Beginning ASP.NET 2.0 E-Commerce in C# 2005 From Novice to Professional PHẦN 5 doc

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CHAPTER 8 ■ CATALOG ADMINISTRATION 259 // Enter row into edit mode protected void grid_RowEditing(object sender, GridViewEditEventArgs e) { // Set the row for which to enable edit mode grid.EditIndex = e.NewEditIndex; // Set status message statusLabel.Text = "Editing row # " + e.NewEditIndex.ToString(); // Reload the grid BindGrid(); } 22. While in edit mode, instead of the Edit button, the GridView places two buttons: Update and Cancel. To make editing functional, you need to supply code that reacts when these buttons are clicked. Let’s start with the code that deals with the Cancel button. Follow the same procedure to generate grid_RowCancelingEdit and complete its code like this: // Cancel edit mode protected void grid_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e) { // Cancel edit mode grid.EditIndex = -1; // Set status message statusLabel.Text = "Editing canceled"; // Reload the grid BindGrid(); } Now you have functional Edit and Cancel buttons. When the Edit button is clicked, the grid enters into edit mode, as shown in Figure 8-21. Figure 8-21. Editing department information ■Note The problem with automatically generated editing controls is that they aren’t configurable, unless transformed to template columns. You’ll do this later in a separate exercise for the department description column, where the edit text box needs to be larger than the default size. 23. When the Update button is clicked, a RowUpdating event is raised. Generate its event handler like you did for the other two. Now add the following code for these two events: Darie-Watson_4681C08.fm Page 259 Monday, September 19, 2005 9:55 AM 260 CHAPTER 8 ■ CATALOG ADMINISTRATION // Update row protected void grid_RowUpdating(object sender, GridViewUpdateEventArgs e) { // Retrieve updated data string id = grid.DataKeys[e.RowIndex].Value.ToString(); string name = ((TextBox)grid.Rows[e.RowIndex].Cells[0].Controls[0]).Text; string description = ((TextBox)grid.Rows[e.RowIndex]. Cells[1].Controls[0]).Text; // Execute the update command bool success = CatalogAccess.UpdateDepartment(id, name, description); // Cancel edit mode grid.EditIndex = -1; // Display status message statusLabel.Text = success ? "Update successful" : "Update failed"; // Reload the grid BindGrid(); } 24. Finally, here’s the code for the DeleteCommand event handler. Let Visual Web Developer generate its signature for you, and then add the following code: // Delete a record protected void grid_RowDeleting(object sender, GridViewDeleteEventArgs e) { // Get the ID of the record to be deleted string id = grid.DataKeys[e.RowIndex].Value.ToString(); // Execute the delete command bool success = CatalogAccess.DeleteDepartment(id); // Cancel edit mode grid.EditIndex = -1; // Display status message statusLabel.Text = success ? "Delete successful" : "Delete failed"; // Reload the grid BindGrid(); } 25. The last bit of code to write in this exercise consists of adding the addDepartmentButton_Click event handler method. Generate its signature by double-clicking the Add button in the Design View window and complete the code like this: // Create a new department protected void createDepartment_Click(object sender, EventArgs e) { // Execute the insert command bool success = CatalogAccess.AddDepartment(newName.Text, Darie-Watson_4681C08.fm Page 260 Monday, September 19, 2005 9:55 AM CHAPTER 8 ■ CATALOG ADMINISTRATION 261 newDescription.Text); // Display status message statusLabel.Text = success ? "Insert successful" : "Insert failed"; // Reload the grid BindGrid(); } ■Tip The presentation tier should do input validation when possible—for example, you can check whether the department name and description are valid before trying to add them to the database. Later in this chapter, you’ll learn how to implement validation using the .NET validator controls. How It Works: DepartmentsAdmin.ascx Be sure to test that the new features are functional. Try to add a new department, rename it, and then delete it. This is the first exercise in which you worked with a GridView control, and it’s important to understand how this complex control works. The GridView control is smart enough to be aware of the columns it reads from the data source and display them to the user. Moreover, as you saw when writing the code, you just tell the grid what row you want to enter edit mode, and it automatically transforms the labels into text boxes. The GridView control supports a number of built-in column types: BoundField, CheckBoxField, HyperLinkField, ButtonField, CommandField, ImageField, and TemplateField. The last one, TemplateField, really lets you write your own HTML code for that column, whereas the others have predefined behavior. In this example, you met some of these column types, but you’ll get to work with all of them by the end of this chapter! BoundField is the most usual field type, simply reading the value from the database and displaying it in the grid. Each column type has a number of options you can set that affect its behavior. The most common options are shown in the Add New Column dialog box that you used to add your fields, but you can access more of their properties by clicking GridView’s Smart Link and choosing the Edit Columns entry. To change the default look of the GridView, you have three main options: You can use the Auto Format feature of the grid (accessible by clicking the Smart Link), you can transform the columns into template columns and edit their format manually, or you can use skins. For this case, we chose to create a default skin for the GridView, because it offers the maximum efficiency with the least effort. Default skins apply to all controls of that kind in a web site, so your work will also be much easier when creating other grids later in this book. If you want to have more skins for a certain type of control, you need to create named skins by adding a SkinID property to their definition. However, here we preferred to build a default skin to format all the grids in BalloonShop in an identical way. The simplest way to create a skin is to create a control instance using the designer, rip the unnecessary details, and copy what remains to the .skin file. For BalloonShop, we used styles from the CSS file in the skin, in an effort to keep all the site’s colors in one place. Your new C# code deals with the GridView control. For example, to enter a row into edit mode, you just need to set the GridView’s EditItemIndex property to the index of the column you want to change in the EditCommand event handler method: Darie-Watson_4681C08.fm Page 261 Monday, September 19, 2005 9:55 AM 262 CHAPTER 8 ■ CATALOG ADMINISTRATION // Enter row into edit mode protected void grid_RowEditing(object sender, GridViewEditEventArgs e) { // Set the row for which to enable edit mode grid.EditIndex = e.NewEditIndex; // Set status message statusLabel.Text = "Editing row # " + e.NewEditIndex.ToString(); // Reload the grid BindGrid(); } The RowEditing event handler receives a GridViewEditEventArgs object named e, which contains, among other details, the index of the row on which the Edit button was clicked (e.NewItemIndex). You use this value to inform the GridView to enter in edit mode for that row. You take similar action in the CancelCommand event handler, where you cancel edit mode by setting GridView’s EditIndex to -1. The way these two event handlers work is fairly standard. The methods that modify data (the event handlers for the Update and Delete buttons) need to read information from the data grid and the ID of the item on which the action happens. Because delete and update operations are based on departments’ IDs, you need to obtain somehow the ID of the department to be updated or deleted. The problem is that you can’t extract DepartmentID from the visible part of the GridView, because we chose not to display it for the user (it’s a low-level detail, useless for the user). So, how do you know the ID associated with a GridView row? Fortunately, the designers of the GridView control anticipated this problem and added a DataKeyNames property to the GridView, which can hold one or more keys for each row in the grid. When creating the grid, you set its DataKeyNames property to DepartmentID, causing the grid to retain the ID of each loaded department. The code in grid_RowUpdating demonstrates how to get the ID of the row that is about to updated: // Update row protected void grid_RowUpdating(object sender, GridViewUpdateEventArgs e) { // Retrieve updated data string id = grid.DataKeys[e.RowIndex].Value.ToString(); The rest of the code shows how to retrieve data from the rows of the GridView. Each row in the grid is a collection of cells, and each cell is a collection of controls. Given that you know which control you are looking for, it becomes a fairly easy job to get the name or description of a department. You read the first cell of the row to obtain the name and the second cell to obtain the description. In both cases, you read the first control, which you convert to a TextBox to be able to read the Text property. // Retrieve updated data string id = grid.DataKeys[e.RowIndex].Value.ToString(); string name = ((TextBox)grid.Rows[e.RowIndex].Cells[0].Controls[0]).Text; string description = ((TextBox)grid.Rows[e.RowIndex].Cells[1]. Controls[0]).Text; To make this functionality even clearer, take a look at the following code block, which reads the department’s name from the grid, but in a step-by-step fashion: Darie-Watson_4681C08.fm Page 262 Monday, September 19, 2005 9:55 AM CHAPTER 8 ■ CATALOG ADMINISTRATION 263 protected void grid_RowUpdating(object sender, GridViewUpdateEventArgs e) { // Get the index of the row to be modified int rowIndex = e.RowIndex; // Get a reference to the row being updated GridViewRow gridViewRow = grid.Rows[rowIndex]; // Get the first cell (one which contains the name) TableCell tableCell = gridViewRow.Cells[0]; // Get the first control in the cell Control control = tableCell.Controls[0]; // Access the control through a TextBox reference TextBox textBox = (TextBox)control; // Get the text from the TextBox string name = textBox.Text; After the ID, new name, and new description of the department are known, the business tier is called to apply the changes. The CatalogAccess.UpdateDepartment method returns a Boolean value specifying whether the update was performed successfully, and then the status label is populated based on this value: // Execute the update command bool success = CatalogAccess.UpdateDepartment(id, name, description); // Cancel edit mode grid.EditIndex = -1; // Display status message statusLabel.Text = success ? "Update successful" : "Update failed"; // Reload the grid BindGrid(); } Customizing the GridView with Template Columns In spite of the length of the exercise that you’ve just completed, you must admit that it was so easy to implement the editable GridView! You added columns to the GridView using Visual Web Developer’s interface and set its layout and colors using a skin. Right now, the code of your grid in DepartmentsAdmin.ascx looks like this: <asp:GridView ID="grid" runat="server" DataKeyNames="DepartmentID" Width="100%" OnRowCancelingEdit="grid_RowCancelingEdit" OnRowDeleting="grid_RowDeleting" OnRowEditing="grid_RowEditing" OnRowUpdating="grid_RowUpdating" AutoGenerateColumns="False"> <Columns> <asp:BoundField DataField="Name" HeaderText="Department Name" SortExpression="Name" /> <asp:BoundField DataField="Description" HeaderText="Department Description" SortExpression="Description" /> <asp:HyperLinkField DataNavigateUrlFields="DepartmentID" Darie-Watson_4681C08.fm Page 263 Monday, September 19, 2005 9:55 AM 264 CHAPTER 8 ■ CATALOG ADMINISTRATION DataNavigateUrlFormatString=" /CatalogAdmin.aspx?DepartmentID={0}" Text="View Categories" /> <asp:CommandField ShowEditButton="True" /> <asp:ButtonField CommandName="Delete" Text="Delete" /> </Columns> </asp:GridView> The interesting aspect is that you can’t see any Label or TextBox controls, even though GridView generates them when showing its data and when entering edit mode. The BoundField, HyperLinkField, CommandField, and ButtonField columns take care of rendering themselves without your intervention. The problem with these automated controls is that you don’t have much flexibility with how they show their data. Although you can use a number of techniques to format your GridView’s styles, colors, or fonts (such as by using a skin), the only way to have complete access to the HTML code your grid generates for a certain column is to transform that column to a template column, instead of using predefined column types such as BoundField, HyperLinkField, and so on. When using template columns, you need to manually supply the code for its templates. You’ll do that in the following exercise, where you’ll enlarge the description editing TextBox control. ■Note When transforming an existing field to a template field, its different display templates (such as the editing template—EditItemTemplate or the normal display template—ItemTemplate) are automatically generated for you so you won’t lose any functionality. Exercise: Implementing a Template Column 1. Open DepartmentsAdmin.ascx in Design View, click GridView’s Smart Link and choose Edit Columns. Select the Department Description field and click Convert this field into a TemplateField. 2. You’ll notice the panel on the right becomes empty, because now the GridView no longer takes care of your column’s properties. Click OK. 3. Switch to Source View to see the generated code. The changes aren’t so drastic, but now instead of a single line defining a BoundField entry, you can find a TemplateField entry containing the complete code for the EditItemTeamplate and ItemTemplate templates. (Note that Visual Web Developer smartly generated bound TextBox and Label controls in the two templates, so if you now execute your project, you won’t lose any functionality.) <asp:TemplateField HeaderText="Department Description" SortExpression="Description"> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("Description") %>'> </asp:Label> </ItemTemplate> Darie-Watson_4681C08.fm Page 264 Monday, September 19, 2005 9:55 AM CHAPTER 8 ■ CATALOG ADMINISTRATION 265 <EditItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("Description") %>'> </asp:TextBox> </EditItemTemplate> </asp:TemplateField> 4. While in Source View, change the name of the editing TextBox. Because you’ll need its name to access its value from the code (when updating the departments’ details), it’s important to have a good name for it. Change the control’s name from TextBox1 to descriptionTextBox: <asp:TextBox ID="descriptionTextBox" runat="server" Text='<%# Bind("Description") %>'></asp:TextBox> 5. After converting the description column to a TemplateField, you can edit its templates both in Source View and in Design View. Switch to Design View, click GridView’s Smart Link, and choose Edit Templates. Now, again using the Smart Link, you can choose which template to edit (see Figure 8-22). Figure 8-22. Choosing a template to edit 6. To modify the text box that appears when editing a department, choose EditItemTemplate from the list. Then, select the TextBox control and modify it to suit your preferences by using the Properties window (see Figure 8-23). For this exercise, set its TextMode property to MultiLine, Width to 350px, and Height to 70px: Figure 8-23. Modifying the description editing text box 7. The last step is to change the code-behind file for updating department data. Locate this line in the grid_RowUpdating method in DepartmentsAdmin.ascx.cs: string description = ((TextBox)grid.Rows[e.RowIndex]. Cells[1].Controls[0]).Text; Darie-Watson_4681C08.fm Page 265 Monday, September 19, 2005 9:55 AM 8213592a117456a340854d18cee57603 266 CHAPTER 8 ■ CATALOG ADMINISTRATION 8. Change this line to string description = ((TextBox)grid.Rows[e.RowIndex]. FindControl("descriptionTextBox")).Text; How It Works: Using Template Columns in the GridView Control Execute the project and test the updated functionality to make sure that it still works. Template columns are useful because they give you full control over how the column looks and behaves. In this exercise, you modified the TextBox control used for editing the department description, but now you can use the same technique to change any field in the table. Because you can also change the names of the controls inside your template, you can now access them by name, instead of by location: string description = ((TextBox)grid.Rows[e.RowIndex]. FindControl("descriptionTextBox")).Text; This piece of code demonstrates how to obtain a reference of the TextBox control named descriptionTextBox, convert its Control reference to a TextBox reference, and extract its contents from there. You’ll see some other examples of template columns later in this chapter when you’ll use CheckBox controls instead of Labels and TextBoxes for displaying the value of True/False fields. Administering Categories The category administration bits are similar to what you did for departments, so we won’t need to explain much this time. The main player in the whole categories administration part is the CategoriesAdmin.ascx Web User Control, but first you need to write the data tier and business tier code that will support its functionality. Stored Procedures for Categories Administration The three stored procedures that you need to add to your BalloonShop database are • CreateCategory • UpdateCategory • DeleteCategory The fourth stored procedure that you’ll use, GetCategories, already exists in the database. Add these stored procedures covered in the following sections to the BalloonShop database. CreateCategory CreateCategory adds a new category to the database. Apart from the name and description of the new category, you also need a DepartmentID, which specifies the department the category belongs to. Note that you don’t need to (in fact, you can’t) specify a CategoryID because Darie-Watson_4681C08.fm Page 266 Monday, September 19, 2005 9:55 AM CHAPTER 8 ■ CATALOG ADMINISTRATION 267 CategoryID is an IDENTITY column in the Category table, and its value is automatically gener- ated by the database when inserting a new record. CREATE PROCEDURE CreateCategory (@DepartmentID int, @CategoryName varchar(50), @CategoryDescription varchar(50)) AS INSERT INTO Category (DepartmentID, Name, Description) VALUES (@DepartmentID, @CategoryName, @CategoryDescription) UpdateCategory The UpdateCategory stored procedure updates the name and description of a category. CREATE PROCEDURE UpdateCategory (@CategoryID int, @CategoryName varchar(50), @CategoryDescription varchar(1000)) AS UPDATE Category SET Name = @CategoryName, Description = @CategoryDescription WHERE CategoryID = @CategoryID DeleteCategory DeleteCategory deletes a certain category from the database. If the category has products that belong to it, the database raises an error because the deletion affects the database integrity— remember that you have implemented the One-to-Many relationship between Category and Product tables using a foreign-key relationship back in Chapter 4. In this case, the error is trapped in the business tier, which returns an error code to the presentation tier, which informs the user that an error has occurred. CREATE PROCEDURE DeleteCategory (@CategoryID int) AS DELETE FROM Category WHERE CategoryID = @CategoryID Middle-Tier Methods for Categories Administration Now you’ll write the methods of the CatalogAccess class that support the functionality required by the CategoriesAdmin user control. These methods use the stored procedures mentioned earlier to perform their functionality: GetCategories, CreateCategory, UpdateCategory, and DeleteCategory. Add these methods to your CatalogAccess class in CatalogAccess.cs: Darie-Watson_4681C08.fm Page 267 Monday, September 19, 2005 9:55 AM 268 CHAPTER 8 ■ CATALOG ADMINISTRATION // Create a new Category public static bool CreateCategory(string departmentId, string name, string description) { // get a configured DbCommand object DbCommand comm = GenericDataAccess.CreateCommand(); // set the stored procedure name comm.CommandText = "CreateCategory"; // create a new parameter DbParameter param = comm.CreateParameter(); param.ParameterName = "@DepartmentID"; param.Value = departmentId; param.DbType = DbType.Int32; comm.Parameters.Add(param); // create a new parameter param = comm.CreateParameter(); param.ParameterName = "@CategoryName"; param.Value = name; param.DbType = DbType.String; param.Size = 50; comm.Parameters.Add(param); // create a new parameter param = comm.CreateParameter(); param.ParameterName = "@CategoryDescription"; param.Value = description; param.DbType = DbType.String; param.Size = 1000; comm.Parameters.Add(param); // result will represent the number of changed rows int result = -1; try { // execute the stored procedure result = GenericDataAccess.ExecuteNonQuery(comm); } catch { // any errors are logged in GenericDataAccess, we ignore them here } // result will be 1 in case of success return (result != -1); } Darie-Watson_4681C08.fm Page 268 Monday, September 19, 2005 9:55 AM [...]... to the code for administering departments, sometimes you need to read the DepartmentID parameter from the query string, which represents the ID of the department for which you’re editing the categories You also have a LinkButton control that generates the link for going back to the main page To implement its functionality, you composed the link to the main catalog admin page by reading the value of Request.ApplicationPath... HyperLinkField This is because a more complex link had to be created, which needed to include both the CategoryID (from the data source) and the DepartmentID (from the query string) Darie-Watson_4681C08.fm Page 277 Monday, September 19, 20 05 9 :55 AM CHAPTER 8 ■ CATALOG ADMINISTRATION . ((TextBox)grid.Rows[e.RowIndex]. Cells[1].Controls [0] ).Text; Darie-Watson_4681C08.fm Page 26 5 Monday, September 19, 20 05 9 :55 AM 821 359 2a117 456 a3 408 54 d18cee57 603 26 6 CHAPTER 8 ■ CATALOG ADMINISTRATION 8. Change this line to string description. properties to their defaults). . Darie-Watson_4681C08.fm Page 27 2 Monday, September 19, 20 05 9 :55 AM 821 359 2a117 456 a3 408 54 d18cee57 603 CHAPTER 8 ■ CATALOG ADMINISTRATION 27 3 7. The template field from. Displaying categories for department AdminPageText LinkButton goBackLink (go back to departments) AdminPageText GridView grid Darie-Watson_4681C08.fm Page 27 1 Monday, September 19, 20 05 9 :55 AM 27 2 CHAPTER
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