Shulou(Shulou.com)06/02 Report--

In this issue, the editor will bring you about how to analyze the joint structure in .NET. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

The federated structure in .NET is described below.

When programming in C language for some algorithms, several different types of variables need to be stored in the same memory unit. That is, using the overlay technique, several variables cover each other. This kind of structure in which several different variables occupy a section of memory together is called "common body" type structure in C language, which is called common body for short, also called union.

In C++, there is a type called consortium (also called Commons). Its keyword is union, which is very similar to structural struct in use. It can contain any structural type data, but it also has a very unique feature, that is, all data points to one address.

All the data in the consortium refers to the data at the same address in a memory block, and when we change the value of any kind of data in the consortium, the values of the other data will change accordingly.

This is very effective for unknown types of data, you can use a union to load a data and then analyze whether its data is valid, or you can perform bit operations on some special types to get the value of its particular location. Www.yzjxsp.com

But in VB.NET or C#, there is no union keyword to make us famous for a consortium, but what can we do to become a consortium?

This requires the use of structural attributes!

Let's take a look at how to convert the following C++ consortium code into a VB.NET federation structure!

Union myunion {char b; / / a single-byte integer that represents a single-byte integer short s using the char type in the c language; / / a double-byte integer www.liuhebao.com int I; / / a four-byte integer}

The size of the consortium is 4 bytes, and each of its data is represented as single-byte, double-byte, and four-byte integers respectively. Any change in its data during operation will affect other data.

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Structure attributes are introduced to accurately control the position of elements in the structure.

_ Structure MyUnion 'sets the offset value of the field. Set it to 0 to Dim b As Byte' single-byte integer Dim s As Short 'double-byte integer Dim i As Integer' four-byte integer End Structure www.yzyedu.com

This is the way to set up the federated structure in .NET, and the setting method in C# is the same as in VB.NET, so I won't repeat it here.

Let's introduce the application of the characteristics of the consortium. Take the structure of the consortium that we have just known as an example, the following code will demonstrate the characteristics of the consortium:

Dim MU As New MyUnion MsgBox (String.Format ("{0} {1} {2}", MU.b, MU.s, MU.i)) '000 MU.s = Int16.MaxValue MsgBox (String.Format ("{0} {1} {2}", MU.b, MU.s, MU.i))' 255 32767 32767 MU.b = 12 MsgBox (String.Format ("{0} {1} {2}", MU.b, MU.s) MU.i)'12 32524 32524 MU.i = 0 MsgBox (String.Format ("{0} {1} {2}", MU.b, MU.s, MU.i))'0 0

The above code can more visually show the changes of the data in memory, and whenever the federated data is changed, the other data will also change with the change of memory.

Of course, there are limitations to using unions, that is, .NET unions only apply to value types and cannot be applied to reference types and pointers, and you cannot set strings (String) or arrays into union types, which requires great attention!

Of course, the union structure in .net is not just the above usage, you can use your imagination, such as:

_ Structure MyUnion2 www.jokedu.com Dim b1 As Byte Dim b2 As Byte Dim b3 As Byte Dim b4 As Byte Dim i As Integer Dim ui As UInteger End Structure

This structure can get each byte of a signed or unsigned four-byte integer without having to write its own algorithm to analyze it.

Test the code:

Code:

Dim MU As MyUnion2 MsgBox (MU.i & ":" & MU.ui)'0: 0 MsgBox (String.Format ("{0} {1} {2} {3}", Hex (MU.b1), Hex (MU.b2), Hex (MU.b3)) Hex (MU.b4) '000 MU.b1 = 255: MU.b2 = 255: MU.b3 = 255: MU.b4 = 255MsgBox (String.Format ("{0} {1} {2} {3}", Hex (MU.b1), Hex (MU.b2), Hex (MU.b3)) Hex (MU.b4)'FF FF FF FF MsgBox (MU.i & ":" & MU.ui)'- 1: 4294967295 this is what the editor shares with you about how to analyze the federated structure in .NET. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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