It will also help you leverage your knowledge of Visual Fox. Pro in. learning the basics of C#. There has been a lot of excitement generated about C#. Microsoft’s newest programming language. It’s a very clean and elegant. NET language. However, new doesn’t mean. Microsoft put C# to the test and used. NET Framework’s base classes (For the record, the . NET. Framework could have been. Visual Basic . NET. C# was chosen because most developers working on. NET Framework were C++ developers and the C# compiler was completed before. VB . NET compiler). Of all the existing programming languages, C# is the most. Java. The October, 2. Java. In this chapter. Although I will touch on basic object- oriented elements of C#. C#. and VB . NET’s object- oriented features takes place in Chapter 5, “Object. Orientation in C# and Visual Basic. NET”. For a side- by- side comparison of C#, Visual Basic. ![]() At Powerful-Sample-Resume-Formats.com, you'll find all sorts of information that can help anyone learn how to make a resume that actually gets you a job. You need tips on how to do a resume correctly, and that's what you'll. Compiler Foxpro Program Download![]() Chapter 2 Visual Studio.NET. Visual Studio.NET is the latest incarnation of Microsoft’s suite of software development tools. The VS.NET team has done a great job of providing a top-notch experience for the developer. A compiled language is a programming language whose implementations are typically compilers (translators that generate machine code from source code), and not interpreters (step-by-step executors of source code, where no pre. NET, and Visual. Fox. Pro’s operators and keywords, check out “Appendix A – Language Comparison. Tables”. For a comparison of each language’s data types, see “Appendix B – Data. Type Comparison”. Weak typing vs. Visual Fox. Pro is a weakly typed. This means that you can store a value of any type in a variable. For. example, as shown in the following code, you can store a DATETIME value in a. Visual Fox. Pro compiler. LOCAL My. Variable. My. Variable = DATETIME()My. Variable = . Second, and more importantly, weak typing allows bugs to sneak. For example, if you store an integer value in My. Compiler Foxpro Program SamplesVariable, and then. Operator/operand mismatch”. REPLACE Customer. Name WITH . What if the code never gets run until it’s. In contrast, C# is a strongly typed language (VB . NET is also. a strongly typed language, but C# is more strongly typed. See Chapter 4. “Introduction to Visual Basic . NET” for details). In the world of variables. For. example, the following code creates a date variable named My. Date, a string. variable named My. String, and an integer variable named My. Integer: Date. Time My. Date; string My. String; int My. Integer; If you do not declare the type of a variable, the C# compiler. Another common error in Visual Fox. Pro coding that causes bugs. For example, the following code. My. Variable before using it: Message. Box(. For example, if you. My. String; Message. Box. Show(My. String, . To change these lines of code. My. String: string My. String = . This aspect of strong typing is covered in Chapter 5. Object Orientation in C# and VB . I am an advocate of free software. In late 2010 I began working on a free software project (currently unreleased) called Visual FreePro. Visual FreePro was to b. Eine virtuelle Methode ist eine Methode, bei der erst zur Laufzeit ermittelt wird, welche konkrete Implementierung verwendet wird. Dieses sogenannte dynamische Binden erm. NET”. The practical value I’ve seen in my coding boils down to. Visual Fox. Pro, when I create a page worth of code, invariably there are. I can’t find those bugs until I step through the code line by line. So, you will create the obligatory “Hello World” program now. The call. to Console. Write. Line displays “Hello . NET World!” in a . NET console. application: using System; class My. First. CSharp. Program. Every C#. program must have a Main method. This method is called when the program is. Optionally, you. can specify that the Main method accept a string array parameter. If any. command- line parameters are sent when the program is executed, they are placed. System; class My. First. CSharp. Program. You will find information on these features later in this chapter. C# syntax. In this section, I’ll give you an overview of C#’s. Visual Fox. Pro’s. I’ll start out by showing you the two. C#. Case sensitivity. Visual Fox. Pro is a case- insensitive language. In. the next line, I use that variable, but I refer to it as “mystring” (all. In Visual Fox. Pro, the two names refer to the same variable. My. String = . In addition, all. If you enter a keyword with mixed case, the. Some developers have a hard time getting used to. C#’s case sensitivity. However, if you already write case- sensitive code in. Visual Fox. Pro, it’s not as big an issue. Semicolons and multi- line statements. In Visual Fox. Pro, you don’t need to put an ending. However, if a single statement continues over. Visual Fox. Pro’s. MESSAGEBOX(. As you can see by. C# statements must end. This allows a single statement to continue to the next line. For example: Message. Box. Show(. This allows you to do a mix of. In C#, all code must be contained within classes or structures. Structures are discussed in detail in Chapter 5. Object- Orientation in C# and Visual Basic . NET”. Given a choice between the. I think C#’s approach is better. VFP’s approach may be more. Grouping statements together. The convention in Visual Fox. Pro for grouping statements. For example, you group all. DEFINE CLASS and ENDDEFINE keywords. You. group code contained in class methods within PROCEDURE and ENDPROC or FUNCTION. ENDFUNC keywords: DEFINE CLASS My. Class. AS Session PROCEDURE My. Procedure ENDPROC FUNCTION My. Function ENDFUNCENDDEFINEC# uses curly braces consistently to group code together. You can also use a double. C# uses two forward slashes consistently to indicate a. For. multi- line comments, it uses a forward slash and asterisk (/*) at the beginning. Comment. Demo. See the “XML Documentation” section at the end of this chapter. Namespaces. All classes in . NET belong to a namespace. Remember. that namespaces are not a physical grouping of classes, such as a project or a. Visual Fox. Pro. They are simply a naming convention that. For example, all of the source code. HW. Net. Book. Samples. For more. information on namespaces, see Chapter 1, “Introduction to . NET”. To assign a class to a namespace, all you have to do is place. HW. Net. Book. Samples. This is different from Visual Fox. Pro, where a class is. PRG file. In Visual Fox. Pro, before you can instantiate a class, you. SET CLASSLIB or SET PROCEDURE to the class library or PRG file that. Similarly, in C#, you must specify that you. The following code specifies. System and System. Windows. Forms: using System; using System. Windows. Forms; namespace HW. Net. Book. Samples. You must explicitly declare each. The using declaration tells C# where to find. Defining a simple class. As I promised, I won’t go into too much. Here is the simplest class definition in C# (not much fat. My. First. CSharp. Class. This is necessary because the. Message. Box class belongs to this namespace. System. Windows. Forms; namespace HW. Net. Book. Samples. In the . NET world, the term. The reason I bring this up is because in the definition of. My. First. CSharp. Class, no parent or base class was specified. In C#, if you don’t specify otherwise, a class is assumed to. Object class. The Object class is the topmost class in the. NET hierarchy (the queen mother of all base classes). Every class in the . NET. Framework can trace its heritage back to the Object class. Defining class methods. You’ve already seen an example of a simple class. Here’s the official syntax for a class method. This is in keeping with C#’s strongly typed. Methods that return nothing have a return type of void. Declaring variables. Variables declared within methods are local variables. This means they are only visible within the method. Based on this, you don’t have to specify a scope (local. To declare a variable, specify its type, followed by its. Count; //. Declare an integer variable named . However, as shown in. Fields. And. Local. Vars. In addition to fields, C# classes can. Chapter 5, “Object- Orientation in. C# and Visual Basic . NET”. For now, just think of fields as variables defined. One other point to note is you can reference fields the same. You don’t need a this qualifier in. C# as you do in Visual Fox. Pro. In the previous example, you could have. Test. 1 field as this. Test. 1, but. it’s not required. After teaching a good number of C# classes, I highly recommending. Since C# is case- sensitive, using “this”. Intelli. Sense to kick in and allow you to select members from a list. If you declare a local variable with the same name as a field. For example, there are five accessibility modifiers you can apply. Table 1) that specify the visibility of a field: Table 1. Field modifiers allow you to specify the. Modifier. Descriptionpublic. Access is not restrictedinternal. Access is limited to the. Access is limited to the containing class or subclassesprotected internal. Access is limited to the current project or to subclassesprivate. Access is limited to the containing class. It’s considered good object- oriented form to declare fields as. To promote this practice, if you don’t specify a modifier, C#. If you want to allow other classes to. Properties” section in Chapter 5, “Object- Orientation in C#. Visual Basic . NET” for details). Value and reference types. NET makes a strong distinction between value types and. Value type variables store their data directly and reference type. Reference. variables are actually pointers dressed up in an object—but you can’t access. To understand this concept more clearly, you need to. C# allocates memory behind the scenes. Understanding the stack and the heap. There are two places where the . NET runtime allocates. The stack is. an area of memory used to store value types that are a fixed length. This. includes basic data types such as integers, boolean, long, float, double, and. Figure 1 provides a conceptual view of how this works. When. you declare the integer variable “x”, the runtime allocates space for the. When you assign a value to the variable, the . NET. runtime stores the value into the space it already allocated on the stack. Figure 1. When you declare a value- type variable. NET runtime allocates space for the variable on the stack. When you assign. a value to the variable, the value is stored in the space already allocated on. What happens when you copy one value variable to another. This creates two copies of the same data on the stack. When. you declare variable x it allocates space for the variable on the stack. When. you assign variable x a value of 5, it stores a 5 in the allocated space for. When you assign x to y, it allocates space for. This gives you two copies of the same data on the. The heap is an area of memory used to store reference type. When you declare a reference type. However, when you. Figure 2), rather than. Figure 2. When you declare a reference variable.
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