Beginning Ajax with ASP.NET- P20

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Beginning Ajax with ASP.NET- P20

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  1. Atlas Client Script } function ComplexScriptCompleteCallback(result) { alert(“Value: “ + result); } The code for the complex data type is: public class cComplexCustomerType { public cComplexCustomerType() { } private string _Name; private string _Address; public string Name { get { return _Name; } set { _Name = value;} } public string Address { get { return _Address; } set { _Address = value; } } } The code for the web service is: [WebMethod] public cComplexCustomerType AcceptComplexDataType(cComplexCustomerType objComplexCustomerType) 261
  2. Chapter 10 { return (objComplexCustomerType); } In this example code, the web service accepts the custom business object and then returns the value. There is nothing that would stop the web service from using the properties of the business object that is passed or the web service from returning a string as opposed to the custom business object. Interrogation of the custom object returns interesting information. The following code will generate the results in Figure 10-5. This figure shows that the Name and Address properties are available along with an added member — the __serverType property. This property defines the type on the server. function ComplexScriptCompleteCallback(result) { var str = “”; debug.dump(result); for(prop in result) str += “Member: “ + prop + “\r\n”; alert(str); } Figure 10-5 A call to debug.dump() on the returned result object produces the output in Figure 10-6. The debug .dump() method displays the contents of an object in Atlas. This method will be discussed more later in this chapter. 262 Figure 10-6
  3. Atlas Client Script Caching Web Ser vices The data returned from a web service may be cached. This can be helpful in situations where data may not be time critical (for example, a web service that returns the weather forecast for a given location). This is performed in .NET by setting a value on the CacheDuration of the WebMethod() attribute. As you may have previously done when working with web services, Atlas makes it possible to call a cached web service and get the results of a web service call. Depending on the data and the time that is required to perform the calculation, the time saved by caching may be significant when factored over thousands of possible users. Take a look at some code and the result. In this example, you are just going to display the time of each call. On the first call, both times that are returned will be the same. Subsequent calls will result in the current time being updated and the cached time being the same, while the cached time is not updated until the cache duration is over. This is the code for an .aspx page: Untitled Page function GetServerTime() { CachingWebService.GetServerCachedTime(DisplayServerCachedTime); CachingWebService.GetServerCurrentTime(DisplayServerCurrentTime); } function DisplayServerCurrentTime(result) { var ctrl = document.getElementById(“NewTime”); ctrl.innerText = result; } function DisplayServerCachedTime(result) { var ctrl = document.getElementById(“StartTime”); ctrl.innerText = result; } Start Call: 263
  4. Chapter 10 New Time: In the preceding code, on a button click, two remote calls are made out to the server — a call to the GetServerCachedTime method and one to the GetServerCurrentTime method. The GetServer CachedTime method on the server returns the current server time when it is called the first time. The result of this call is cached in server memory. Subsequent calls are returned the cached result for the next 100 seconds, at which point the next request will generate a new time and a new entry in the server cache. As a result, calls to GetServercurrentTime() will result in the current time of the server being returned while calls to GetServerCachedTime() will result in a value that is up to 100 seconds old. The following is the code for a web service: [WebMethod(CacheDuration = 100)] public DateTime GetServerCachedTime() { return(DateTime.Now.ToUniversalTime()); } [WebMethod] public DateTime GetServerCurrentTime() { return (DateTime.Now.ToUniversalTime()); } Atlas uses UTC encoding for dates and time. This may create confusion for you if you don’t remember it. Personally, my system is set with the time of GMT – 5. As a result, the times that were coming back were 5 hours off. Figure 10-7 shows the results of multiple calls to the cached and noncached web services. In Figure 10-7, you will notice the two different time values. This shows that calling the cached web ser- vice returns the cached value and the noncached version returns the current value of the DateTime.Now object. 264
  5. Atlas Client Script Figure 10-7 Exposing Web Ser vices from a Web Form All of the examples you’ve explored to this point in this chapter have used a dedicated web service. It is also possible to have a web service that is exposed within an internal page of a web application. On the surface, it appears that there is no real advantage to this. However, there are two advantages to using web services that are exposed by a web form. These are: ❑ The page and web service are deployed together. There are fewer files to deploy and fewer things that can go wrong. ❑ While not having been announced as this is being written, it appears that Microsoft will be adding some special functionality that will be available only to a web service that is called within a web form. Given the early status of Atlas, more information will come out about this in the future. This next example calls back to a web service on the same .aspx page. The code for the web page is: Internal Web Service Page 265
  6. Chapter 10 function CallInternalWebService() { PageMethods.CallInternalWebService(InternalCallBack); } function InternalCallBack(result) { alert(result); } In the preceding code, note that the calling convention is not Class.MethodName(), but PageMethods .MethodName(). PageMethods is a special class that is used to call the methods internal to a page. The code-behind file is shown below. Note the addition of the System.Web.Services namespace, which is not typically specified in a code-beside or aspx page. The method displayed in the following merely returns a string as an example; however, any number of datatypes can be returned, just like a regular web service and the other examples. using System.Web.Services; ........ [WebMethod] public string CallInternalWebService() { return (“Internal Web Service Called.”); } The result of this is shown in Figure 10-8. Figure 10-8 266
  7. Atlas Client Script Atlas Extensions to JavaScript Atlas allows for the creation of rich client-side applications that run within the browser. To facilitate the creation of these applications, Atlas has created a set of extensions to the type system in JavaScript. These extensions provide many of the features of the .NET type system to the client-side web browser environment. These extensions include namespaces, inheritance, interfaces, enums, support for strings, and arrays. Language Enhancements JavaScript has been around as a language since the early betas of the Netscape Navigator 2.0 web browser appeared in late 1995 to early 1996. Since then, there have been numerous enhancements to the JavaScript language. The latest version of the language is version 1.6. With the shipment of the .NET Framework, Microsoft has released a framework that contains a set of base classes that have features across various languages, including Visual Basic, C#, and JavaScript when running native and server- side applications. Into this, steps Atlas. Atlas provides a set of enhancements on top of JavaScript as it runs in the web browser. The next sections look at these enhancements and extensions. Controls Atlas provides a set of controls, classes, and objects that may be used programmatically in JavaScript. Object The Object class is a client version of the .NET System.Object class. The only method that it imple- ments is the getType(obj) method. This method will return the type of the specified object. Array The Array class is similar in concept to the .NET System.Collections.ArrayList() class. It has several interesting members such as length, push(), and pop(). A small example is var ary = new Array(); ary.push(47); alert(“length: “ + ary.length); In this short example, the user is presented with an alert box with a length of 1. Date The Date class is conceptually similar to a client web browser version of the .NET System.DateTime class. The Date object supports a set of methods similar to the Date() class in .NET. There are methods to create a date, get various parts of a date, and set the parts of a date. For a quick example, it is possible to create a date: var dt = new Date(); dt.setFullYear(2006, 03, 26); dt.setHours(10, 12, 13, 5); alert(“Date: “ + dt.toString()); In the preceding example code, the date that is created is March 26, 2006, 10 hours, 12 minutes, 13 sec- onds, and 5 milliseconds. The resulting date is then displayed to the user in an alert() window. 267
  8. Chapter 10 Number The Number class contains several methods. There are several methods to parse the content of the num- ber as well as convert it to a string, get the exponential value, and perform other operations. Boolean The Boolean class is used for parsing traditional boolean values. It implements several methods for creating a boolean. If the passed value is a string and would return as boolean, the boolean value is returned. String The String class is a client web browser version of the .NET String class. The String() class imple- ments some of the methods that are similar to the String() class in .NET. Some of the more interesting members of the Atlas String() class are: ❑ indexOf() — The indexOf(string, startingindex) returns the value of the starting loca- tion of the specified string when at the startingindex location. ❑ lastIndexOf() — The lastIndexOf(string, startingindex) returns the value of the starting location of the last time the specified string is found. ❑ substring() — The substring(start, end) returns the substring from the starting location to the ending location. ❑ substr() — The substr(start, length) returns the substring from the starting location of the specified length. ❑ toLowerCase() — The lowercase version of the string is returned. ❑ toUpperCase() — The uppercase version of the string is returned. RegExp The RegExp class is a client web browser version of the .NET Regular Expression library. The Atlas RegExp class supports the .parse(value) method. Built-In Namespaces Atlas comes with a number of built-in namespaces and classes for managing data, HTTP communica- tion, user interface design, and other things. These are in the Sys.* namespaces. The next sections look at several of the namespaces and their associated classes. Sys.Net.WebRequest The Sys.Net namespace provides a set of classes to facilitate HTTP communications between the client and the web server. Though other classes exist within the name, the one we are going to look at is the WebRequest class. The Sys.Net.WebRequest class provides support for making HTTP requests. The following sample code, for example, makes a web request. var request; 268
  9. Atlas Client Script function MakeCall() { request = new Sys.Net.WebRequest(); var url = Sys.Net.WebRequest.createUrl(“PageThatIsCalled.aspx”, null); request.set_url(url); request.completed.add(RequestCompleted); request.timeout.add(RequestTimeOut); request.invoke(); } function RequestCompleted(objSender, evArgs) { if (blRun == true ) { var obj = objSender.get_webRequest(); var objWR = objSender.get_data(); debug.dump(objWR, “Web Content:”, true); } } Figure 10-9 shows the output of the preceding code. In this example, the content from the called page is contained within the debug.dump statement as expected. In the preceding example, a call is made out to a web page in the same directory, and its contents are displayed. Figure 10-9 Sys.Data.DataColumn The Sys.Data namespace provides a set of classes that are essentially client-side versions of the similar classes in the System.Data namespace of the .NET Framework. This namespace provides support for classes called DataColumn, DataRow, DataTable, DataView, DataFilter, DataSource, and PropertyFilter. 269
  10. Chapter 10 The Sys.Data.DataColumn class allows for the interrogation of column information within a Sys.Data.DataTable class. The DataColumn exposes the following members. These members will be useful for processing datasets and data tables that are returned from a web service. Members Description get_columnName() This method will retrieve the column name of a specific column. get_dataType() This method will retrieve the datatype of the column. get_defaultValue() This method will retrieve the default value of a column. dispose() This method will dispose() of the object and perform any nec- essary cleanup. The following example code will interrogate a returned dataset. The first thing that is necessary is to get a datatable. This is performed by calling the result.getItem(0) method. function MethodReturn(result) { var i = 0; var str = “”; var strColInfo = “”; var strReturn = “”; for (prop in result) str += “Property: “ + prop + “\r\n”; alert(str); var tbl1 = result.getItem(0); for(i = 0; i < tbl1.get_columns().length; i++) { strColInfo += tbl1.get_columns()[i].get_columnName() + “:” + tbl1.get_columns()[i].get_dataType() + strReturn; } document.getElementById(“ColInfo”).innerHTML = strColInfo } In the preceding code, a web service returns a dataset in the result variable to the MethodReturn() JavaScript function. There is a for() loop that returns the properties/members of the result object. This is then presented to the user in an alert() box. This alert() box is only for information’s sake. The first table in the dataset is pulled out of the dataset by calling result.getItem(0). Within the first table, the next for() loop iterates through the columns returned, gets the datatype, and creates a string, and after the for() loop exits, the data is presented to the user. Figure 10-10 shows the output of the preceding code. One thing to notice is that the get_dataType() returns information. 270
  11. Atlas Client Script Figure 10-10 Sys.Data.DataTable The Sys.Data.DataTable class provides all information for integration with the System.Data .DataTable. The DataTable exposes the following members that may be of interest. Members Description get_columns() This method will return an array of DataColumns within the DataTable. get_keys() This method will return an array of DataColumns that contain various keys within the DataTable. get_isDirty() This method will return a boolean indicating whether or not updates have been made on the DataTable object. get_length() This method will return the number of rows within the DataTable. add() The add method will allow the addition of a DataRow. clear() The clear() method will clear the contents of the DataTable. getChanges() The getChanges() method will provide a set of DataRows that have changed. getColumn() The getColumn() method will provide the specified column. getItem() The getItem() method will provide the specified row. This method is very important. remove() The remove() will remove the specified row. dispose() Performs the standard dispose mechanism. 271
  12. Chapter 10 The following is some code that will iterate through the rows of a DataTable: function MethodReturn(result) { var i = 0; var str = “”; var strRowsInfo = “”; var strReturn = “”; //get a datatable var tbl1 = result.getItem(0); for(i = 0; i < tbl1.get_length(); i++) { //tbl1.getItem(i) will return the ith DataRow //getProperty(“Column Name”) will return the column value from a DataRow strRowsInfo += tbl1.getItem(i).getProperty(“ProjectName”) + strReturn; } document.getElementById(“RowInfo”).innerHTML = strRowsInfo; } In the preceding code, a dataset is returned. The first datatable is obtained by the call to getItem(0). Then the DataRows are iterated. This is done by the for() loop. To get at the value of a column in a specific row, we use the getProperty(“ProjectName”) method. This method returns the value from the column ProjectName in the example. Some example output from the preceding code is shown in Figure 10-11. Figure 10-11 Sys.Data.DataRow The Sys.Data.DataRow class is the Atlas version of the System.Data.DataRow class. The DataRow has a set of properties and is designed for accessing a single row of data from a data table. For example, the DataRow.getProperty(“ColumnName”) method shown in the previous code will return the value of that specific column in that DataRow. 272
  13. Atlas Client Script For more information about this namespace and classes and others, you can check out http://atlas .asp.net/ and http://atlas.asp.net/docs for updated documentation from Microsoft along with the site for this book http://BeginningAjax.com. Registering Namespaces and Classes in Atlas JavaScript is a fairly simple scripting language. When implemented in a web browser environment, it lacks many features that are common to modern programming languages. As a result, it is necessary for Atlas to add functionality to create namespaces, classes, and other items that are familiar to developers who use modern programming languages. There are several different mechanisms to register classes in Atlas. Type.registerNameSpace A namespace is used to group common functionality together. The Type.registerNameSpace() method is used to register a namespace in Atlas-enabled JavaScript. The proper call for this method is as follows. Type.registerNameSpace(‘NamespaceName’); In this example, NamespaceName is a string representing the name of the namespace. NamespaceName.ClassName.registerClass A class is a set of methods and data that provide a specific piece of functionality. Atlas provides a mecha- nism to register classes. This is performed within the following call. NamespaceName.ClassName.registerClass(‘NamespaceName.ClassName’, ParentClass, InterfaceImplemented); In this example, the NamespaceName.ClassName is a string representing the name of the class. If the class that is being registered is to inherit from another class, that parent class is passed as the second parameter. The final parameter is any interface that may be implemented within the class. Take note that not all of the parameters are required. NamespaceName.ClassName.registerAbstractClass An abstract class is one that contains methods that are not actually implemented within the class. Also, abstract classes cannot be instantiated — their only purpose is to be used as a model for child classes. The definition is performed by the following code. NamespaceName.ClassName.registerAbstractClass(‘NamespaceName.ClassName’, ParentClass, InterfaceImplemented); In this example, the NamespaceName.ClassName is a string representing the name of the class. If the class that is being registered is to inherit from another class, that parent class is passed as the second parameter. The final parameter is any interface that may be implemented within the class. Take note that not all of the parameters are required. 273
  14. Chapter 10 NamespaceName.ClassName.registerSealedClass A sealed class is one that may not be inherited from. The definition is performed by the following code. NamespaceName.ClassName.registerSealedClass(‘NamespaceName.ClassName’, ParentClass, InterfaceImplemented); In this example, the NamespaceName.ClassName is a string representing the name of the class. If the class that is being registered is to inherit from another class, that parent class is passed as the second parameter. The final parameter is any interface that may be implemented within the class. Take note that not all of the parameters are required. InterfaceName.registerInterface An interface essentially states that a class implements a specific set of methods. The interface is defined by registering an interface. This is performed by the following code. InterfaceName.registerInterface(‘InterfaceName’); In this example, the InterfaceName is merely a string representing the name of the interface that is to be implemented. Note that by convention all interfaces are named with a capital “I” prefix. NamespaceName.ClassName.registerBaseMethod If a class is going to be specifically overridden in a base class, the method must be marked in the base class. This is performed by the following code: NamespaceName.ClassName.registerBaseMethod(class, “methodname”); For example, the class will most likely be defined as the current class in JavaScript (this). A good candi- date for the method name is the dispose method. Namespaces and Classes Namespaces allow for the grouping of classes, methods, objects, and data that are closely related. Atlas includes functionality on the Type object to add namespaces and classes. These are accomplished through the Type.registerNamespace and Class.registerClass methods. Try It Out Adding a Namespace and Class through Atlas The steps necessary to add a namespace and class to JavaScript through Atlas are: 1. The atlas:ScriptManager must be added to an .aspx page. The script manager will add the appropriate script references. 2. Register a namespace. This is performed through the Type.registerNamespace method. In this example, the string NamespaceName is just an example name for a namespace: Type.registerNamespace(“NamespaceName”); 274
  15. Atlas Client Script 3. Define the contents of a class: ExampleNamespace.cComplexCustomerType = function(Name, Address) { var _Name = Name; var _Address = Address; this.getName = function() { return _Name; } this.setName = function(val){ _Name = val; } this.getAddress = function() { return _Address; } this.setAddress = function(val){ _Address = val; } this.Dispose = function(){ alert(“disposing component with Customer Name:” + this.getName() + “ @ “ + this.getAddress()); } } 4. Register the class: Type.registerClass(“ExampleNamespace.cComplexCustomerType”, Web.IDisposible); 5. To add standard methods, such as toString(), to a class, use the prototype member: ExampleNamespace.cComplexCustomerType.prototype.toString = function(){ return this.getName() + “ at “ + this.getAddress(); } Adding an item through the prototype member results in sharing of the member between instances. Sharing of objects defined with the prototype member must be avoided or unusual results may occur. Conceptually, this is similar to static/shared members in .NET. Now that a class has been created a program can use the class. The following code will use the class and display the .toString() value of the customer object: var objCust = new ExampleNamespace.cComplexCustomerType(“Acme”, “Wileyville, USA”); alert(objCust.toString()); Figure 10-12 shows the result. Figure 10-12 275
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