More Visual Studio Data Binding and Web Services

© 2012 University of Greenwich 1

Web Services

More Visual StudioData Binding and Web Services

Dr Kevin McManushttp://staffweb.cms.gre.ac.uk/~mk05/web/dotnet/#lecture3


Web Services

Data Binding

• Data binding in .NET is much improved on previous Microsoft implementations

• Use data binding to make a link between the user interface and the data model

• Create a C# Web Site project

• Bind a property and a method to GUI components• DataBind()


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Data Binding

add a calendar, three buttons and a label to

the design surface


Web Services

Data Binding

add a level 1 header

give the components sensible names and values - this can be

done using the property browser in design view

add some executable code to the header, calendar and label


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Data Binding

<body> <h1>Airline: <%# airline %></h1> <form id="form1" runat="server"> <div> <asp:Calendar ID="calDepart" runat="server"

SelectedDate="<%# setCalendar() %>"></asp:Calendar> <br /> </div> <asp:Button ID="btnToday" runat="server" Text="Today" /> <asp:Button ID="btnTomorrow" runat="server" Text="Tomorrow" /> <asp:Button ID="btnNextWeek" runat="server" Text="Next Week" /><br /> <br /> <asp:Label ID="lblDepartDate" runat="server" Text="Departure date">

<%# calDepart.SelectedDate.ToShortDateString() %></asp:Label>

</form></body> add code to the code behind module to handle all this

double click the GUI widgets to get the event handlers

property

methods


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Data Binding

protected int futureDay = 0;

public string airline{

get{

return "Acme Airways";}

}

public DateTime setCalendar(){

return DateTime.Today.AddDays(futureDay);}

private void Page_Load(object sender, System.EventArgs e){

DataBind();}

long winded property constructor

method to set the calendar

data bind the page on load


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Data Bindingprivate void btnToday_Click(object sender, System.EventArgs e){

futureDay = 0;DataBind();

}

private void btnTomorrow_Click(object sender, System.EventArgs e){


}

private void btnNextWeek_Click(object sender, System.EventArgs e){


}

private void calDepart_SelectionChanged(object sender, System.EventArgs e){

lblDepartDate.DataBind();}

data bind everything


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Data Binding

couldn't resist correcting the markup for this form

gotta have a green bar from the W3

note how this is all postback driven

every mouse click fires an HTTP request


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Connecting to Databases

• Visual Studio integrates with SQL Server• edit SQL Server data directly in VS.NET

• execute SQL statements

• VS Server Explorer provides easy connection to databases

View -> Server Explorer

• Data binding links controls on the user interface to data stored in SQL Server• now largely automated in VS05


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Binding to a Datagrid

• Create a new C# Web Application project• give it a meaningful name• give the web form a meaningful name

• Use the Server Explorer to locate your SQL Server database• sql-server.cms.gre.ac.uk


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• Create a new C# Web Application project• give it a meaningful name• give the web form a

meaningful name

• Use the Server Explorer to locate your SQL Server database• sql-server.cms.gre.ac.uk


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drag a table onto the design

surface

automatically creates a datagrid and invites

you to configure it


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choose from some imaginatively named

preset styles

configure what you want in the grid


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Telephone Directory

• In ye olden days you had to do a lot of this stuff

manually

• dive in and data bind stuff

• All now tooled up and automated

• Repeat the exercise as a Web Service

• Right click the project in the solution explorer

and add a web service

• rename it phoneBook.asmx


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Add a web service to the project

Telephone Directory Web Service

Give it a sensible name


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Telephone Directory Web Serviceusing System.Data;using System.Data.SqlClient;

[WebMethod] public DataSet getDirectorySql() { // Open a connection the the SQL Server SqlConnection sqlConn = new SqlConnection(); sqlConn.ConnectionString = "server=sql-server;integrated security=SSPI;database=mk05";

// Create a SQL query SqlCommand sqlCmd = sqlConn.CreateCommand(); sqlCmd.CommandType = CommandType.Text; sqlCmd.CommandText = "SELECT fname, sname, phone, loc FROM phoneBook";

// Set up data adapter and fill the dataset SqlDataAdapter dataAdptr = new SqlDataAdapter(); dataAdptr.SelectCommand = sqlCmd; DataSet dsStaff = new DataSet("directory"); dataAdptr.Fill(dsStaff, "staff");

// And return it to the client return dsStaff; }

connection string provided by our sysops

add data handling system libraries


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the DataSet is returned in XML format

with schema included


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.NET XML Containers

• Three XML document stores each with different features

• XmlDocument• the primary document store

• supports W3C standards for XML document (DOM), plus useful additional features that make it easier to access the contents

• XmlDataDocument• provides a bridge between XML and relational data by allowing the

content to be accessed as a DataSet instance as well as a standard XML document

• XPathDocument. • fast and efficient document store designed to be accessed only using

XPath methods and the XPathNavigator

• XPathNavigator can be used over any of the three document stores


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• Re-write the web service to return an XmlDocument• instead of a data set

• Convert the data set read from SQL Server into a string

• Load the string into an XmlDocument

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Telephone Directory Web Serviceusing System.Xml;

[WebMethod] public XmlDocument getDirectoryDom() { // Open a connection the the SQL Server SqlConnection sqlConn = new SqlConnection(); sqlConn.ConnectionString = "server=sql-server;integrated security=SSPI;database=mk05";

// Create a SQL query SqlCommand sqlCmd = sqlConn.CreateCommand(); sqlCmd.CommandType = CommandType.Text; sqlCmd.CommandText = "SELECT fname, sname, phone, loc FROM phoneBook";

// Set up data adapter and fill the dataset SqlDataAdapter dataAdptr = new SqlDataAdapter(); dataAdptr.SelectCommand = sqlCmd; DataSet dsStaff = new DataSet("directory"); dataAdptr.Fill(dsStaff, "staff");

// Create an XML document and read the data set into it XmlDocument xmlDom = new XmlDocument(); xmlDom.LoadXml(dsStaff.GetXml()); return xmlDom; }

get the data set as a string and then load it into an XML document

add XML system library

this is all the same as before


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clean XML returned

we could easily manipulate this XML further using DOM

programming


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• Microsoft Access database uses an OLEDB JET connection string • System.Data.OleDb

• old fashioned

• insecure

• popular

• Next example uses DOM to read data from Access in XML format


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using System.Data.OleDb

[WebMethod] public XmlDocument getDirectoryOledb() { // Open OLEDB connection to Access database OleDbConnection DBconnection = new OleDbConnection ("PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA Source=e:\\webareas\\mk05\\phoneBook.mdb"); DBconnection.Open();

// Create and execute SQL query OleDbCommand cmdSelectUsers = new OleDbCommand

("SELECT firstname, surname, phone, location FROM staff, DBconnection); OleDbDataReader dataStaff = cmdSelectUsers.ExecuteReader();

// Instantiate an XML document XmlDocument xmlDom = new XmlDocument(); xmlDom.AppendChild(xmlDom.CreateElement("", "phoneBook", "")); XmlElement xmlRoot = xmlDom.DocumentElement;

// Create local references XmlElement xmlStaff, xmlFname, xmlSname, xmlTel, xmlLoc; XmlText xmlTxt; string firstname, surname, telephone, location;


identify the root element

add the OleDb sytsem library

Web Services while ( dataStaff.Read() ) {

// Retrieve the records from the data setfirstname = dataStaff.GetString(0);surname = dataStaff.GetString(1);telephone = dataStaff.GetInt32(2).ToString();location = dataStaff.GetString(3);// Create XML elements for the records and append them to the DOMxmlStaff = xmlDom.CreateElement("staff");xmlFname = xmlDom.CreateElement("fname");xmlText = xmlDom.CreateTextNode(firstname);xmlFname.AppendChild(xmlText);xmlStaff.AppendChild(xmlFname);xmlSname = xmlDom.CreateElement("sname");xmlText = xmlDom.CreateTextNode(surname);xmlSname.AppendChild(xmlText);xmlStaff.AppendChild(xmlSname);xmlTel = xmlDom.CreateElement("phone");xmlText = xmlDom.CreateTextNode(telephone);xmlTel.AppendChild(xmlText);xmlStaff.AppendChild(xmlTel);xmlLoc = xmlDom.CreateElement("loc");xmlText = xmlDom.CreateTextNode(location);xmlLoc.AppendChild(xmlText);xmlStaff.AppendChild(xmlLoc);xmlRoot.AppendChild(xmlStaff);

} dataStaff.Close(); DBconnection.Close(); return xmlDom;}

create and append elements into the DOM

loop over the data set

return the DOM


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looks remarkably similar to the SQL Server web service


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• Create a .NET web service that accesses XML from a URL

• That URL could itself be a web service

• getDirectory.php reads a staff telephone directory from a MySQL database• returns a DOM object

• is a RESTful web service

• uses the PHP5 DOM model• stuweb.cms.gre.ac.uk

Web Services<?phpheader('Content-type: text/xml');require '/home/mkg01/include/mysql.php';$link = mysql_connect($host, $user, $passwd);mysql_select_db($dbName);$query = 'SELECT firstname, surname, phone, location FROM staff ORDER BY surname';$result = mysql_query($query,$link);if ( mysql_num_rows($result) > 0 ) { $xmlDom = new DOMDocument(); $xmlDom->appendChild($xmlDom->createElement('directory')); $xmlRoot = $xmlDom->documentElement; while ( $row = mysql_fetch_row($result) ) { $xmlPerson = $xmlDom->createElement('staff'); $xmlFname = $xmlDom->createElement('fname'); $xmlText = $xmlDom->createTextNode($row[0]); $xmlFname->appendChild($xmlText); $xmlPerson->appendChild($xmlFname); $xmlSname = $xmlDom->createElement('sname'); $xmlText = $xmlDom->createTextNode($row[1]); $xmlSname->appendChild($xmlText); $xmlPerson->appendChild($xmlSname); $xmlTel = $xmlDom->createElement('phone'); $xmlText = $xmlDom->createTextNode($row[2]); $xmlTel->appendChild($xmlText); $xmlPerson->appendChild($xmlTel); $xmlLoc = $xmlDom->createElement('loc'); $xmlText = $xmlDom->createTextNode($row[3]); $xmlLoc->appendChild($xmlText); $xmlPerson->appendChild($xmlLoc); $xmlRoot->appendChild($xmlPerson); }}echo $xmlDom->saveXML();?>

getDirectory.php

loop over the query results and create a

DOM document

just like the previous C# example

query MySQL database

output XML mime type

write the DOM back to the client


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a now familiar sight


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[WebMethod]public XmlDocument getDirectoryUrlDataSet(){ // Instantiate a data set and read XML into it from a URL DataSet dataSetUrl = new DataSet("directory"); dataSetUrl.ReadXml

("http://stuweb.cms.gre.ac.uk/~mkg01/staffWS/getDirectory.php");

// Create an XML document and read the data set into it XmlDocument xmlDom = new XmlDocument(); xmlDom.LoadXml(dataSetUrl.GetXml()); // And return it to the client return xmlDom;}

This is not the best way to read from an external resource as there is no way to validate the incoming data

Use an XmlTextReader instead


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[WebMethod]public XmlDocument getDirectoryUrlTextReader(){ // Instantiate an XML text reader and read XML into it from a URL XmlTextReader myXmlTextReader = new XmlTextReader


// Create an XML document and load the XML text reader into it XmlDocument xmlDom = new XmlDocument(); xmlDom.Load(myXmlTextReader); // And return it to the client return xmlDom;}

XmlTextReader is a stream XML processor rather like SAX although SAX is not supported by .NET. This checks that the XML is well formed and enables the XML to be

validated as it is read.


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Telephone Directory Web Service[WebMethod]public XmlDocument getDirectoryUrlValidating(){ // Instantiate an XML text reader and read XML into it from a URL XmlTextReader xmlTR = new XmlTextReader

("http://stuweb.cms.gre.ac.uk/~mkg01/staffWS/getDirectory.php"); XmlValidatingReader xmlVR = new XmlValidatingReader(xmlTR); xmlVR.ValidationType = System.Xml.ValidationType.DTD;

// Assign a validation failure event handler xmlVR.ValidationEventHandler += new ValidationEventHandler(ValidationHandler); xmlVR.Read();

// Create an XML document and load the XML text reader into it XmlDocument xmlDom = new XmlDocument(); xmlDom.Load(xmlTR);

// And return it to the client return xmlDom;}

method to handle a validation failure –

although it is less than clear what to do with a validation failure in a

web service


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XML Aggregation

• Web services are used to create interfaces to data resources

• Using DOM structures we can operate on the data

• Data from many sources can be aggregated into a single DOM object

• .NET provides alternative programmatic approaches to XML• DataSet

• XmlNavigator

• XSLT

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XML Aggregation[WebMethod]public XmlDocument getDirectories(){ // Instantiate an XML document and read the SQL database into it XmlDocument xmlDom1 = new XmlDocument(); xmlDom1 = getDirectoryDom();

// Instantiate an XML text reader and read XML into it from a URL XmlTextReader myXmlTextReader = new XmlTextReader


// Create an XML document and load the XML text reader into it XmlDocument xmlDom2 = new XmlDocument(); xmlDom2.Load(myXmlTextReader);

foreach ( XmlElement xmlNode in xmlDom2.DocumentElement.ChildNodes ) {

xmlDom1.DocumentElement.AppendChild(xmlNode);

}

// And return it to the client return xmlDom1;}

reading direct from the method we created earlier

loop over each node in the second DOM and

append the node to the root in the first DOM


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XML Aggregation

Ooops!

Clearly something is not happy here. The nodes do not belong to the document we are adding them into – we

need to import them or else roll up out sleeves and do it manually with some DOM programming


Web Services

XML Aggregation

• This does the trick

• Although we could always do it the hard way• which would allow us to adjust the DOM structure as

we migrate nodes

// Loop over each child node in second XML documentforeach ( XmlNode xmlNode2 in xmlDom2.DocumentElement.ChildNodes ){ // Import each child node into the first XML document XmlNode xmlNode1 = xmlDom1.ImportNode(xmlNode2, true); xmlDom1.DocumentElement.AppendChild(xmlNode1);}


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XML Aggregation// Create some pointersXmlElement xmlStaff, xmlEle;XmlText xmlTxt;

// Loop over the staff nodes in the second XML documentforeach ( XmlNode xmlStaffNode in xmlDom2.DocumentElement.ChildNodes ){ // Create a new staff element xmlStaff = xmlDom1.CreateElement(xmlStaffNode.Name);

// Loop over the children of the staff element in the second document foreach ( XmlNode xmlNode in xmlStaffNode.ChildNodes ) { // Create new child elements xmlEle = xmlDom1.CreateElement(xmlNode.Name); xmlTxt = xmlDom1.CreateTextNode(xmlNode.InnerText); xmlEle.AppendChild(xmlext); xmlStaff.AppendChild(xmlEle); }

// Append the new staff element to the first XML document xmlDom1.DocumentElement.AppendChild(xmlStaff);}

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hurrah!

either way we manage to aggregate the

content


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XML Aggregation

• Of course we could try a different approach using data sets instead of XML documents

• Data sets provide a useful merge method• although this will complain if data types do not match

• e.g. are telephone numbers strings?

• converting everything to strings is one work around


Web Services

[WebMethod]public XmlDocument getDirectories2(){ // Create an XML text reader to read the ASP.NET Access web service XmlTextReader xmlReader1 = new XmlTextReader

("http://cms-stu-iis.gre.ac.uk/mk05/..../getDirectoryOledb"); DataSet dataSetReader1 = new DataSet(); dataSetReader1.ReadXml(xmlReader1);

// Create an XML text reader to read the PHP web service XmlTextReader xmlReader2 = new XmlTextReader

("http://stuweb.cms.gre.ac.uk/~mkg01/staffWS/getDirectory.php"); // Create another data set and load it from the text reader DataSet dataSetReader2 = new DataSet(); dataSetReader2.ReadXml(xmlReader2);

// Merge the two data sets dataSetReader1.Merge(dataSetReader2);

// Instantiate an XML document and load the merged data set into it XmlDocument xmlDom = new XmlDocument(); xmlDom.LoadXml(dataSetReader1.GetXml()); // And return it to the client return xmlDom;}

data sets provide a merge method although it will complain

if the data types don’t match


Web Services

<?phpheader('Content-type: text/xml');require '/home/mkg01/include/mysql.php';$link = mysql_connect($host, $user, $passwd);mysql_select_db($dbName);$query = 'SELECT firstname, surname, phone, location FROM staff ORDER BY surname';$result = mysql_query($query,$link);if ( mysql_num_rows($result) > 0 ) { $xmlDom = new DOMDocument(); $xmlDom->appendChild($xmlDom->createElement('directory')); $xmlRoot = $xmlDom->documentElement; while ( $row = mysql_fetch_row($result) ) { $xmlPerson = $xmlDom->createElement('staff'); $xmlFname = $xmlDom->createElement('fname'); $xmlText = $xmlDom->createTextNode($row[0]); $xmlFname->appendChild($xmlText); $xmlPerson->appendChild($xmlFname); $xmlSname = $xmlDom->createElement('sname'); $xmlText = $xmlDom->createTextNode($row[1]); $xmlSname->appendChild($xmlText); $xmlPerson->appendChild($xmlSname); $xmlTel = $xmlDom->createElement('phone'); $xmlText = $xmlDom->createTextNode($row[2]); $xmlTel->appendChild($xmlText); $xmlPerson->appendChild($xmlTel); $xmlLoc = $xmlDom->createElement('loc'); $xmlText = $xmlDom->createTextNode($row[3]); $xmlLoc->appendChild($xmlText); $xmlPerson->appendChild($xmlLoc); $xmlRoot->appendChild($xmlPerson); }}

we've seen all this before

soapAggregator.php

do the same thing with PHP


Web Services

$client = new SoapClient("http://cms-stu-iis.gre.ac.uk.../phoneBook.asmx?WSDL");$xmlString = $client->getDirectoryDom()->getDirectoryDomResult->any;$xmlDom2 = new DOMDocument();$xmlDom2->loadXML($xmlString);

foreach ( $xmlDom2->documentElement->childNodes as $staffNode ) { $xmlPerson = $xmlDom1->createElement($staffNode->nodeName); foreach ( $staffNode->childNodes as $xmlNode ) { $xmlElement = $xmlDom1->createElement($xmlNode->nodeName); $xmlText = $xmlDom1->createTextNode($xmlNode->nodeValue); $xmlElement->appendChild($xmlText); $xmlPerson->appendChild($xmlElement); } $xmlRoot->appendChild($xmlPerson);}

echo $xmlDom1->saveXML();?>

soapAggregator.php

create a SOAP client using the ASP.NET WSDL

merge the two DOM objects


Web Services


Web Services

Adding A Processing Instruction

[WebMethod]public XmlDocument showDirectory(){ // Instantiate an XML document and read the SQL database into it XmlDocument xmlDom = new XmlDocument(); xmlDom = getDirectoryDom();

// Create a PI and append it to the document XmlProcessingInstruction PI = xmlDom.CreateProcessingInstruction

("xml-stylesheet", "href='directory.xsl' type='text/xsl'"); xmlDom.InsertBefore(PI, xmlDom.DocumentElement);

// Return the document to the client return xmlDom;}


Web Services

oh no!

because this is a Web Method the processing instructions has

been stripped out


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Adding Processing Instruction

• It is not entirely surprising that the processing instruction is filtered out from a web service

• Add a Generic Handler to the project• .ashx

• Add code to aggregate XML and add a processing instruction into the page load event

• Return all of the XML using the Response object

• Don’t forget to also use the Response object to send out the correct mime type• text/xml


Web Services

using System.IO;

private void Page_Load(object sender, EventArgs e){ // Instantiate an XML text reader and read XML into it from a URL XmlTextReader xmlTextReader1 = new XmlTextReader

("http://cms-stu-iis.gre.ac.uk/mk05/.../getDirectoryDom");

// Create an XML document and load the XML text reader into it XmlDocument xmlDom1 = new XmlDocument(); xmlDom1.Load(xmlTextReader1);

// Instantiate an XML text reader and read XML into it from a URL XmlTextReader xmlTextReader2 = new XmlTextReader


// Create an XML document and load the XML text reader into it XmlDocument xmlDom2 = new XmlDocument(); xmlDom2.Load(xmlTextReader2);


at this stage we have two XML documents obtained from two

web services


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// Loop over each child node in second XML document foreach ( XmlNode xmlNode2 in xmlDom2.DocumentElement.ChildNodes ) { // Import each child node into the first XML document XmlNode xmlNode1 = xmlDom1.ImportNode(xmlNode2, true); xmlDom1.DocumentElement.AppendChild(xmlNode1); }

// Create and insert processing instruction XmlProcessingInstruction PI = xmlDom1.CreateProcessingInstruction

("xml-stylesheet", "href=\"directory.xsl\" type=\"text/xsl\""); xmlDom1.InsertBefore(PI, xmlDom1.DocumentElement);

// Write it all back to the client StringWriter sw = new StringWriter(); XmlTextWriter xtw = new XmlTextWriter(sw); xmlDom1.WriteTo(xtw); context.Response.ContentType = "text/xml"; context.Response.Write(sw);}


output mime type

output XML


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oh hurrah!

here the XML returning to the client contains the PI linking to a simple XSLT

stylesheet


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• Try the same trick in PHP…• Add one extra line to getDirectory.php

• The nice thing about DOM is the way the code works pretty much the same in both PHP and C#

• Add the same DOM code into PHP and aggregate some XML

$xmlDom->appendChild($xmlDom->createProcessingInstruction

('xml-stylesheet', 'href="directory.xsl" type="text/xsl"'));


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XML merged and XSLT processed using PHP with

the same DOM code as used in C#


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Server Side XSLT Processing• Not all browsers support XSLT processing

• Perhaps the XSLT processing is better handled at the server• add another Generic Handler

// Create a StringWriter to write back the HTMLStringWriter sw = new StringWriter();

// Create an XSLT transformer and load in the XSLT fileXmlTextReader xsltSource = new XmlTextReader("directory.xsl");XslCompiledTransform xslt = new XslCompiledTransform();xslt.Load(xsltSource);

// Transform the XML (with a null XmlResolver)xslt.Transform(xmlDom1, null, sw);

// Return the results to the clientcontext.Response.ContentType = "text/html";context.Response.Write("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");context.Response.Write(sw);


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Server Side XSLT Processing

just when you thought that you had control over

ASP.NET a pesky meta tag appears


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SQL Insert Web Service

• So far we have been retrieving information from various databases – often we want to insert or modify.

• Visual Studio makes it easy to create a suitable web service


Web Services

[WebMethod]public string insertRecord(string txtFname, string txtSname, string txtTel, string txtLoc){ if ( txtFname == "" || txtSname == "" || txtTel == "" || txtLoc == "" ) { return "Incomplete data"; } else { int number = int.Parse(txtTel);

// Open a connection the the SQL Server SqlConnection sqlConn = new SqlConnection(); sqlConn.ConnectionString = "<SQL Server connection string>"; sqlConn.Open();

// Create a SQL query SqlCommand insertCmd = sqlConn.CreateCommand(); insertCmd.CommandType = CommandType.Text; insertCmd.CommandText = "INSERT INTO phoneBook (fname, sname, phone, loc) VALUES ('" + txtFname+ "', '" + txtSname+ "', " + number + ", '" + txtLoc + "')";

insertCmd.ExecuteNonQuery(); return "Record inserted"; }}


report validation fail

report success

validate input


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Conclusions

• It's all so easy• especially when it's RESTful

• Visual Studio does most of the work• wish we had VS for PHP

• PHPeclipse, Netbeans

• These examples show main points• coding would benefit from try catch constructs


Web Services

Questions?

Documents

More Visual Studio Data Binding and Web Services