[IDC Charging System] Summary

Before every giant thing came, I had to retreat unconsciously. This time, I think of myself as Altman.

Naming Convention document

This is the first example. With the standard, you can see its name and meaning.

Database Design

After knocking on the three-tier Login Demo, I started to design the database from the ERTU. I flipped through the self-examination books, and drew out the entities that may be drawn out from the data room charging system and started to contact each other. Convert to a logical structure. The table and primary key may change slightly depending on the business. For example, whether a student is allowed to have multiple cards, whether the original card number can be re-registered after the card is returned, whether to delete records, and so on to modify or add some auxiliary marking fields, there are also some other problems involved, such as adding a user who adds the user and so on. It basically follows the three paradigm, and then comes up with some views that involve multiple tables.

 

Drawing

After that, how can I abstract the factory and ing at the beginning? Why did you hear that there is still an appearance? What is sqlhelper? Although everyone said that this kind of information on the Internet is a huge basket, but I always feel that I should try to add it myself after learning the design model. After a while, I couldn't help myself, and I was in a bad mood. The master gave guidance twice before he began to change his mind and began to stand on the shoulders of giants. At this stage, I began to learn how to use EA and began to understand the cooperation between different layers. Check online to see how people learn and understand it. The appearance is divided by function, and Other types are classified by table. When the BLL layer was started, this view class was added, indicating that it was not accessible at the time.

Implementing

Sqlhelper has used the abstract factory and appearance that I have heard before to implement a 7-layer architecture. I used breakpoint debugging to solve the problem. Think about it. Layer 7 is nothing more than Layer 3. When it comes to new usage, you need to check the internet, but similar functions become more and more understandable.

The implementation was not smooth sailing, but there were a lot of errors, just like when the database was originally used. Now, I can't mix myself any more.

 

About object transfer or others

 

At the beginning, I heard that datatable is not allowed. So I first used datatable for a demo before I typed it. It is also a preliminary understanding of the decoupling that makes it inconvenient for each layer to call each other. Later, I focused on understanding object transfer. At present, between layers, Boolean is returned, and datatable can be converted to list by referring to others.

When querying a view and returning the attributes of two or more objects, consider the following methods.

I. do not need to worry about

Is to query separately, and then assign them to each object. It's just code.

2. Create a union entity class. An attribute contains all attributes of two basic entities. I think, if C ++ is used, it is not a waste of trouble to come up with multiple inheritance. However, VB.net does not support wow.

3. As Chao told me, you can change the parameter to byref. Returns an object that implicitly transmits another object attribute. Or simply implicitly upload two entities.

However, I still don't know how to solve this problem. For example, when I register the student ID, I can determine whether the student ID exists and whether the card number exists, then I will return 3 medium cases. This will return an integer, isn't it appropriate? If two object types are returned, is the appearance redundant?

 

 

About Databases

 The database field does not correspond to the object attribute.

In the query statement, you can add a small name to the database field. For example, select username as strusername

 

"The object is not set to reference the instance of the object ."

First, let's see if it prompts whether the types except interfaces do not use "new" when instantiating. In another case, let's see if the database operation statements can be operated in the database. (Of course, if the most common problem persists, add a breakpoint to the object class and check whether the conversion from datatable to list is wrong .)

 

Must declare a scalar variable

Queries fields that do not exist in the database.

 

Truncation character

Because the data in the database exceeds the defined space size

Small experience

It is interesting to set a power failure.

You are advised to re-compile the modified file. Otherwise, the pre-modification solution is executed.

For example, a reference to a non-shared Member requires an object reference. It is also very common.

Later, I tried to generate entity code in EA. At least a little less repetitive work.

 

* ************************************* Data center in progress, summary is being accumulated. To be continued *************************************

However, I often struggle and feel that it is too difficult to take the ready-made products directly. Later, after talking with other students, I changed my thoughts at that time. At this stage, I began to imitate and understand what I was doing. Is that the case?