SQL XML Column Values (ADO.NET)

SQL Server 2005 supports the new xml data type, and developers can retrieve result sets including this type using standard behavior of the SqlCommand class. An xml column can be retrieved just as any column is retrieved (into a SqlDataReader, for example) but if you want to work with the content of the column as XML, you must use an XmlReader.

Example

The following console application selects two rows, each containing an xml column, from the Sales.Store table in the AdventureWorks database to a SqlDataReader instance. For each row, the value of the xml column is read using the GetSqlXml method of SqlDataReader. The value is stored in an XmlReader. Note that you must use GetSqlXml rather than the GetValue method if you want to set the contents to a SqlXml variable; GetValue returns the value of the xml column as a string.

' Example assumes the following directives:
'    Imports System.Data.SqlClient
'    Imports System.Xml
'    Imports System.Data.SqlTypes

Private Sub GetXmlData(ByVal connectionString As String)
    Using connection As SqlConnection = New SqlConnection(connectionString)
        connection.Open()

        'The query includes two specific customers for simplicity's 
        'sake. A more realistic approach would use a parameter
        'for the CustomerID criteria. The example selects two rows
        'in order to demonstrate reading first from one row to 
        'another, then from one node to another within the xml
        'column.
        Dim commandText As String = _
         "SELECT Demographics from Sales.Store WHERE " & _
         "CustomerID = 3 OR CustomerID = 4"

        Dim commandSales As New SqlCommand(commandText, connection)

        Dim salesReaderData As SqlDataReader = commandSales.ExecuteReader()

        ' Multiple rows are returned by the SELECT, so each row
        ' is read and an XmlReader (an xml data type) is set to the 
        ' value of its first (and only) column.
        Dim countRow As Integer = 1
        While salesReaderData.Read()
            ' Must use GetSqlXml here to get a SqlXml type. 
            ' GetValue returns a string instead of SqlXml.
            Dim salesXML As SqlXml = _
             salesReaderData.GetSqlXml(0)
            Dim salesReaderXml As XmlReader = salesXML.CreateReader()

            Console.WriteLine("-----Row " & countRow & "-----")

            ' Move to the root.
            salesReaderXml.MoveToContent()

            ' We know each node type is either Element or Text.
            ' All elements within the root are string values. 
            ' For this simple example, no elements
            ' are empty.
            While salesReaderXml.Read()
                If salesReaderXml.NodeType = XmlNodeType.Element Then
                    Dim elementLocalName As String = _
                     salesReaderXml.LocalName
                    salesReaderXml.Read()
                    Console.WriteLine(elementLocalName & ": " & _
                     salesReaderXml.Value)
                End If
            End While
            countRow = countRow + 1
        End While
    End Using
End Sub

// Example assumes the following directives:
//     using System.Data.SqlClient;
//     using System.Xml;
//     using System.Data.SqlTypes;

static void GetXmlData(string connectionString)
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();

        // The query includes two specific customers for simplicity's 
        // sake. A more realistic approach would use a parameter
        // for the CustomerID criteria. The example selects two rows
        // in order to demonstrate reading first from one row to 
        // another, then from one node to another within the xml column.
        string commandText =
            "SELECT Demographics from Sales.Store WHERE " +
            "CustomerID = 3 OR CustomerID = 4";

        SqlCommand commandSales = new SqlCommand(commandText, connection);

        SqlDataReader salesReaderData = commandSales.ExecuteReader();

        //  Multiple rows are returned by the SELECT, so each row
        //  is read and an XmlReader (an xml data type) is set to the 
        //  value of its first (and only) column. 
        int countRow = 1;
        while (salesReaderData.Read())
        //  Must use GetSqlXml here to get a SqlXml type. 
        //  GetValue returns a string instead of SqlXml. 
        {
            SqlXml salesXML =
                salesReaderData.GetSqlXml(0);
            XmlReader salesReaderXml = salesXML.CreateReader();
            Console.WriteLine("-----Row " + countRow + "-----");

            //  Move to the root. 
            salesReaderXml.MoveToContent();

            //  We know each node type is either Element or Text.
            //  All elements within the root are string values. 
            //  For this simple example, no elements are empty. 
            while (salesReaderXml.Read())
            {
                if (salesReaderXml.NodeType == XmlNodeType.Element)
                {
                    string elementLocalName =
                        salesReaderXml.LocalName;
                    salesReaderXml.Read();
                    Console.WriteLine(elementLocalName + ": " +
                        salesReaderXml.Value);
                }
            }
            countRow = countRow + 1;
        }
    }
}

See Also

Reference

SqlXml

Concepts

XML Data in SQL Server (ADO.NET)

Other Resources

ADO.NET Managed Providers and DataSet Developer Center