how to generate qr code in asp.net using c# 'Plane.Identifier' is inaccessible due to its protection level in C#

Make QR Code JIS X 0510 in C# 'Plane.Identifier' is inaccessible due to its protection level

'Plane.Identifier' is inaccessible due to its protection level
QR Creation In C#
Using Barcode creator for .NET framework Control to generate, create QR Code JIS X 0510 image in .NET framework applications.
www.OnBarcode.com
Read QR Code In C#
Using Barcode recognizer for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
What s that all about
Painting Data Matrix In Visual C#.NET
Using Barcode creation for Visual Studio .NET Control to generate, create ECC200 image in Visual Studio .NET applications.
www.OnBarcode.com
UCC - 12 Creation In C#
Using Barcode creation for Visual Studio .NET Control to generate, create UCC - 12 image in VS .NET applications.
www.OnBarcode.com
Protection Levels
Matrix 2D Barcode Maker In C#.NET
Using Barcode maker for .NET Control to generate, create 2D Barcode image in .NET framework applications.
www.OnBarcode.com
Encode GS1 128 In C#
Using Barcode printer for .NET framework Control to generate, create GS1 128 image in VS .NET applications.
www.OnBarcode.com
Earlier, we mentioned that one of the objectives of good design is encapsulation: hiding the implementation details so that other developers can use our objects without relying on (or knowing about) how they work. As the error we just saw in Example 3-3 shows, a class s members are hidden by default. If we want them to be visible to users of our class, we must change their protection level. Every entity that we declare has its own protection level, whether we specify it or not. A class, for example, has a default protection level called internal. This means that it can only be seen by other classes in its own assembly. We ll talk a lot more about assemblies in 15. For now, though, we re only using one assembly (our example application itself), so we can leave the class at its default protection level. While classes default to being internal, the default protection level for a class member (such as a property) is private. This means that it is only accessible to other members of the class. To make it accessible from outside the class, we need to change its protection level to public, as Example 3-4 shows.
Generate EAN-13 Supplement 5 In C#
Using Barcode maker for .NET Control to generate, create EAN-13 image in VS .NET applications.
www.OnBarcode.com
Draw UCC - 14 In C#.NET
Using Barcode drawer for Visual Studio .NET Control to generate, create UPC Case Code image in VS .NET applications.
www.OnBarcode.com
class Plane { public string Identifier {
QR Code ISO/IEC18004 Drawer In None
Using Barcode creator for Online Control to generate, create QR Code image in Online applications.
www.OnBarcode.com
Make QR In Visual C#
Using Barcode printer for .NET framework Control to generate, create QR Code image in Visual Studio .NET applications.
www.OnBarcode.com
}
Creating Barcode In Objective-C
Using Barcode maker for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
Painting ECC200 In VS .NET
Using Barcode drawer for .NET Control to generate, create DataMatrix image in .NET framework applications.
www.OnBarcode.com
}
EAN 128 Maker In None
Using Barcode creation for Office Word Control to generate, create GS1-128 image in Microsoft Word applications.
www.OnBarcode.com
Drawing UCC-128 In Java
Using Barcode maker for Java Control to generate, create UCC - 12 image in Java applications.
www.OnBarcode.com
get; set;
Scanning Data Matrix In VB.NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Data Matrix Drawer In Java
Using Barcode generator for BIRT Control to generate, create ECC200 image in BIRT applications.
www.OnBarcode.com
Now when we compile and run the application, we see the correct output:
Decoding Code 128 Code Set C In .NET
Using Barcode reader for .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Drawing GS1 DataBar Stacked In Visual Studio .NET
Using Barcode encoder for .NET Control to generate, create GS1 DataBar Limited image in Visual Studio .NET applications.
www.OnBarcode.com
Your plane has identifier BA0049
Make Barcode In None
Using Barcode printer for Software Control to generate, create Barcode image in Software applications.
www.OnBarcode.com
Draw Barcode In None
Using Barcode creation for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Notice how this is an opt-in scheme. If you don t do anything to the contrary, you get the lowest sensible visibility. Your classes are visible to any code inside your assembly, but aren t accessible to anyone else; a class s properties and methods are only visible inside the class, unless you explicitly choose to make them more widely accessible. When different layers specify different protection, the effective accessibility is the lowest specified. For example, although our property has public accessibility, the class of which it is a member has internal accessibility. The lower of the two wins, so the Identifier property is, in practice, only accessible to code in the same assembly. It is a good practice to design your classes with the smallest possible public interface (part of something we sometimes call minimizing the surface area ). This makes it easier for clients to understand how they re supposed to be used and often cuts down on the amount of testing you need to do. Having a clean, simple public API can also improve the security characteristics of your class framework, because the larger and more complex the API gets, the harder it generally gets to spot all the possible lines of attack. That being said, there s a common misconception that accessibility modifiers secure your class, by preventing people from accessing private members. Hence this warning:
It is important to recognize that these protection levels are a convenient design constraint, to help us structure our applications properly. They are not a security feature. It s possible to use the reflection features described in 17 to circumvent these constraints and to access these supposedly hidden details.
To finish this discussion, you should know that there are two other protection levels available to us protected and protected internal which we can use to expose (or hide) members to developers who derive new classes from our class without making the members visible to all. But since we won t be talking about derived classes until 4, we ll defer the discussion of these protection levels until then. We can take advantage of protection in our Plane class. A plane s identifier shouldn t change mid-flight, and it s a good practice for code to prevent things from happening that we know shouldn t happen. We should therefore add that constraint to our class. Fortunately, we have the ability to change the accessibility of the getter and the setter individually, as Example 3-5 shows. (This is one reason the property syntax makes use declare the get and set explicitly it gives us a place to put the protection level.)
class Plane { public string Identifier { get; private set; } }
Compiling again, we get a new error message:
The property or indexer 'Plane.Identifier' cannot be used in this context because the set accessor is inaccessible
The problem is with this bit of code from Example 3-3:
someBoeing777.Identifier = "BA0049";
We re no longer able to set the property, because we ve made the setter private (which means that we can only set it from other members of our class). We wanted to prevent the property from changing, but we ve gone too far: we don t even have a way of giving it a value in the first place. Fortunately, there s a language feature that s perfect for this situation: a constructor.
Copyright © OnBarcode.com . All rights reserved.