Recipe 8.5 Reading XML Data Directly from SQL Server

Problem

You need to read XML data directly from the SQL Server.

Solution

Use the FOR XML clause in the stored procedure or SQL statement.

The C# code is shown in Example 8-8.

Example 8-8. File: ReadXmlDirectForm.cs

// Namespaces, variables, and constants
using System;
using System.Configuration;
using System.Xml;
using System.Data;
using System.Data.SqlClient;

//  . . . 

// Select statement to read XML directly.
String sqlText = "SELECT * FROM Orders FOR XML AUTO, XMLDATA";

// Create the connection.
SqlConnection conn = new SqlConnection(
    ConfigurationSettings.AppSettings["Sql_ConnectString"]);
conn.Open( );
// Create the command.
SqlCommand cmd = new SqlCommand(sqlText, conn);

// Read the XML data into a XML reader.
XmlReader xr = cmd.ExecuteXmlReader( );

// Read the data from the XML reader into the DataSet.
DataSet ds = new DataSet( );
ds.ReadXml(xr, XmlReadMode.Fragment);
xr.Close( );
conn.Close( );

xmlTextBox.Text = ds.GetXml( );

Discussion

SQL Server 2000 introduced support for retrieving data in XML format using the FOR XML clause. The .NET SQL Server data provider SqlCommand object has an ExecuteXmlReader( ) that allows you to retrieve an XML stream directly from SQL Server, where it returns an XmlReader that contains the results of the SQL query. The ExecuteXmlReader( ) method can only be used with SQL statements that return XML data, such as those with a FOR XML clause. The ExecuteXmlReader( ) method can also be used to return ntext data containing valid XML.

For more information about the FOR XML clause, see Microsoft SQL Server Books Online.