The Typed DataSet itself consists of classes that extend the ADO.NET DataSet, DataTable, and DataRow classes. Figure 4 diagrams the situation: Figure 4 – Business objects assembly references the DAL, so the DAL has no concept of business objects. To add a new method to the DAL, return to the DataSet Designer, right-click in the ProductsTableAdapter section, and choose Add Query. Microsoft created the DataSet class specifically for storing relational information in a non-database specific data structure, so the DataSet comes highly recommended for returning query information containing multiple records and or tables of data. The DataTable's role is to serve as the strongly-typed objects used to pass data between the layers. Right-click on the GetProducts() method in the ProductsTableAdapter and choose Configure. Layered application designs are extremely popular because they increase application performance, scalability, flexibility, code reuse, and have a myriad of other benefits that I could rattle off if I had all of the architectural buzzwords memorized. Figure 17: Choose the Names for the TableAdapter Methods (Click to view full-size image). The steps for adding the Northwind database to the Server Explorer depend on whether you want to use the SQL Server 2005 Express Edition database in the App_Data folder or if you have a Microsoft SQL Server 2000 or 2005 database server setup that you want to use instead. ASP.NET Core is a new web framework that Microsoft built on top of .NET Core to shed the legacy technology that has been around since .NET 1.0. A Typed DataSet is a class generated for you by Visual Studio based on a database schema and whose members are strongly-typed according to this schema. This approach tightly couples the data-access logic with the presentation layer. To do so, simply pass business object properties into the DAL via native .NET type method parameters. This will bring up the Add Connection dialog box, where you can specify the server to connect to, the authentication information, and the database name. Figure 6 depicts a DAL broken down into three individual data service classes: Figure 6 – Breaking down the DAL into multiple data service classes. To examine or modify any of these database command properties, click on the CommandText subproperty, which will bring up the Query Builder. So it’s always a good idea to make sure you have a good grasp on the fundamentals. ), Figure 23: The TableAdapter has InsertCommand, UpdateCommand, and DeleteCommand Properties (Click to view full-size image). When working with data one option is to embed the data-specific logic directly into the presentation layer (in a web application, the ASP.NET pages make up the presentation layer). Figure 9: Create the Query Graphically, through the Query Editor (Click to view full-size image). On the next screen the InsertCommand's CommandText appears. To begin creating our DAL, we start by adding a Typed DataSet to our project. In the next tutorial we'll define a number of business rules and see how to implement them in a separate Business Logic Layer. For our Products DataTable, the TableAdapter will contain the methods GetProducts(), GetProductByCategoryID(categoryID), and so on that we'll invoke from the presentation layer. Since business objects cannot store data indefinitely, the business tier relies on the data tier for long term data storage and retrieval. After updating the GetProducts() method to use this new query the DataTable will include two new columns: CategoryName and SupplierName. Jürgen Gutsch - 15 January, 2019. REST API concepts and examples - … We'll use strongly-typed DataSets for these tutorials' architecture. If you access tables directly in the business layer, then you are forced to update your business tier to account for the changes to the table. If checked, the final checkbox, "GenerateDBDirectMethods," creates Insert(), Update(), and Delete() methods for the TableAdapter. Your only real option is to make a complete copy of the business object code so you can update the data access logic in it to support SQL Server. You also see sub-layers in the data tier with database systems. Up until now, we've only looked at working with a single TableAdapter for a single database table. As mentioned previously, the method parameters and return values in the DAL are all database independent to ensure your business objects are not bound to a particular database. After the wizard closes we are returned to the DataSet Designer which shows the DataTable we just created. He is also a blogger and author of Pro ASP.NET 2.0 Website Programming and SharePoint 2013 Essentials for Developers. To get started defining the SQL query we must first indicate how we want the TableAdapter to issue the query. In either case, this approach tightly couples the data access logic with the presentation layer. The @CategoryID parameter indicates to the TableAdapter wizard that the method we're creating will require an input parameter of the corresponding type (namely, a nullable integer). To accomplish this, go to the File menu and choose New Web Site, displaying the New Web Site dialog box. A database placed in the App_Data folder is automatically added to the Server Explorer. You can expand the database node to explore its tables, views, stored procedures, and so on. In other words, your application has the means to support two databases. The Data Access Layer is the database server that manages the database, such as Microsoft SQL Server or Oracle. His latest book is Sams Teach Yourself ASP.NET 2.0 in 24 Hours. If you use a different SQL Server version of the Northwind database, you will need to update the NORTHWNDConnectionString setting in the application's Web.config file. As business object changes arise, you have to make those changes to both the SQL Server code base and the Oracle code base. All code that is specific to the underlying data source such as creating a connection to the database, issuing SELECT, INSERT, UPDATE, and DELETE commands, and so on should be located in the DAL. In N Layer Architecture, the Database is usually the Core of the Entire Application, i.e It is the only layer that doesn’t have to depend on anything else. Your Angular components, their templates, and the models you define in your Angular app are all presentation layer artifacts. However, by exposing an IDataReader, IDBCommand, or IDataParameter object you do not tie yourself to particular database so they are an acceptable option, though not my first choice. Since the total number of data access methods in your DAL can get fairly large fairly quickly, it helps to separate those methods out into smaller more manageable Data Service Classes (or partial classes in .NET 2.0) inside your DAL. Pure academics will tell you that the DAL should be “data-source independent” and not just “database independent” so be prepared for that fight if you have a Harvard or Oxford grad on your development team who majored in theoretical application design. And since the DAL uses database-specific code, what’s the benefit? Database specific objects such as SqlDataReader, SqlCommand, and SqlParameter are tied to SQL Server, and exposing them from the DAL would defeat the purpose. Layered application designs are extremely popular because they increase application performance, scalability, flexibility, code reuse, and have a myriad of other benefits that I could rattle off if I had all of the architectural buzzwords memorized. Presented with the same challenge of making the switch from Oracle to SQL Server, you can just make a copy of the Oracle DAL and then convert it to work with SQL Server. In this article you will explore a key component of application architecture known as the Data Access Layer (DAL), which helps separate data-access logic from your business objects. With this pattern a developer deletes, inserts, and modifies the DataRows in a DataTable and then passes those DataRows or DataTable into an update method. Figure 10: Select Only the Generate Insert, Update, and Delete statements Option (Click to view full-size image). These objects can be used to access a list of all products from code like: This code did not require us to write one bit of data access-specific code. How to create SQL Data Access Layer in C# using ADO.NET – Part 2 1. And best of all the DataTables returned by the TableAdapter can be bound to ASP.NET data Web controls, such as the GridView, DetailsView, DropDownList, CheckBoxList, and several others. If, for example, you have a Person class then you may need data access methods like Person_GetAll, Person_GetPersonByID, Person_GetByLoginCredentials, Person_Update, Person_Delete, and so on, so you can do everything you need to do with a Person object via the DAL. In the classic three tier design, applications break down into three major areas of functionality: Inside each of these tiers there may also exist a series of sub-layers that provide an even more granular break up the functional areas of the application. The business layer maintain… Figure 3 depicts separating data access logic out into a separate DAL: Figure 3 – Business objects with separate data access layer. asp.net - Use classic C# Class Library to service as Data Access Layer for multiple platforms - Stack Overflow Use classic C# Class Library to service as Data Access Layer for multiple platforms Furthermore, you'll manually have to provide the InsertCommand, UpdateCommand, and DeleteCommand property values if you want to use the batch updating pattern. Implementing these patterns can help insulate your Application from the changes in the data store and can facilitate automated unit testing or test-driven development (TDD). Once you have the database installed, go to the Server Explorer in Visual Studio, right-click on the Data Connections node, and choose Add Connection. Looking at the previous code example, without IntelliSense's help it's not particularly clear what Products table column maps to each input parameter to the Update() and Insert() methods. With the web site created, the next step is to add a reference to the database in Visual Studio's Server Explorer. Of course, you also deal with non-relational information when you pass data back and forth between your business objects and the DAL. To access a particular column from a loosely-typed DataTable we need to use syntax like: DataTable.Rows[index]["columnName"]. If you want to do sorting in gridview then you can handle it at page level specifically at gridview events. A business object is a component that encapsulates the data and business processing logic for a particular business entity. The benefits of this layered architecture are well documented (see the "Further Readings" section at the end of this tutorial for information on these advantages) and is the approach we will take in this series. Let's leave this checkbox selected. Before we can create our Data Access Layer (DAL), we first need to create a web site and setup our database. Rather, the ORM is an abstraction layer from the DAL to the data source. Figure 3: All Data Access Code is Relegated to the DAL (Click to view full-size image). Furthermore, getting data out of the DataSet is fairly easy because it contains methods for extracting your data as tables, rows, and columns. A Typed DataSet serves as a strongly-typed collection of data; it is composed of strongly-typed DataTable instances, each of which is in turn composed of strongly-typed DataRow instances. Furthermore, a couple of the 35+ tutorials will utilize certain database-level features that aren't supported by Access. Figure 22: All Changes are Synchronized with the Database When the Update Method is Invoked (Click to view full-size image). We can augment the TableAdapter's initial method, GetProducts(), to include both the CategoryName and CompanyName column values, which will update the strongly-typed DataTable to include these new columns as well. When creating the first method in the TableAdapter you typically want to have the query return those columns that need to be expressed in the corresponding DataTable. Figure 21: Each Insert, Update, and Delete Request is Sent to the Database Immediately (Click to view full-size image). By default, insert methods issue non-query methods, meaning that they return the number of affected rows. Figure 28: Change the ExecuteMode Property to Scalar (Click to view full-size image). Figure 6: Save the Connection String to Web.config (Click to view full-size image). This is called data access logic. While being able to work with all products is definitely useful, there are times when we'll want to retrieve information about a specific product, or all products that belong to a particular category. Figure 24: Configure the INSERT, UPDATE, and DELETE Statements in the Query Builder (Click to view full-size image). Another pattern is to include the data-access logic directly in the ASP.NET pages (the presentation layer). After completing the wizard, the DataSet Designer includes the new TableAdapter methods. Copyright 1999 - 2020 Red Gate Software Ltd. Figure 5: Choose the Northwind Database from the Drop-Down List (Click to view full-size image). You can write everything in code behind the page. 2:56. Another option for passing information, and the one that I gravitate towards because of its flexibility, is the DataSet. There may be times when we only want to update a single column or two, or want a customized Insert() method that will, perhaps, return the value of the newly inserted record's IDENTITY (auto-increment) field. The other pattern, which I'll refer to as the batch update pattern, is to update an entire DataSet, DataTable, or collection of DataRows in one method call. These two steps are accomplished simultaneously by creating a query that returns the columns from the table that we want reflected in our DataTable. And of course, this brings us to the topic of business objects and the Data Access Layer (also known as the DAL), two sub-layers within the business tier. Any time a business object needs to access the data tier, you use the method calls in the DAL instead of calling directly down to the data tier. Getting Started with Onion Architecture If you did not add the Northwind database to the Server Explorer, you can click the New Connection button at this time to do so. Not fun. Designers don’t have to worry about messing up code to make user interface changes, and developers don’t have to worry about sifting through the user-interface to update code. If you opt to save the connection string in the configuration file it's placed in the
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