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Data Selection Query with Visual Basic.NET in .NET Attach PDF-417 2d barcode in .NET Data Selection Query with Visual Basic.NET




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Data Selection Query with Visual Basic.NET generate, create pdf417 none on .net projects Typical 2D QR Code Figure 4.111. The modi ed coding for the CourseList SelectedIndexChanged procedure. which is equivalent to the course name selected by the user as the project runs. D. If the TableAdapter method is selected by the user, the Fill() method is called to ll the Course table, and the FillCourseTextBox() subroutine is executed to ll ve text boxes to display the detailed course information for the course selected in the Course list box.

E. Otherwise, the DataReader method is selected. The ExecuteReader() method is executed to read back the detailed information for the selected course, and the FillCourseReaderTextBox() subroutine is called to ll that information into ve text boxes.

F. Finally, a cleaning job is performed to release objects used for this query. The two subroutines FillCourseTextBox() and MapCourseTable() have no relationship with any object used in this project; therefore, no coding modi cation is needed.

The subroutine FillCourseReaderTextBox() needs a small modi cation,. 4.18 Build an SQL Server Database Project SQLSelectRTObject Figure 4.112. The Student form window. which is to change the nomi .net vs 2010 barcode pdf417 nal argument s type from OleDbDataReader to SqlDataReader since an SQL Server data provider is utilized in this project. For the detailed line-by-line explanations of the subroutines FillCourseTextBox(), FillCourseReaderTextBox(), and MapCourseTable() (Figures 4.

87 and 4.88), refer to Section 4.17.

4. Do not forget to copy all faculty image les to the folder in which your Visual Basic executable le is located before you run this project. In this application, it is the Debug folder of the project.

. 4.18.7 Query Data Using Runtime Objects for the Student Form Now we nally come to the c visual .net pdf417 2d barcode oding for the Student form window. The Student form window is shown again in Figure 4.

112 for your convenience. The function of this form is to pick up all information related to the selected student, such as the student ID, GPA, credits, major, school year, and email, and display it in six text boxes when the Select button is clicked by the user. Also, the courses taken by that student are displayed in the Course list box.

Apparently this function needs to make two queries to two different tables, the Student and the StudentCourse tables, respectively. The coding for this form is similar to what we did for the Faculty form, with one important difference, which is the query type. In order to improve the querying ef ciency and simplify the coding, two stored procedures are developed and implemented in this section.

By using stored procedures, query coding can be signi cantly simpli ed and integrated, and the ef ciency of the data query can also be improved. Let s start with the Form Load event procedure. The coding for this event procedure is shown in Figure 4.

113.. Data Selection Query with Visual Basic.NET Figure 4.113. The coding for the Form Load event procedure. A. The namespaces of the SQ L Server data class library are imported to provide the prototypes of all data components to be created and used in this procedure. B.

A form-level text box array, StudentTextBox(), is declared and is used to hold the detailed student information as the project runs, and this information will be displayed in six text boxes in the Student form later. C. The database connection is checked before we perform any data operations between the project and the related database.

D. All sampled students names are added into the Student Name combo box, and the default student s name is the rst one in this combo box. Next, let s take a look at the coding for the Select button event procedure.

As mentioned at the beginning of this section, when this Select button is clicked by the user, six pieces of student information are displayed in six related text boxes, and the courses taken by that student are displayed in the Course list box. Two queries are needed for this operation. In order to save time and space, two stored procedures are developed for these two queries.

Let s go a little deeper into the stored procedure..
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