Binding the DetailsView to a SqlDataSource

Binding the DetailsView to a SqlDataSource

Here, our aim is to replicate the functionality the DetailsView gave us in Chapter 11, and to add functionality that will allow users to add and delete employees’ records.

Let’s start by adding another SqlDataSource control, either next to or below the existing one, in AddressBook.aspx. Give the new SqlDataSource the name employeeDataSource. Click its smart tag, and select Configure Data Source. The Configure Data Source wizard will appear again.

In the first screen, choose the Dorknozzle connection string. Click Next, and you’ll be taken to the second screen, where there’s a bit more work to do. Start by specifying the Employees table and checking all of its columns, as shown in Figure 12.9.

Figure 12.9. Choosing fields

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Figure 12.10. Creating a new condition

Next, click the WHERE… button. In the dialog that opens, select the EmployeeID column, specify the = operator, and select Control in the Source field. For the

Control ID select grid, and leave the default value empty, as Figure 12.10 shows.

Finally, click Add, and the expression will be added to the WHERE clause list. The SQL expression that’s generated will filter the results on the basis of the value selected in the GridView control. Click OK to close the dialog, then click the Advanced… button. Check the Generate INSERT, UPDATE, and DELETE statements checkbox, as shown in Figure 12.11.

Click OK to exit the Advanced SQL Generation Options dialog, then click Next.

In the next screen, feel free to click on Test Query to ensure everything’s working as expected. If you click Test Query, you’ll be asked for the Employee ID’s type and value. Enter 1 for the value, leave the type as Int32, then click OK. The row should display as shown in Figure 12.12.

Click Finish.

Congratulations! Your new SqlDataSource is ready to fill your DetailsView.

Next, we need to tie this SqlDataSource to the DetailsView and specify how we want the DetailsView to behave. Open AddressBooks.aspx, locate the DetailsView control and set the properties as outlined in Table 12.2.

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Binding the DetailsView to a SqlDataSource

Figure 12.11. Generating INSERT, UPDATE, and DELETE statements

Figure 12.12. Testing the query generated for our data source

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Table 12.2. Properties to set for the DetailsView control

Property	Value
AutoGenerateDeleteButton	True
AutoGenerateEditButton	True
AutoGenerateInsertButton	True
AllowPaging	False
DataSourceID	employeeDataSource
DataKeyNames	EmployeeID

Recreating the Columns

If you’re using Design View, make sure you choose Yes when you’re asked about recreating the DetailsView rows and data keys. If you’re not using Design View, set the columns as shown here:

File: AddressBook.aspx (excerpt)

<Fields>

<asp:BoundField DataField="EmployeeID" HeaderText="EmployeeID" InsertVisible="False" ReadOnly="True" SortExpression="EmployeeID" />

<asp:BoundField DataField="DepartmentID" HeaderText="DepartmentID" SortExpression="DepartmentID" />

<asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />

<asp:BoundField DataField="Username" HeaderText="Username" SortExpression="Username" />

<asp:BoundField DataField="Password" HeaderText="Password"

SortExpression="Password" />

<asp:BoundField DataField="MobilePhone" HeaderText="MobilePhone" SortExpression="MobilePhone" />

</Fields>

You’re ready! Execute the project, and enjoy the new functionality that you implemented without writing a single line of code! Take it for a quick spin to ensure that the features for editing and deleting users are perfectly functional!

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Binding the DetailsView to a SqlDataSource

Right now, when we add a new employee, the form looks like the one shown in Figure 12.13.

Figure 12.13. Adding a new employee

Adding Users the Easy Way

If you want to be able to add new employees through this form, the easiest way to do so is to leave in all the required columns; otherwise, you’ll get an error when you try to add a new employee without specifying values for the NOT NULL columns. If you don’t need inserting features, and you want to keep the list of details short, you can simply remove the unwanted columns from the list.

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Before we discuss exactly what’s happening here, and how the functionality works, let’s implement a few small improvements.

If you agreed to let Visual Web Developer generate the DetailsView columns for you, it will automatically have rewritten the templates we developed in the last chapter, and added BoundField controls for each of the columns you’re reading from the data source.

The HeaderTemplate is still intact, but we want to update it to show a different display when we’re inserting details for a new employee. Currently, the header is set to display the Name field of the selected employee, which means it will be empty when we insert a new employee (as you could see in Figure 12.13). To change this, modify the HeaderTemplate of your DetailsView as follows:

Visual Basic

File: AddressBook.aspx (excerpt)

<HeaderTemplate>

<%#IIf(Eval("Name") = Nothing, "Adding New Employee", _ Eval("Name"))%>

</HeaderTemplate>

C#	File: AddressBook.aspx (excerpt)

<HeaderTemplate>

<%#Eval("Name") == null ? "Adding New Employee" : Eval("Name")%>

</HeaderTemplate>

IIf and the Ternary Operator

IIf (in VB) and the ternary operator (in C#) receive as parameters one conditional expression (which returns True or False), and two values. If the condition is True, the first value is returned, and if the condition is False, the second value is returned.

In our case, the conditional expression verifies whether the Name field is empty, which will be the case if we’re inserting a new row. So, when we’re inserting a new row, we display “Adding New Employee” in the DetailsView’s header; otherwise, we display the name of the employee whose details are being edited.

Now, when we insert a new employee record, DetailsView will display “Adding

New Employee” in its header; when we’re editing or displaying an existing employee’s details, it will display the name of that employee, as Figure 12.14 shows.

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Binding the DetailsView to a SqlDataSource

Figure 12.14. Adding a new employee, and displaying the new header

One minor hitch with this solution is that the GridView isn’t instantly updated when we make a change using the DetailsView control. Try modifying the name of a user; even after you press the Update link in the DetailsView, the GridView will still show the old value. Only after you reload the page will the data be displayed correctly by the GridView.

This issue occurs because the GridView is populated before the DetailsView updates the database. To avoid this problem, we could use a simple workaround that forces the GridView to update itself in response to the occurrence of certain events raised by the DetailsView control. These events are ItemUpdated, ItemDeleted, and ItemInserted. Use Visual Web Developer to generate the event handlers for these events, and update the code like this:

Visual Basic

File: AddressBook.aspx.vb (excerpt)

Protected Sub employeeDetails_ItemUpdated( _

ByVal sender As Object, ByVal e As _

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Chapter 12: Advanced Data Access

System.Web.UI.WebControls.DetailsViewUpdatedEventArgs) _ Handles employeeDetails.ItemUpdated

grid.DataBind()

End Sub

Protected Sub employeeDetails_ItemDeleted( _ ByVal sender As Object, ByVal e As _

System.Web.UI.WebControls.DetailsViewDeletedEventArgs) _ Handles employeeDetails.ItemDeleted

grid.DataBind()

End Sub

Protected Sub employeeDetails_ItemInserted( _ ByVal sender As Object, ByVal e As _

System.Web.UI.WebControls.DetailsViewInsertedEventArgs) _ Handles employeeDetails.ItemInserted

grid.DataBind()
End Sub
C#	File: AddressBook.aspx.cs (excerpt)

protected void employeeDetails_ItemUpdated(object sender, DetailsViewUpdatedEventArgs e)

{

grid.DataBind();

}

protected void employeeDetails_ItemDeleted(object sender, DetailsViewDeletedEventArgs e)

{

grid.DataBind();

}

protected void employeeDetails_ItemInserted(object sender, DetailsViewInsertedEventArgs e)

{

grid.DataBind();

}

Now your GridView and DetailsView controls will be permanently synchronized.

The last improvement we’ll make is to add an Add New Employee button to the page. Right now, we can only add new employees if we select an employee from the GridView, but this isn’t exactly an intuitive way to work! Let’s add a button that will make the DetailsView control display in insert mode when it’s clicked by a user.

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Binding the DetailsView to a SqlDataSource

Figure 12.15. The Add New Employee button

Add the new button above the grid like this:

File: AddressBook.aspx (excerpt)

<h1>Address Book</h1>

<asp:LinkButton id="addEmployeeButton" runat="server" Text="Add New Employee" /><br />

<asp:GridView id="grid" runat="server" …

Double-click the button in Design View, and fill in its Click event handler like this:

Visual Basic

File: AddressBook.aspx.vb (excerpt)

Protected Sub addEmployeeButton_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) Handles addEmployeeButton.Click

employeeDetails.ChangeMode(DetailsViewMode.Insert) End Sub

C#	File: AddressBook.aspx.cs (excerpt)

protected void addEmployeeButton_Click(object sender, EventArgs e)

{

employeeDetails.ChangeMode(DetailsViewMode.Insert);

}

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Our new button (shown in Figure 12.15) will cause the DetailsView to display in insert mode when clicked.

Your Address Book is now fully featured, and ready for production!

What’s really interesting about the code that was generated for us in this section is the definition of the employeeDataSource. Since this data source needs to store the details of selecting, deleting, updating, and inserting rows, it looks significantly bigger than the employeesDataSource:

File: AddressBook.aspx (excerpt)

<asp:SqlDataSource ID="employeeDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:Dorknozzle %>" DeleteCommand="DELETE FROM [Employees]

WHERE [EmployeeID] = @EmployeeID" InsertCommand="INSERT INTO [Employees] ([DepartmentID],

[Name], [Username], [Password], [Address], [City], [State], [Zip], [HomePhone], [Extension], [MobilePhone]) VALUES (@DepartmentID, @Name, @Username, @Password, @Address, @City, @State, @Zip, @HomePhone, @Extension, @MobilePhone)"

SelectCommand="SELECT [EmployeeID], [DepartmentID], [Name], [Username], [Password], [Address], [City], [State], [Zip], [HomePhone], [Extension], [MobilePhone]

FROM [Employees]

WHERE ([EmployeeID] = @EmployeeID)" UpdateCommand="UPDATE [Employees]

SET [DepartmentID] = @DepartmentID, [Name] = @Name, [Username] = @Username, [Password] = @Password, [Address] = @Address, [City] = @City, [State] = @State, [Zip] = @Zip, [HomePhone] = @HomePhone,

[Extension] = @Extension, [MobilePhone] = @MobilePhone WHERE [EmployeeID] = @EmployeeID">

<DeleteParameters>

<asp:Parameter Name="EmployeeID" Type="Int32" /> </DeleteParameters>

<UpdateParameters>

<asp:Parameter Name="DepartmentID" Type="Int32" /> <asp:Parameter Name="Name" Type="String" /> <asp:Parameter Name="Username" Type="String" /> <asp:Parameter Name="Password" Type="String" /> <asp:Parameter Name="Address" Type="String" /> <asp:Parameter Name="City" Type="String" /> <asp:Parameter Name="State" Type="String" /> <asp:Parameter Name="Zip" Type="String" />

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