BİL528 – Bilgisayar Programlama II

Database Operations II

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Contents

• Adding a new record into database• Changing an existing record• Deleting a record• Displaying data from multiple tables

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3. Writing the Program

a) Adding database file into solutionb) Displaying studentsc) Adding new studentd) Changing student infoe) Deleting a studentf) Displaying all courses a student take

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c) Adding New Student

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Create a New Form “frmNewStudent”

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tbFirstName

tbLastName

calBirthDay

numAge

btnOK withDialogResult = OK

btnCancel withDialogResult = Cancel

Drag & Drop a StudentsTableAdapter object onto the form

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Double-Click OK Button and Write the Following Code

studentsTableAdapter1.Insert(tbFirstName.Text,tbLastName.Text,calBirthDay.Value,(short)numAge.Value);

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Add a Button to Main Form

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Double-Click the Button and Write the Following Code:

frmNewStudent frm = new frmNewStudent();DialogResult result = frm.ShowDialog();if (result == DialogResult.OK){ studentsTableAdapter.Fill( schoolDataSet.Students);}

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Run the Program

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Click “New Student” button, enter data, and click OK

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Some Notes

• If you close your application, make some changes in your program, build the program again, and execute the program, the last added records won’t be visible!

• This is because each time you build the project, original database file is copied into the Debug folder in your solution and all operations are made on this copy.

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d) Changing Student Info

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Create a new form “frmChangeStudent” similar to “frmNewStudent”

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Binding Data to the Controls

• In order to fill the controls, we are going to use data binding feature instead of changing contents of the controls.

• The frmChangeStudent form needs the StudentID to display the data of the selected student.

• For this purpose, create a property in frmChangeStudent form. This property will transfer student ID from main form to frmChangeStudent form.

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In the class definition, write “prop”

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Press “Tab” key two times

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The type of the property is “int” and it is ok, so press “Tab” key

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Write “StudentID” as the name of the property

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All spaces are filled, so press “Enter” key. The property is ready now!

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Binding Controls

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Select “First Name” text box. You’ll see “DataBindings” section in the Properties window

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We want to bind the Text property of the textbox, so click “Text”

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Click the arrow button on the right

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Click plus sign near “Other Data Sources”

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Click plus sign near “Project Data Sources”

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Click plus sign near “SchoolDataSet”

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Click plus sign near “Students” and click “FirstName” field

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Text is now bound and three controls have appeared

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Bind “Last Name” text box

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Bind “Value” (not “Text”) property of the calendar object

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Bind “Value” of the numeric up/down object

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Notice that a new “Fill” code has been added into the “Load” event of the form

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“FillByStudentID” instead of “Fill”

• We want to display the data of only one student.

• So, we need to use FillByStudentID method instead of Fill method.

• Delete the line and write this:this.studentsTableAdapter.FillByStudentID(

this.schoolDataSet.Students,this.StudentID);

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Load event handler of the form

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OK Button

• When the form is displayed, the data of the student is displayed on the controls.

• User changes these data and presses OK button.

• So, we need to write updating code into the Click event of the OK button.

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Updating to Database

• The modifications made by the user must be applied to the data set. This is accomplished by the EndEdit() method of the BindingSource object.

• The changes on the data set is applied to the database by the Update() method of the studentTableAdapter object.

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OK Button Click Event

• Double-click the OK button and write this code:

this.studentsBindingSource.EndEdit();this.studentsTableAdapter.Update(

this.schoolDataSet.Students);

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All Codes

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Passing Student ID

• Now, the form can display and update the data of the student whose ID is specified by the StudentID property.

• So, we need to set this property before the form is shown.

• This should be done in the main form.

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Getting the ID of the selected student

• The ID of the student selected from the DataGridView object can be obtained in two ways:

1. Get the ID from the first cell of the selected row or the DataGridView.

2. Get the ID from the binding source object.

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1. Getting ID from DataGridView

int studentID =(int)dataGridView1.SelectedRows[0].Cells[0].Value;

• In order this code to be successfully executed, you need to set MultiSelect property of the DataGridView object to False and SelectionMode property to FullRowSelect.

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2. Getting ID from Binding Source

• When a row is selected in the DataGridView object, the information about the selected row is stored in binding source object. You can get the StudentID by using this code:

DataRowView rowView = (DataRowView)studentsBindingSource.Current;

SchoolDataSet.StudentsRow row = (SchoolDataSet.StudentsRow)rowView.Row;

int studentID = row.StudentID;43

Creating the frmChangeStudent dialog and passing student ID

• Add a new button with the text “Change Student Info” into the main form.

• Write the code given in the next slide into the Click event handler of the button.

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DataRowView rowView = (DataRowView)studentsBindingSource.Current;

SchoolDataSet.StudentsRow row = (SchoolDataSet.StudentsRow)rowView.Row;

int studentID = row.StudentID;

frmChangeStudent frm = new frmChangeStudent();frm.StudentID = studentID;DialogResult result = frm.ShowDialog();

if (result == DialogResult.OK){ // Update the DataGridView: this.studentsTableAdapter.Fill(this.schoolDataSet.Students);}

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Run the program, select a student, and click “Change Student” button

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The student info is displayed:

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Change values and click OK

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The data has been changed!

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e) Deleting a Student

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Add a “Delete Student” button into the main form

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Double-click the button and write the following code:

// Get the selected row:DataRowView rowView =

(DataRowView)studentsBindingSource.Current;SchoolDataSet.StudentsRow row =

(SchoolDataSet.StudentsRow)rowView.Row;

// Delete the student:this.studentsTableAdapter.Delete(row.StudentID, row.FirstName,

row.LastName, row.BirthDay, row.Age);

// Update DataGridView:this.studentsTableAdapter.Fill(schoolDataSet.Students);

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f) Displaying All Courses a Student Take

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Add a “Display Courses” button into the form

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Create a new form “frmStudentCourses”

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Select “Courses” as the Data Source of the DataGridView object

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Click “Add Query…” command of coursesTableAdapter object

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Write “FillByStudentID” into the query name box and click “Query Builder”

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Right-Click on the empty area and select “Add Table…” command

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Select both Enrolment and Students tables and click Add button

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Tables are displayed in Query Builder, click Close button

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Tables are automatically joined on CourseID and StudentID fields

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Scroll down to an empty “Column” cell and select “Students.StudentID”

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Go to the “Filter” column and write “=?”

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Go to the “Output” column and clear the check box

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If you wish, you can execute the query. Click OK to return to the previous window

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Click OK to return to the program

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Select the toolstrip and delete it

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Go to the code view and add a property named StudentID

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Go to the Load event of the form and change the code

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Go back to the main form and double-click “Display Courses” button

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Write this code into the Click event

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Execute the program, select a student, and click “Display Courses”

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Courses taken by the student are displayed but first and last names of the student are missing!

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Select “First Name” label and bind its Text to “FirstName” field as shown below

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Select “Last Name” label and bind its Text to “LastName” field as shown below

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Go to the Load event and change Fill method to FillByStudentID method

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Execute the program, select a student, and click “Display Courses”

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First and last names of the student are successfully displayed now!

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