Presentation business data access layer and foxpro

Aug 08,

Presentation business data access layer and foxpro

presentation business data access layer and foxpro

Summary Introduction As Web developers, our lives revolve around working with data. We create databases to store the data, code to retrieve and modify it, and web pages to collect and summarize it.

This is the first tutorial in a lengthy series that will explore techniques for implementing these common patterns in ASP. NET pages that share a common page layout. These tutorials are geared to be concise and provide step-by-step instructions with plenty of screen shots to walk you through the process visually.

Each tutorial is available in C and Visual Basic versions and includes a download of the complete code used. This first tutorial is quite lengthy, but the rest are presented in much more digestible chunks. The web application was built using Visual Studio Professional Edition as a file system-based Web site project.

However, all of the tutorials will work equally well with the free version of Visual StudioVisual Web Developer. The tutorials after the third one will build upon the foundation laid in the first three. Start by creating a new file system-based ASP.

By adding a database to the Server Explorer you can add tables, stored procedures, views, and so on all from within Visual Studio. You can also view table data or create your own queries either by hand or graphically via the Query Builder.

While we can provide this connection information at that point in time, Visual Studio automatically populates a drop-down list of the databases already registered in the Server Explorer.

MDF in the Server Explorer, which you can expand and explore its tables, views, stored procedure, and so on see Figure 2. 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.

Once you have successfully configured the database connection information and clicked the OK button, the database will be added as a node underneath the Data Connections node. You can expand the database node to explore its tables, views, stored procedures, and so on.

Creating the Data Access Layer 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.

Creating A Web Site

This may take the form of writing ADO. In either case, this approach tightly couples the data access logic with the presentation layer.

The recommended approach, however, is to separate the data access logic from the presentation layer. 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.

The presentation layer should not contain any references to such data access code, but should instead make calls into the DAL for any and all data requests. Data Access Layers typically contain methods for accessing the underlying database data. The Northwind database, for example, has Products and Categories tables that record the products for sale and the categories to which they belong.

In our DAL we will have methods like: GetCategorieswhich will return information about all of the categories GetProductswhich will return information about all of the products GetProductsByCategoryID categoryIDwhich will return all products that belong to a specified category GetProductByProductID productIDwhich will return information about a particular product These methods, when invoked, will connect to the database, issue the appropriate query, and return the results.

How we return these results is important. These methods could simply return a DataSet or DataReader populated by the database query, but ideally these results should be returned using strongly-typed objects.

presentation business data access layer and foxpro

A strongly-typed object is one whose schema is rigidly defined at compile time, whereas the opposite, a loosely-typed object, is one whose schema is not known until runtime. For example, the DataReader and the DataSet by default are loosely-typed objects since their schema is defined by the columns returned by the database query used to populate them.A data access layer follows the idea of "separation of concerns" whereby all of the logic required for your business logic to interact with your data layer (database) is isolated to a single set of classes (layer).

Between business layer and data layer you should have a similar separation. The data layer is responsible for getting the data you want from some storage location (database, CSV file, web service, ).

Again, ideally, the business layer should not depend on the implementation details of the data layer. Aug 10,  · It also means any business object can get and store basket items via the data access layer, and if your tables change in some way you just update your data access layer and as all your business objects use .

Presentation Layer The last but not the least layer presentation business data access layer design the pattern is the Presentation Layer. A middle dynamic content processing and generation level application server e.

The data access layer enforces rules regarding the storage and access of information. For example: dates must be valid dates and numeric fields must never contain alphanumeric characters. This diagrams is a "logical" representation of an application system. Dec 20,  · hello everyone i have got a problem i want to design business layer, data access layer, presentation layer for using, can anyone help me to.

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