Tài liệu Converting a DataSet to an ADO Recordset docx

Solution You must persist the DataSet to XML, transform it to ADO Recordset schema, and load it into an ADO Recordset using COM interop.. The sample uses one XML file: Orders.xslt The

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Recipe 5.10 Converting a DataSet to an ADO Recordset

Problem

You need to convert a DataSet to an ADO Recordset so that you can use it in a legacy application

Solution

You must persist the DataSet to XML, transform it to ADO Recordset schema, and load

it into an ADO Recordset using COM interop

You'll need a reference to the Primary Interop Assembly (PIA) for ADO provided in the

file ADODB.DLL Select adodb from the NET tab in Visual Studio NET's Add

Reference Dialog

The sample uses one XML file:

Orders.xslt

The XSLT stylesheet used to transform the XML document output by the DataSet into an ADO Recordset XML document

The sample code contains one event handler and one method:

Go Button.Click

Converts the DataSet to an ADO Recordset using the following steps:

1 A shell XML document for the ADO Recordset is created

2 A DataReader accesses the schema information for the data to convert using the GetSchemaTable( ) method This information is mapped to and added to the ADO Recordset XML document

3 The DataSet is loaded with data for a single DataTable The XML

document for the DataSet is transformed and written into the ADO Recordset XML document

4 An ADO Recordset object is created and loaded with the ADO Recordset XML document This completes the conversion

5 The ADO Recordset is loaded into a DataTable using the

OleDbDataAdapter The default view for the table is bound to the data grid

on the form to display the results of the conversion

GetDataTypeInfo( )

This method maps SQL Server specific types to data type attributes for the ds and

rs namespaces used to serialize an ADO Rowset

The XSLT file is shown in Example 5-10

Example 5-10 File: Orders.xslt

<?xml version="1.0" ?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

xmlns:rs="urn:schemas-microsoft-com:rowset"

xmlns:z="#RowsetSchema"

xmlns:msxsl="urn:schemas-microsoft-com:xslt"

xmlns:wxh="http://element14.com/wxhnamespace"

version="1.0">

<msxsl:script language="CSharp" implements-prefix="wxh">

<![CDATA[

private String GetShortTime(String longDateTime)

{

return longDateTime.Substring(0,19);

}

]]>

</msxsl:script>

<xsl:output method="xml" indent="yes" />

<xsl:template match="NewDataSet">

<rs:data>

<xsl:apply-templates select="Orders" />

</rs:data>

</xsl:template>

<xsl:template match="Orders">

<z:row>

<xsl:apply-templates select="@OrderID" />

<xsl:apply-templates select="@CustomerID" />

<xsl:apply-templates select="@EmployeeID" />

<xsl:apply-templates select="@OrderDate" />

<xsl:apply-templates select="@RequiredDate" />

<xsl:apply-templates select="@ShippedDate" />

<xsl:apply-templates select="@ShipVia" />

<xsl:apply-templates select="@Freight" />

<xsl:apply-templates select="@ShipName" />

<xsl:apply-templates select="@ShipAddress" />

<xsl:apply-templates select="@ShipCity" />

<xsl:apply-templates select="@ShipRegion" />

<xsl:apply-templates select="@ShipPostalCode" /> <xsl:apply-templates select="@ShipCountry" />

</z:row>

</xsl:template>

<xsl:template match="@OrderDate">

<xsl:attribute name="OrderDate">

<xsl:value-of select="wxh:GetShortTime(.)" />

</xsl:attribute>

</xsl:template>

<xsl:template match="@RequiredDate">

<xsl:attribute name="RequiredDate">

<xsl:value-of select="wxh:GetShortTime(.)" />

</xsl:attribute>

</xsl:template>

<xsl:template match="@ShippedDate">

<xsl:attribute name="ShippedDate">

<xsl:value-of select="wxh:GetShortTime(.)" />

</xsl:attribute>

</xsl:template>

<xsl:template match="@*">

<xsl:copy-of select="." />

</xsl:template>

</xsl:stylesheet>

The C# code is shown in Example 5-11

Example 5-11 File: ConvertDataSetToAdoRecordsetForm.cs

// Namespaces, variables, and constants

using System;

using System.Configuration;

using System.Windows.Forms;

using System.IO;

using System.Text;

using System.Xml;

using System.Xml.Xsl;

using System.Data;

using System.Data.SqlClient;

using System.Data.OleDb;

private const String ADOXMLFILE =

ConfigurationSettings.AppSettings["Temp_Directory"] + "ADO_Orders.xml"; //

private void goButton_Click(object sender, System.EventArgs e)

{

Cursor.Current = Cursors.WaitCursor;

String sqlText = "SELECT * FROM Orders";

// Create the connection

SqlConnection conn = new SqlConnection(

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

// Create the command to load all orders records

SqlCommand cmd = new SqlCommand(sqlText, conn);

conn.Open( );

// Create a DataReader from the command

SqlDataReader dr = cmd.ExecuteReader(

CommandBehavior.SchemaOnly | CommandBehavior.KeyInfo);

// Create a table of the schema for the DataReader

DataTable schemaTable = dr.GetSchemaTable( );

// Create an XML document

XmlDocument xmlDoc = new XmlDocument( );

// Add ADO namespace and schema definition tags to the XML document

String adoXml =

"<xml xmlns:s = 'uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882' " + "xmlns:dt = 'uuid:C2F41010-65B3-11d1-A29F-00AA00C14882' " +

"xmlns:rs = 'urn:schemas-microsoft-com:rowset' " +

"xmlns:z = '#RowsetSchema'>" +

"<s:Schema id = 'RowsetSchema'>" +

"<s:ElementType name = 'row' content = 'eltOnly'>" +

"</s:ElementType>" +

"</s:Schema>" +

"</xml>";

xmlDoc.LoadXml(adoXml);

// Create a namespace manager for the XML document

XmlNamespaceManager nm = new XmlNamespaceManager(xmlDoc.NameTable); // Add ADO prefixes

nm.AddNamespace("s", "uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882"); nm.AddNamespace("dt", "uuid:C2F41010-65B3-11d1-A29F-00AA00C14882"); nm.AddNamespace("rs", "urn:schemas-microsoft-com:rowset");

nm.AddNamespace("z", "#RowsetSchema");

// Select the s:ElementType node

XmlNode curNode = xmlDoc.SelectSingleNode("//s:ElementType", nm);

XmlElement xe = null;

XmlAttribute xa = null;

// Iterate through the schema records for the DataReader

foreach(DataRow sr in schemaTable.Rows)

{

// Create an 'AttributeType' element for the schema record

xe = xmlDoc.CreateElement("s", "AttributeType",

"uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882");

// Get the data type

SqlDbType sqlDbType = (SqlDbType)sr["ProviderType"];

// Create the 'name' attribute

xa = xmlDoc.CreateAttribute("", "name", "");

xa.Value = sr["ColumnName"].ToString( );

xe.SetAttributeNode(xa);

// Create the 'number' attribute

xa = xmlDoc.CreateAttribute("rs", "number",

"urn:schemas-microsoft-com:rowset");

xa.Value = ((int)sr["ColumnOrdinal"] + 1).ToString( );

xe.SetAttributeNode(xa);

// Add attribute if null values are allowed in the column

if((bool)sr["AllowDBNull"])

{

xa = xmlDoc.CreateAttribute("rs", "nullable",

"urn:schemas-microsoft-com:rowset");

xa.Value = sr["AllowDBNull"].ToString().ToLower( );

xe.SetAttributeNode(xa);

}

// Add 'writeunknown' attribute

xa = xmlDoc.CreateAttribute("rs", "writeunknown",

"urn:schemas-microsoft-com:rowset");

xa.Value = "true";

xe.SetAttributeNode(xa);

// Create a 'datatype' element for the column within the

// 'AttributeType'

XmlElement dataele = xmlDoc.CreateElement("s", "datatype", "uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882"); String typeName, dbTypeName;

GetDataTypeInfo(sqlDbType, out typeName, out dbTypeName);

// Add a 'type' attribute specifying the data type

xa = xmlDoc.CreateAttribute("dt", "type",

"uuid:C2F41010-65B3-11d1-A29F-00AA00C14882");

xa.Value = typeName;

dataele.SetAttributeNode(xa);

// Add a 'dbtype' attribute, if necessary

if (dbTypeName != "")

{

xa = xmlDoc.CreateAttribute("rs", "dbtype",

"urn:schemas-microsoft-com:rowset");

xa.Value = dbTypeName;

dataele.SetAttributeNode(xa);

}

// Add the 'maxlength' attribute

xa = xmlDoc.CreateAttribute("dt", "maxLength",

"uuid:C2F41010-65B3-11d1-A29F-00AA00C14882");

xa.Value = sr["ColumnSize"].ToString( );

dataele.SetAttributeNode(xa);

// Add 'scale' and 'precision' attributes, if appropriate

if(sr["DataType"].ToString( ) != "System.String")

{

if(Convert.ToByte(sr["NumericScale"]) != 255)

{

xa = xmlDoc.CreateAttribute("rs", "scale",

"urn:schemas-microsoft-com:rowset");

xa.Value = sr["NumericScale"].ToString( );

dataele.SetAttributeNode(xa);

}

xa = xmlDoc.CreateAttribute("rs", "precision",

"urn:schemas-microsoft-com:rowset");

xa.Value = sr["NumericPrecision"].ToString( );

dataele.SetAttributeNode(xa);

}

// Add a 'fixedlength' attribute, if appropriate

if (sqlDbType != SqlDbType.VarChar &&

sqlDbType != SqlDbType.NVarChar)

{

xa = xmlDoc.CreateAttribute("rs", "fixedlength",

"urn:schemas-microsoft-com:rowset");

xa.Value = "true";

dataele.SetAttributeNode(xa);

}

// Add a 'maybe' null attribute, if appropriate

if(!(bool)sr["AllowDBNull"])

{

xa = xmlDoc.CreateAttribute("rs", "maybenull",

"urn:schemas-microsoft-com:rowset");

xa.Value = sr["AllowDBNull"].ToString().ToLower( ); dataele.SetAttributeNode(xa);

}

// Add the 'datatype' element to the 'AttributeType'

xe.AppendChild(dataele);

// Add the 'AttributeType' element to the 'ElementType' // attribute

curNode.AppendChild(xe);

}

// Add the 'extends' element with attribute 'type" of 'rs:rowbase'

xe = xmlDoc.CreateElement("s", "extends",

"uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882");

xa = xmlDoc.CreateAttribute("", "type", "");

xa.Value = "rs:rowbase";

xe.SetAttributeNode(xa);

curNode.AppendChild(xe);

// Close the reader and connection

dr.Close( );

conn.Close( );

// Load the Orders data into a table in a DataSet

DataSet ds = new DataSet( );

SqlDataAdapter da = new SqlDataAdapter(sqlText,

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

da.Fill(ds, "Orders");

// Write the column data as attributes

foreach(DataColumn dc in ds.Tables["Orders"].Columns)

dc.ColumnMapping = MappingType.Attribute;

// Write the DataSet to an XML document

XmlDataDocument ordersXml = new XmlDataDocument(ds);

// Load the XML transformation

XslTransform xslt = new XslTransform( );

xslt.Load(ConfigurationSettings.AppSettings["Project_Directory"] + @"Chapter 05\Orders.xslt");

// Transform the XML document

XmlReader xr = xslt.Transform(ordersXml, null, (XmlResolver)null);

// Load the transformed document into an XML document

XmlDocument resultXmlDoc = new XmlDocument( );

resultXmlDoc.Load(xr);

xr.Close( );

StringBuilder sb = new StringBuilder(xmlDoc.OuterXml);

// Insert the data before the closing </xml> tag

sb.Insert(sb.Length - 6, resultXmlDoc.InnerXml.Remove(8,

resultXmlDoc.InnerXml.IndexOf(">") - 8));

// Make the <z:row> elements self closing

// (ADO import doesn't work otherwise)

sb.Replace("></z:row>","/>");

// Write the order data to a file as ADO XML format

StreamWriter sw = new StreamWriter(ADOXMLFILE);

sw.Write(sb.ToString( ));

sw.Close( );

// Create and open an ADO connection

ADODB.Connection adoConn = new ADODB.Connection( );

adoConn.Open("Provider = SQLOLEDB;Data Source=(local);" + "Initial Catalog=northwind", "sa", "", 0);

// Create the ADO recordset

ADODB.Recordset rs = new ADODB.Recordset( );

try

{

// Load the XML into the ADO recordset

rs.Open(ADOXMLFILE,

adoConn,

ADODB.CursorTypeEnum.adOpenStatic,

ADODB.LockTypeEnum.adLockBatchOptimistic,

(int)ADODB.CommandTypeEnum.adCmdFile);

}

catch (System.Exception ex)

{

MessageBox.Show(ex.Message);

adoConn.Close( );

Cursor.Current = Cursors.Default;

return;

}

try

{

// Load the ADO recordset into a DataTable

OleDbDataAdapter oleDa = new OleDbDataAdapter( );

DataTable dt = new DataTable("Orders");

oleDa.Fill(dt, rs);

// Bind the default view of the table to the grid

dataGrid.DataSource = dt.DefaultView;

}

catch(Exception ex)

{

MessageBox.Show(ex.Message);

}

finally

{

adoConn.Close( );

Cursor.Current = Cursors.Default;

}

dataGrid.CaptionText = "ADO Recordset Serialized as an XML document"; }

private void GetDataTypeInfo(SqlDbType sqlDbType, out String type,

out String dbtype)

{

type = "";

dbtype = "";

// Convert the SqlDbType to type attributes in the dt and rs namespaces switch(sqlDbType)

{

case SqlDbType.BigInt:

type = "i8";

break;

case SqlDbType.Binary:

type = "bin.hex";

break;

case SqlDbType.Bit:

type = "Boolean";

break;

case SqlDbType.Char:

type = "string";

dbtype = "str";

break;

case SqlDbType.DateTime:

type = "dateTime";

dbtype = "variantdate";

break;

case SqlDbType.Decimal:

type = "number";

dbtype = "decimal";

break;

case SqlDbType.Float:

type = "float";

break;

case SqlDbType.Image:

type = "bin.hex";

break;

case SqlDbType.Int:

type = "int";

break;

case SqlDbType.Money:

type = "i8";

dbtype = "currency";

break;

case SqlDbType.NChar:

type = "string";