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How to analyze the shortcomings of the three-tier structure and three-tier structure of ASP.NET, I believe that many inexperienced people do not know what to do about it. Therefore, this paper summarizes the causes and solutions of the problems. Through this article, I hope you can solve this problem.

Description of three-tier structure of ASP.NET

The requirement of a perfect three-tier structure is to modify the presentation layer without modifying the logic layer, and modify the logic layer without modifying the data layer. Otherwise, it is difficult to say whether your application is a multi-tier structure, or whether there is a problem in the division and organization of the layer structure. Different applications have different understandings, which is just a matter of concept.

Understand the three-tier structure of ASP.NET-why should it be divided into three layers?

We use the three-tier structure mainly to make the project structure clearer and the division of labor more clear, which is conducive to later maintenance and upgrade. It does not necessarily improve performance, because the main program module can only be in a waiting state when the subroutine module is not executed. This shows that dividing the application into layers will result in some loss in its execution speed. However, from the perspective of team development efficiency, you can feel a very different effect.

It is important to note that the three-tier structure is not exclusive to .NET, nor is it a technology specifically used in databases. It is a more universal concept of architectural design.

This kind of architecture should pay attention to the relationship between tables in database design and try its best to satisfy the relationship between master and child. There should be certain restrictions on the user in terms of function, and it should not be shown that the deletion operation of the child table must be cautious, so as not to cause the foreign key of the main table to appear logically in the data of the child table without the corresponding value in the child table.

The comprehensive query method for tables is:

First query the main table and call the DL corresponding to the main table. Then query each child table according to the records of the main table. After adding the query results from the table to the main table, a large query collection is formed.

For table operations (additions, deletions and modifications):

At this point, only the main table is operated, and the operation method in the DL corresponding to the main table is called.

The RL layer is a logical fault judgment, which mainly makes a logical judgment on the incoming data on the page. Above the RL layer is UI.

How to establish a three-tier architecture solution

Create a new blank solution. Then:

"add"-"New Project"-"other projects"-"Enterprise template Project"-"C# Building Block"-"data access" (data layer, hereinafter referred to as layer D)

"add"-"New Project"-"other projects"-"Enterprise template Project"-"C# Building Block"-"Business rules" (Business layer, hereinafter referred to as C layer)

"add"-"New Project"-"other projects"-"Enterprise template Project"-"C# Building Block"-"Web user Interface" (interface layer, hereinafter referred to as U layer)

Right-click "solution"-"Project dependency", set U to depend on D and C to depend on D.

Add references D and C to U and D to C.

So far, a three-story shelf has been set up. What I said above is very specific and "stupid". People who know about it think that I am talking nonsense. In fact, I have a strong feeling that a lot of people actually do not understand this simple process at all. Although there is no objection to building two "empty projects" and one "Asp net Web application project" can also be used as a three-tier framework, and a considerable number of people think that these "enterprise template projects" are actually empty projects, which is a misunderstanding. Yes, the enterprise template project you see from solution Explorer is nothing, but you can open the project file with notepad, see the difference? There are some things behind you that you can't see, but the system is ready. In other words, if you "using System Data SqlClineit" in a class in the C layer, or use a SqlConnection object, there will be no compilation errors, but some "policy warnings" will be generated in the "Task list" warning you not to put anything that should be placed in layer D in the C layer (although the program is right, but readability and maintainability is compromised), empty projects cannot give you this function.

In the new TraceLWord3, the Enterprise template Project is applied. Put the original LWordTask.cs into a single project, which is called AccessTask. A new project named InterService is created in the solution, which contains a LWordService.cs program file, which is the "intermediate business tier" program. In order not to repeat the naming, TraceLWord3's website is placed in the WebUI project. The more complete code can be found in the CodePackage/TraceLWord3 directory--

The three-layer structure of ASP.NET: the combination of face object and reality

We know that bricks are needed to build a bridge, and bricks should be prepared before building the bridge, but in order to explain the sequence and consistency, simplicity. We first build the bridge, and in the process of building it, we need to reproduce the bricks, so that there will not be more "things that the bridge does not need". Note that in practice, bricks should be prepared first.

The U layer is actually the bridge, the C layer is brick, and the D layer is the raw material (stone, sand). This also explains why the U layer refers to and depends on the D layer (rather than the U-to-C-D level), because the bridge needs stone and sand as well as bricks.

The shortcomings of "three-tier structure"

Some netizens questioned me after reading the previous work of this article, which reminds me that the article has not mentioned the shortcomings of the "three-tier structure" so far. The word "three-tier structure" seems to be very popular all the time, perhaps because the application of this development model is more common. However, the "three-tier structure" is not a "panacea", it also has some shortcomings. Let's talk about its shortcomings.

A very obvious disadvantage of the "three-tier structure" development model is that its execution speed is not fast enough. Of course, this "execution speed" is relative to non-hierarchical applications. From the timing diagram given in this paper, this shortcoming is obviously exposed. TraceLWord1 and TraceLWord2 do not have layering, and directly call the classes provided by ADO.NET to get the data. However, TraceLWord6 does have to go through multiple calls to get the data. When the subroutine module does not return, the main program module can only be in a waiting state. So in terms of execution speed, the higher the version of the message board, the lower the ranking. The "three-tier structure" development model is not suitable for systems that are too demanding on execution speed, such as online booking, online stock speculation and so on. It is good at systems where business rules are subject to change.

The "three-tier structure" development model is difficult to get started and difficult to understand and learn. This is for beginners of programming. Software developed in this mode usually has slightly more code. This tends to drown beginners in a vast expanse of code. It is understandable that he is afraid and disgusted with it.

In fact, no matter which development mode or method, there are advantages and disadvantages. There will not be a "universal usage" that can solve any problem. So the word "three-tier structure" will not be an exception! Whether or not to use this model for system development, it is necessary to make a comparison and tradeoff. Don't abuse it!

After reading the above, have you mastered how to analyze the shortcomings of ASP.NET 's three-tier structure and three-tier architecture? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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