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DOT NET FOR BEGINNERS PDF

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An example of the second category is a class witha System. FileStream member For the first category, it makes sense to implement IDisposable and overrideFinalize. This allows the object user to do the right thing by calling Dispose, but alsoprovides a fallback of freeing the unmanaged resource in the Finalizer, should the callingcode fail in its duty.

However this logic does not apply to the second category of class,with only managed resources. In this case implementing Finalize is pointless, as managedmember objects cannot be accessed in the Finalizer. This is because there is no guaranteeabout the ordering of Finalizer execution. So only the Dispose method should beimplemented. If you think about it, it doesnt really make sense to call Dispose onmember objects from a Finalizer anyway, as the member objects Finalizer will do therequired cleanup.

For classes that need to implement IDisposable and override Finalize, seeMicrosofts documented pattern. Note that some developers argue that implementing a Finalizer is always a bad idea,as it hides a bug in your code i. A less radical approach is toimplement Finalize but include a Debug.

Assert at the start, thus signalling the problem indeveloper builds but allowing the cleanup to occur in release builds. Do I have any control over the garbage collection algorithm? A little. For example the System. GC class exposes a Collect method, which forces thegarbage collector to collect all unreferenced objects immediately Also there is a gcConcurrent setting that can be specified via the applicationconfiguration file.

This specifies whether or not the garbage collector performs some of itscollection activities on a separate thread. The setting only applies on multi-processormachines, and defaults to true. How can I find out what the garbage collector is doing? Lots of interesting statistics are exported from the. NET runtime via the. Use Performance Monitor to view them What is the lapsed listener problem? The lapsed listener problem is one of the primary causes of leaks in.

It occurs when a subscriber or listener signs up for a publishers event, butfails to unsubscribe. The failure to unsubscribe means that the publisher maintains areference to the subscriber as long as the publisher is alive. For some publishers, this maybe the duration of the application This situation causes two problems.

The obvious problem is the leakage of thesubscriber object. The other problem is the performance degredation due to the publishersending redundant notifications to zombie subscribers.

There are at least a couple of solutions to the problem. The simplest is to make surethe subscriber is unsubscribed from the publisher, typically by adding an Unsubscribe method to the subscriber. Another solution, documented here by Shawn Van Ness, is tochange the publisher to use weak references in its subscriber list.

What is serialization? Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process, i. Does the. NET Framework have in-built support for serialization? There are two separate mechanisms provided by the. Both are available for use inyour own code I want to serialize instances of my class. It depends. However, on the plus side, XmlSerializer has good support forcustomising the XML document that is produced or consumed.

XmlSerializers featuresmean that it is most suitable for cross-platform work, or for constructing objects fromexisting XML documents SoapFormatter and BinaryFormatter have fewer limitations than XmlSerializer.

Theycan serialize private fields, for example. However they both require that the target classbe marked with the [Serializable] attribute, so like XmlSerializer the class needs to bewritten with serialization in mind. Also there are some quirks to watch out for - forexample on deserialization the constructor of the new object is not invoked.

The choice between SoapFormatter and BinaryFormatter depends on the application. BinaryFormatter makes sense where both serialization and deserialization will beperformed on the. NET platform and where performance is important.

SoapFormattergenerally makes more sense in all other cases, for ease of debugging if nothing else. Can I customise the serialization process? XmlSerializer supports a range of attributes that can be used to configureserialization for a particular class.

For example, a field or property can be marked with the[XmlIgnore] attribute to exclude it from serialization. Another example is the[XmlElement] attribute, which can be used to specify the XML element name to be usedfor a particular property or field.

Ultimate control of the serialization process can beacheived by implementing the the ISerializable interface on the class whose instances areto be serialized. Why is XmlSerializer so slow? There is a once-per-process-per-type overhead with XmlSerializer. So the first timeyou serialize or deserialize an object of a given type in an application, there is a significantdelay.

This normally doesnt matter, but it may mean, for example, that XmlSerializer is apoor choice for loading configuration settings during startup of a GUI application Why do I get errors when I try to serialize a Hashtable?

XmlSerializer will refuse to serialize instances of any class that implementsIDictionary, e. SoapFormatter and BinaryFormatter do not have thisrestriction.

XmlSerializer is throwing a generic "There was an error reflectingMyClass" error. How do I find out what the problem is? Look at the InnerException property of the exception that is thrown to get a morespecific error message What are attributes? There are at least two types of. NET attribute. The first type I will refer to asa metadata attribute - it allows some data to be attached to a class or method. This databecomes part of the metadata for the class, and like other class metadata can beaccessed via reflection.

An example of a metadata attribute is [serializable], which can beattached to a class and means that instances of the class can be serialized. Context attributes use a similar syntaxto metadata attributes but they are fundamentally different. If you have encountered Keith Browns universal delegator youll befamiliar with this idea. CAS is the part of the. NET security model that determines whether or not code isallowed to run, and what resources it can use when it is running.

For example, it is CASthat will prevent a. NET web applet from formatting your hard disk. How does CAS work? The CAS security policy revolves around two key concepts - code groups andpermissions. NET assembly is a member of a particular code group, and each codegroup is granted the permissions specified in a named permission set.

For example, using the default security policy, a control downloaded from a web sitebelongs to the Zone - Internet code group, which adheres to the permissions defined bythe Internet named permission set. Naturally the Internet named permission setrepresents a very restrictive range of permissions.

Im having some trouble with CAS. How can I troubleshoot the problem? Caspol has a couple of options that might help. First, you can ask caspol to tell youwhat code group an assembly belongs to, using caspol -rsg.

Similarly, you can ask whatpermissions are being applied to a particular assembly using caspol -rsp 9. I cant be bothered with CAS. Can I turn it off? Yes, as long as you are an administrator.

Just run: Can I look at the IL for an assembly? MS supply a tool called Ildasm that can be used to view the metadata and IL foran assembly. Can source code be reverse-engineered from IL? Yes, it is often relatively straightforward to regenerate high-level source from IL. How can I stop my code being reverse-engineered from IL? You can buy an IL obfuscation tool. These tools work by optimising the IL in such away that reverse-engineering becomes much more difficult Of course if you are writing web services then reverse-engineering is not a problemas clients do not have access to your IL.

Can I write IL programs directly? WriteLine class System. An exe assembly willbe generated. A couple of simple examples are that you can throw exceptions that are notderived from System. Exception, and you can have non-zero-based arrays. This subject causes a lot of controversy, as youll see if you read the mailing listarchives. Take a look at the following two threads: Thisis mostly good, as a lot of COM was ugly.

Generally speaking,. NET allows you topackage and use components in a similar way to COM, but makes the whole thing abit easier. Is DCOM dead? Pretty much, for. NET developers. Of course DCOM will still Not immediately. The approach for. NET ones. Various tools and attributes were provided to make this aspainless as possible. Start with this message: Can I use COM components from. NET programs? COM components are accessed from the. NET-compatible interfaces. For oleautomation interfaces, the RCWcan be generated automatically from a type library.

For non-oleautomation interfaces,it may be necessary to develop a custom RCW which manually maps the typesexposed by the COM interface to. NET-compatible types. Can I use. This is similar to a RCW see previous question , but works in the oppositedirection. Again, if the wrapper cannot be automatically generated by the. Also, for COM to see the. NET component, the. NET component mustbe registered in the registry.

Is ATL redundant in the. NET world? ATL will continue to be valuable for writing COM components for some time,but it has no place in the. NET world. How do I spawn a thread? Create an instance of a System. Thread object, passing it an instanceof a ThreadStart delegate that will be executed on the new thread.

For example: ThreadMain method: WaitUntilFinished ; How do I stop a thread? There are several options. First, you can use your own communicationmechanism to tell the ThreadStart method to finish. Alternatively the Thread class hasin-built support for instructing the thread to stop.

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The two principle methods areThread. Interrupt and Thread. The former will cause aThreadInterruptedException to be thrown on the thread when it next goes into aWaitJoinSleep state.

In other words, Thread. Interrupt is a polite way of asking thethread to stop when it is no longer doing any useful work. In contrast, Thread. Abort throws a ThreadAbortException regardless of what the thread is doing. Furthermore,the ThreadAbortException cannot normally be caught though the ThreadStarts finallymethod will be executed.

Abort is a heavy-handed mechanism which shouldnot normally be required. How do I use the thread pool? By passing an instance of a WaitCallback delegate to theThreadPool.

How do I know when my thread pool work item has completed? There is no way to query the thread pool for this information. You must put codeinto the WaitCallback method to signal that it has completed. Events are useful forthis. Maybe, but be careful. ReaderWriterLock is used to allow multiple threads toread from a data source, while still granting exclusive access to a single writer thread.

This makes sense for data access that is mostly read-only, but there are somecaveats.

First, ReaderWriterLock is relatively poor performing compared toMonitor. Second, you need to be verysure that the data structures you are accessing fully support multithreaded readaccess.

Finally, there is apparently a bug in the v1. Ian Griffiths has some interesting discussion on ReaderWriterLock here and here.

Yes, in the System. Diagnostics namespace. There are two main classes that dealwith tracing - Debug and Trace. They both work in a similar way - the difference isthat tracing from the Debug class only works in builds that have the DEBUG symboldefined, whereas tracing from the Trace class only works in builds that have theTRACE symbol defined. Typically this means that you should useSystem.

WriteLine for tracing that you want to work in debug andrelease builds, and System. WriteLine for tracing that you want towork only in debug builds. Can I redirect tracing to a file? The Debug and Trace classes both have a Listeners property, which is acollection of sinks that receive the tracing that you send via Debug. WriteLine andTrace. WriteLine respectively. By default the Listeners collection contains a single sink,which is an instance of the DefaultTraceListener class.

Log method. This is useful when debugging, but if youre trying to trace a problem at acustomer site, redirecting the output to a file is more appropriate. Fortunately, theTextWriterTraceListener class is provided for this purpose. Create, FileAccess. Write ; Trace. WriteLine "This will be writen to c: Flush ;Note the use of Trace.

Clear to remove the default listener. If you dont dothis, the output will go to the file and OutputDebugString. Typically this is not whatyou want, because OutputDebugString imposes a big performance hit. Can I customise the trace output?

You can write your own TraceListener-derived class, and direct all outputthrough it. Heres a simple example, which derives from TextWriterTraceListener andtherefore has in-built support for writing to files, as shown above and adds timinginformation and the thread ID for each trace line: Write method isnot overridden for example. The beauty of this approach is that when an instance of MyListener is added to theTrace. Listeners collection, all calls to Trace.

WriteLine go through MyListener,including calls made by referenced assemblies that know nothing about theMyListener class. Are there any third party logging components available? Log4net is a port of the established log4j Java logging component. How does. NET remoting work? NET remoting involves sending messages along channels.

Support is provided for multiple message serializarion formats. But either channel can use either serializationformat. There are a number of styles of remote access: Each incoming request from a client is serviced by a new object. Theobject is thrown away when the request has finished.

All incoming requests from clients are processed by a single serverobject. This is the old stateful D COM model whereby the clientreceives a reference to the remote object and holds that reference thus keeping theremote object alive until it is finished with it.

Distributed garbage collection of objects is managed by a system called leased basedlifetime. Each object has a lease time, and when that time expires the object isdisconnected from the. NET runtime remoting infrastructure. Objects have a defaultrenew time - the lease is renewed when a successful call is made from the client tothe object. The client can also explicitly renew the lease. NET program? Here is an example of C calling theWin32 MessageBox function: How do I write to the application configuration file at runtime?

You dont. See http: What is the difference between an event and a delegate? An event is just a wrapper for a multicast delegate. Adding a public event to aclass is almost the same as adding a public multicast delegate field.

In both cases,subscriber objects can register for notifications, and in both cases the publisher objectcan send notifications to the subscribers. However, a public multicast delegate has theundesirable property that external objects can invoke the delegate, something wednormally want to restrict to the publisher. Hence events - an event adds publicmethods to the containing class to add and remove receivers, but does not make theinvocation mechanism public.

See this post by Julien Couvreur for more discussion. What size is a. NET object? Each instance of a reference type has two fields maintained by the runtime - amethod table pointer and a sync block. These are 4 bytes each on a bit system,making a total of 8 bytes per object overhead. Obviously the instance data for thetype must be added to this to get the overall size of the object. So, for example,instances of the following class are 12 bytes each: Values types have no equivalent overhead.

Will my. NET app run on bit Windows? The OSdecides which to use based on the PE header of the executable. Normally you specify any cpu, andyour app will run as bit on bit Windows and bit on bit Windows. Howeverif you have some bit native code in your app loaded via COM interop, forexample , you will need to specify x86, which will force bit Windows to load yourapp in a bit process. Some more explanation here: What is reflection?

NET compilers produce metadata about the types defined in the modulesthey produce. This metadata is packaged along with the module modules in turn arepackaged together in assemblies , and can be accessed by a mechanism calledreflection. The System. Using reflection to access. Reflection can also be used to dynamically invoke methods seeSystem. InvokeMember , or even create types dynamically at run-time seeSystem. Generics, anonymous methods, partial classes, iterators, property visibility separate visibility for get and set and static classes.

What are the new 2. Generics are useful for writing efficient type-independent code, particularlywhere the types might include value types. The obvious application is containerclasses, and the. Generic namespace. Heres a simple example of a genericcontainer class being used: Add 10 ;Anonymous methods reduce the amount of code you have to write when usingdelegates, and are therefore especially useful for GUI programming.

Heres anexample AppDomain. WriteLine "Processending Heres some sample code: WriteLine r ; Console. It effectively synthethises animplementation of IEnumerator, something we had to do manually in. Whats the problem with.

NET generics? NET generics work great for container classes. But what about other uses? Well,it turns out that. NET generics have a major limitation - they require the typeparameter to be constrained. For example, you cannot do this: Dispose isnot a method on System.

Object, so the compilation fails. We can useconstraints to say that T implements a particular interface, but we cant dilute that tosimply say that T implements a particular method.

In fact, after writing generic code with interface constraints, we quickly see that wehavent gained much over non-generic interface-based programming. For example,we can easily rewrite the Disposer class without generics: Bruce Eckel: Whats new in the.

Here is a selection of new features in the. Note that C has special syntax for this type, e. Threading namespace. Cryptography namespace. Ipcnamespace, for optimised intra-machine communication. Click here to Register in Naukri.

Net 1. Describe the role of inetinfo. NET requests among other things. When an ASP. NET request is received usually a file with. Write andResponse. Write allows you to write formatted output. What methods are fired during the page load? Init - when the page is instantiated Load - when the page is loaded into server memory PreRender - the brief moment before the page is displayed to the user as HTML Unload - when page finishes loading.

When during the page processing cycle is ViewState What namespace does the Web page belong in the. NETFramework class hierarchy? CodeBehind is relevant to Visual Studio. NET only. When you have a complex control, like DataGrid, writing anevent processing routine for each object cell, button, row, etc. The controls can bubble up their eventhandlers,allowing the main DataGrid event handler to take care of itsconstituents.

Suppose you want a certain ASP. NET function executed onMouseOver for a certain button. Where do you add an eventhandler? Add an OnMouseOver attribute to the button. Add "onmouseover","someClientCodeHere ;" ; What data types do the RangeValidator control support? Integer, String, and Date. Explain the differences between Server-side and Client-side code? Server-side code executes on the server. Client-side codeexecutes in the clients browser.

What type of code server or client is found in a Code-Behind class?

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The answer is server-side code since code-behind is executedon the server. However, during the code-behinds execution on theserver, it can render client-side code such as JavaScript to beprocessed in the clients browser. But just to be clear, code-behindexecutes on the server, thus making it server-side code. Should user input data validation occur server-side orclient-side?

All user input data validation should occur on the server at aminimum. Additionally, client-side validation can be performedwhere deemed appropriate and feasable to provide a richer, moreresponsive experience for the user. What is the difference between Server. Transfer and Why would I choose one over the other? Transfer transfers page processing from one pagedirectly to the next page without making a round-trip back to theclients browser.

This provides a faster response with a little lessoverhead on the server. Transfer does not update the clientsurl history list or current url. Redirect is used to redirectthe users browser to another page or site. Discover the different step-by-step guides available for you to learn how to develop ASP. NET Core applications. Learn the basics of building an ASP. Learn about Azure Storage, and how to create applications using Azure blobs, tables, queues, and files.

Learn how you create Universal Windows apps that run on all Windows 10 devices. Write and debug your games using your game engine of choice with Visual Studio.

Build games with C through tutorials and setup instructions at the MonoGame library documentation hub. Bring AI to everyone with an end-to-end, scalable, trusted platform with experimentation and model management. Exit focus mode. Xamarin Cross-platform development Xamarin. Android Guide Xamarin. Forms Guide. These members can include constructors. NET Framework can have different classes with the same names.

Forms is the basic namespace for Windows Forms. Xml supplements those classes for working with XML. Namespaces also help avoid problems resulting from duplicate class names. Many of the early entries begin with the word Microsoft. Some of these namespaces will become an intimate part of your life. NET Framework documentation online at this page: There are three classes named Timer.

NET namespaces… so little time. Win- dows. If you open one of these namespaces in the documentation. The namespaces serve to separate the. Others are interfaces. If these classes are in different namespaces. Some are structures. For example. You can also access the. Generic contain classes that help you store inform- ation in familiar collections such as queues. Collections and System.

As the popular tee-shirt says. Besides providing all the class documentation of the. You will never. NET class library. In the Look For field. Over at the right on the bottom.

NET Framework documentation is the teaching of humility. But you can always try. In the. Select the one you want.

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You can then click the Sync With Table Of Contents button on the toolbar to get back to the Contents view and continue exploring the particular class. There is no separate pane for index results. Both Visual Studio and the. Disassemble A file containing C code generally has the filename extension. NET programmer to try it just once.

WriteLine "Hello. This is what you should use. Some information in this chapter does not apply to the. At the very least. NET Framework! In many respects. You can actually edit. Save the file from Notepad with the name firstprogram. The ldstr command loads a text string on the stack. When you run the program.

From the File Open dialog box. In Notepad. Open the First- Program class and double-click Main. Make sure that WriteLine has an initial capital and an embedded capital. On the command line. Make sure you type the words Main. C is a case-sensitive language.

From the Windows start menu. You can type FirstProgram whatever way you want or you can use a different name. Run it. I mentioned in the second chapter that a. Make sure that you type the words class. As you type. Of course. Programs written directly in CIL are just as managed and just as portable as programs written in C.

Give the project a name FirstProgram. In Visual Studio. This is an XML file that references the. In the Solution Explorer on the right. Select Code File and give the file a name of FirstProgram. You can compile and run the program by selecting Start Without Debug- ging from the Debug menu or by pressing Ctrl-F5.

A project generally creates a single executable file or a single dynamic link library. From the menu select File. A project can contain one or more C source code files. When you type System and a period. In Visual C Ex- press Edition. In either edition. Back on the command line or in Windows Explorer. In the simplest case. Now type in the program shown above.

The program will compile and run in a command-line window. Between the extremes of the command prompt and Visual Studio are other. The MSBuild program invokes the C compiler and other tools to assemble an entire executable.. Make sure the FirstProgram. You can write your own. Visual Studio has also created some intermediate files in a subdirectory of FirstProgram named obj. During compilation. NET programming tools. The MSBuild program became necessary in. You can change that class to a structure using the keyword struct: This particular program defines a class denoted by the keyword class named FirstProgram: A class can also be split between multiple files.

I generally like to restrict my C source code files to just a single class and structure. The Main method is defined with the public and static keywords: When creating this project in Visual Studio. None of these names need to be the same as the project name. In fact. Just to avoid confusion. It is common to define the class or structure with the public keyword: All code in a C program must be in either a class or a structure. There are some cases where it is required.

None of these name matches is required. In the FirstProgram class or structure is a single method named Main. The entry point to a C program is always a method named Main. But I sometimes break this rule in this book. The public keyword applied to a class is generally found much more in code that contributes to dynamic link libraries. In other words. The argument is a string literal enclosed in double-quotation marks. C can otherwise be freely formatted.

The public keyword is not actually required for the Main method. You can also define Main to have a parameter that is an array of text strings. This statement is a method call. Sometimes I use public with Main and sometimes not. The body of a method is delimited by curly brackets. If you need to break up a long string on mul- tiple lines. String literals in C are restricted to a single line. The static keyword means that this method is associated with the class itself rather than an instance of that class.

This is allowed: See the C Language Specification. The world has many more sundaes than ice cream dispensers. The entire body of this Main method is the statement: There is no instance keyword. Main can also return an integer as a termination code. A class is basically an ice cream dispenser. Although string literals must appear on one line.

If you look at the first page of the documentation for the Console class. WriteLine "Hello.. The class is prefaced with the name- space in which the class is defined. The mscorlib.

Like romance novelists. An assembly can consist of multiple files.

Where is the code for System. NET Framework generally have three names: These various versions of the WriteLine method are known as overloads. This program is functionally equivalent to the program shown earlier: The C compiler is able to establish that mscorlib. As you probably know. NET classes and structures. The C compiler will access mscorlib. As you go beyond the command line. For the command line compiler. Because the compiler is already accessing the actual DLL.

The include file provides function prototypes to the compiler. As you know. Intellisense also works by referencing mscorlib. Many of the basic classes and structures are included in mscorlib. At the time the program is run. The C compiler does not need header files. WriteLine just to display a line of text. It may seem like a big bother to type System.

You must then either explicitly or im- plicitly run a linker that accesses library files. The C compiler can determine that the WriteLine call is valid. These are known as references. WriteLine call is no longer prceded with the System name- space. WriteLine and try looking for that. This is made possible by the line near the top that begins with the keyword using. Console class can be shortened to just a capital C. The using directive only indicates a namespace.

All the sample programs from now on will have a using directive for the System namespace and occasionally other namespaces as well. A slightly different form of the using directive defines an alias that lets you decrease your repetitive typing even more.

It must appear before any type definition in the file. The using directive is not like a header file. The next step would involve defining your own short-named method that then calls WriteLine. SuperString or: In the using directive. The company name goes first. Console for any and all occur- rences of a capital C in your code. To simplify your typing. Using both SuperString clases is not a problem because both companies defined unique namespace names for their classes.

The use of this form of the using statement is primarily for a situation where you need to reference classes with the same name from two dif- ferent namespaces. Both these libraries contain a class named SuperString that is implemented entirely differently in each DLL but is useful to you in both versions. The code developed at Bovary looked something like this: The using directive does not perform a substitution of System.

Also keep in mind that C culture does not encourage the use of tech- niques like this to make your code look more obscure than it should be.. SuperString and: Most importantly. For the first couple of. I used namespaces in my program code that consisted of my name followed by the project name. NET programming books I wrote. The following program shows how you can put your own program code inside a namespace definition.. You can also use namespace definitions in your non-DLL program code.

In my recent book on the Windows Presentation Foundation. I did this for two reasons. More information about Unicode can be found at www. It consists of a bunch of characters delimited by double quotation marks. The ABCD characters stand for any 4- digit hexadecimal number. The characters are Unicode. For example: NET Framework" That is known as a string literal. The last entry in the table indicates how you can embed arbitrary Unicode characters in a character string.

Strings and the Console In the previous chapter. This allows the embedding of characters in a character string that would otherwise not be possible. WriteLine method looked like this: The following table shows the supported escape sequences with their Unicode equivalents in hexadecimal.

In the Add Reference dialog box. Show "Hello. When you click the OK button. The MessageBox. This is common with directory paths: NET Framework".

Show method displays a Windows message box with an OK button. When compiling on the command line. Forms assembly. To compile this program you need a reference to that assembly. In Visual Studio in the Solution Explorer. You can also use Unicode escape sequences in variable names. Forms namespace. If you really. In some cases you might want to encode a string literal with several backslashes.. NET tab and the System. Without the using directive. Windows Forms is a Windows client platform supported under all versions of.

The Windows Forms classes are in the System. Or select Add Reference from the Project menu. Show returns. Variable names generally begin with letters or an underscore. Until a string variable is assigned a value. You can initialize all or some of these variables: All variables must be declared before they are used. C supports a string data type for storing strings.

None of the normal escape sequences are allowed. Within a method such as Main you can declare a variable of type string using a declaration statement: You preface the first double quote with an sign: If you need to embed a double quote in the string. You can declare multiple string variables in a single declaration state- ment by separating them with commas: You can optionally initialize that string when you declare it: WriteLine will just display nothing for that string.

In either case. In the first case. WriteLine str. Or you can set the string variable to the C keyword null: WriteLine strDisplay. This code is no good: In the second case. Both Main and strDisplay are members of the class.

The program could refer to strDisplay by prefacing it with the class name: You can also declare a variable outside of Main but within the class: Notice that strDisplay is declared as static. Both strDisplay and Main are considered members of the class.

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NET Framework".. You can also declare a field but set its value in a method: This will work fine as well: WriteLine Program. You can use the same name for fields and local variables: A string field and other reference types is initialized to null.

Write "Framework! The void keyword indicates that the method returns nothing to the caller. NET ".. Write "Microsoft ". Write "Hello. Notice that the first three strings end with a space so the words are still nicely separated. Write ". If you look further in the Console documentation. This method ob- tains text typed by the user and then returns it to the program.

You can store this return value in a string variable and then later display it. Exploring the Console class further. You can rewrite the guts of FirstProgram so it looks like this: ReadLine call echos typed characters to the console but does not return until the user presses Enter.

WriteLine then prints the information in a single line. No new line is displayed and the cursor sits one space from the colon. The Console. Write call is used to display the prompt. Write and Console. Because the last line has a carriage return and line feed. WriteLine strName. WriteLine strLimerick.

Write "Type your name and press Enter: Write "Your name is ". The combination of Console. You can concatenate multiple strings using the plus operator. A string literal must appear on a single line except for verbatim strings. If you put this code at the top of Limerick. Although properties certainly resemble fields in use. The property is also static.

WriteLine Console. You might want to put a Console. ReadLine call at the bottom of the program to actually see the new title take effect. For versions 2. There is actual code being executed when you obtain or set a property. Each property has a type. This title will then appear at the top of the console window. As you can see. Title to WriteLine to display the value of the property: Within curly brackets appear the words get and set.

If you insert statements to access and change Title in the Limerick pro- gram. What on earth is ConsoleColor? If you look a little further in the System namespace documention. Using enumerations in C involves a little more typing than you may be accustomed to.

This property is intended to be appropriate for the particular environment on which the program is running. After setting the colors. As you might know. NewLine property is documented in C syntax like this: You cannot set the Environment. The Environment. If you put those Background and Foreground statements at the top of Limerick.

These two properties are also gettable and settable. The Limerick. NewLine property. Although properties have the syntax of fields. But strictly speaking. A character literal is defined with single quotation marks. There is no such thing as a signed char or an unsigned char.

The result is the same as before. You can also concatenate strings and integers. This will not work. You might try performing a calculation in the Console. Either way you can then refer to NL at the end of each line: C also defines a char type for storing a single bit Unicode character. WriteLine statement using the years in which Schubert was born and died: Or you might define NL as a field if you need it in more than one method.

You can then concatenate that variable with the string: The subtraction is now performed first and the result is concatenated with the strings..

You can declare and initialize an int like this: You can even start with the number. You can concatenate char variables with string variables or literal strings: That will display as: Schubert was 31 when he died. A simple set of parentheses around the calculation will help: String and the program will be exactly the same: That statement displays: A circle's circumference divided by its diameter is 3.

And the answer is: Something else. If you have a using directive for the System namespace. In any C program. What you cannot do is refer to the System. Because string is an alias for System. Expressing one of the two num- bers as a floating-point literal causes the other to be converted to floating point for the division.

The Math class also contains two constant fields named PI and E. How does C store strings? Notice the difference in case: The C keyword is string but the class is String. The string keyword is C is actually an alias for a class in the System namespace named String. C interprets numeric literals without decimal points as integers.

The WriteLine statement displays: One divided by three equals 0. This will work as well: Length returns the length of the string.

OLIMPIA from New Mexico
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