using the reader.Read() ... var s = reader.ReadOuterXml() somehow missed some of the elements in my longer more complex XML. I didn't bother investigating why but switching to XPathDocument worked for me.

Comments

[AngeloS]

that worked great, but quick question.. is there a way to return the XML as XML and not a string?

[John Saunders]

The XmlReader is the underlying way to read any XML. You would use it to load an XDocument or XmlDocument, using XDocument.Load(reader), for instance.

[Oleks]

@Angelo, you could use something similar to XmlDocument document = new XmlDocument(); document.Load(reader); or use XDocument.Load(reader) as @John mentioned. Thanks, @John!

[AngeloS]

When I use XmlReader reader = cmd.ExecuteXmlReader(); XmlDocument document = new XmlDocument(); document.Load(reader); I get the following error: "This document already has a 'DocumentElement' node." .. any ideas??