cis 375—web app dev ii

CIS 375—Web App Dev II

ASP .NET 10Database 2

2

Introduction to Server-Side Data

Server-side data access is unique in that Web pages are basically ___________.

This presents some difficult challenges when trying to perform database transactions.

The __________ control can help manage these challenges, allowing you to concentrate more on your application logic and less on the details of state management and event handling.

3

Connections, Commands, and Datasets 1

The common language _________ provides a complete set of managed data access APIs for data-intensive application development.

These APIs help to abstract the data and present it in a consistent way regardless of its actual source (SQL Server, OLEDB, XML, and so on).

There are essentially three objects you will work with most often:

A __________ represents a physical connection to some data store. A __________ represents a directive to retrieve from (select) or

manipulate (insert, update, delete) the data store. A __________ represents the actual data an application works with.

4

Namespaces To give your page access to the classes you

will need to perform SQL data access, you must import the System.Data and System.Data.SqlClient namespaces into your page. <%@ Import Namespace="System.Data" %>

<%@ Import Namespace="System.Data.SqlClient" %>

5

SQL Query To perform a select query to a SQL database,

you create a SqlConnection to the database passing the connection string, and then construct a SqlDataAdapter object that contains your query statement.

Dim myConnection As New SqlConnection( _ "server=(local)\NetSDK;database=pubs;Integrated Security=SSPI")

Dim myCommand As New SqlDataAdapter("select * from Authors", myConnection)

To populate a DataSet object with the results from the query, you call the command's ______ method.

Dim ds As New DataSet()

myCommand.Fill(ds, "Authors")

6

SqlDataReader For Web applications, you are usually performing short

operations with each request (commonly to simply display the data).

You often don't need to hold a ________ object over a series of several requests. For situations like these, you can use a SqlDataReader.

Dim myCommand As SqlCommand = New SqlCommand("select * from Authors", myConnection)

myConnection.Open()

Dim dr As SqlDataReader = myCommand.ExecuteReader()

...

myConnection.Close()

7

SqlCommand When performing commands that do not

require data to be returned, such as inserts, updates, and deletes, you also use a SqlCommand.

Dim myConnection As New SqlConnection( "server=(local)\NetSDK;database=pubs;Integrated Security=SSPI")

Dim myCommand As New SqlCommand("UPDATE Authors SET phone='(800) 555-5555' WHERE au_id = '123-45-6789'", myConnection)

myCommand.Connection.Open()

myCommand.ExecuteNonQuery()

myCommand.Connection.Close()

8

Binding SQL Data to a DataGrid 1

The following sample shows a simple select query bound to a DataGrid control.

The DataGrid renders a table containing the SQL data.

DataGrid1.aspx [Run Sample] | [View Source] The DefaultView property represents the

current state of a table within a DataSet, including any changes which have been made by application code.

After setting the DataSource property, you call DataBind() to populate the control.

MyDataGrid.DataSource=ds.Tables("Authors").DefaultView

MyDataGrid.DataBind()

9

Binding SQL Data to a DataGrid 2

An alternative syntax is to specify both a DataSource and a DataMember. In this case, ASP.NET automatically gets the DefaultView for you.

MyDataGrid.DataSource=ds

MyDataGrid.DataMember="Authors"

MyDataGrid.DataBind() You can also bind directly to a SqlDataReader. In this case you are only displaying data, so the

forward-only nature of the SqlDataReader is perfectly suited to this scenario, and you benefit from the performance boost that SqlDataReader provides.

DataGrid1.1.aspx [Run Sample] | [View Source]

10

Performing a Parameterized Select 1

You can also perform a parameterized select using the SqlDataAdapter object.

The following sample shows how you can modify the data selected using the value posted from a select HtmlControl.

DataGrid2.aspx [Run Sample] | [View Source]

11


The SqlDataAdapter maintains a Parameters collection that can be used to replace variable identifiers (denoted by an “___" in front of the name) with values.

You add a new SqlParameter to this collection that specifies the name, type, and size of the parameter, and then set its Value property to the value of the select.

myCommand.SelectCommand.Parameters.Add(New SqlParameter("@State", SqlDbType.NVarChar, 2))

myCommand.SelectCommand.Parameters("@State").Value = MySelect.Value

12


DataGrid2.aspx statically populates the values of the select box, but this will not work well if those values ever change in the database.

Because the select HtmlControl also supports an IEnumerable DataSource property, you can use a ________ query to dynamically populate the select box instead, which guarantees that the database and user interface are always in sync.

The following sample demonstrates this process. DataGrid3.aspx [Run Sample] | [View Source]

13

Inserting Data in a Database 1

Add a simple input _______ to the page. Execute an insert command in the form submit

_______ handler. Use the command object's Parameters collection

to populate the command's values. Check to make sure the required values are not

null before attempting to insert into the database.

Execute the insert command inside of a __________ block, just in case the primary key for inserted row already exists.


14

Inserting Data in a Database 2

Instead of explicitly checking the input values, you could have just as easily used the _________ controls provided with ASP.NET.

Note that using the RegEx Validator provides the additional benefit of checking the format for certain kinds of fields.


15

Updating Data in a Database 1 To allow rows to be edited, the DataGrid

supports an integer EditItemIndex property, which indicates which ______ of the grid should be editable.

When this property is set, the DataGrid renders the row at that index as text input boxes instead of simple ________.

The DataGrid can contain an EditCommandColumn that renders ______ for firing three special events: EditCommand, UpdateCommand, and CancelCommand.

16

Updating Data in a Database 2 On the DataGrid tag itself, you wire event

_________ to each of the commands fired from the EditCommandColumn.

The DataGridCommandEventArgs argument of these handlers gives you direct access to the _______ selected by the client, which you use to set the DataGrid's EditItemIndex.

Performing an update query requires that you know the ___________ in the database for the row you wish to update. To support this, the DataGrid exposes a DataKeyField property that you can set to the field name for the primary key.


17

Updating Data in a Database 3 One problem with the preceding example is

that the primary key field (au_id) also renders as a text input box when a row is editable.

You can disable this column from rendering as a text box by specifying exactly what each column looks like for the editable row.

You do this by defining each row in the DataGrid's _________ collection, using the BoundColumn control to assign data fields with each column.


18

Updating Data in a Database 4 You can also specify a TemplateColumn,

which gives you complete control over the contents of the column.

The following sample demonstrates using the TemplateColumn control to render the "State" column as a drop-down list and the "Contract" column as a check box ____________.

DataGrid8.aspx [Run Sample] | [View Source] The following sample adds Validator controls

to the columns to check the ______ input before attempting to perform the update.


19

Deleting Data in a Database

Another control that can be added to the DataGrid's Columns collection is the ButtonColumn control.

ButtonColumn supports a CommandName property that can be set to Delete.

On the DataGrid, you _____ an event handler to the DeleteCommand, where you perform the delete operation.


20

Sorting Data from a Database 1

While the DataGrid control doesn't explicitly sort its data for you, it does provide a way to call an event handler when the user clicks a column header, which you can use to sort the data.

When the DataGrid's AllowSorting property is set to true, it renders __________ for the column headers that fire a Sort command back to the grid.

You set the OnSortCommand property of the DataGrid to the handler you want to call when the user clicks a column link.

21

Sorting Data from a Database 2

The name of the column is passed as a SortExpression property on the DataGridSortCommandEventArgs argument, which you can use to set the Sort property of the DataView bound to the grid.

DataGrid11.aspx [Run Sample] | [View Source] When using BoundColumn controls, you can

explicitly set the SortExpression property for each column, as demonstrated in the following sample.


22

Working with Master-Detail Relationships

A very common Web-based interface is one in which a row of data can be selected that navigates the client to a “________" page.

To accomplish this using the DataGrid, you can add a HyperLinkColumn to the __________ collection, which specifies the details page to which the client will navigate when the link is clicked.

On the details page, you retrieve the ___________ argument and perform a join select to obtain details from the database.


Columns

23

Writing and Using Stored Procedures

Using stored procedures can reduce the cost of performing _______ database operations in an application.

A stored procedure is easy to create, and can even be done using a ______ statement. CREATE Procedure GetAuthors AS

SELECT * FROM Authors return

GO

You indicate to the SqlCommand that the CommandText is a stored procedure by setting the CommandType property.


24

Accessing XML-based Data The DataSet supports a ReadXml method that

takes a FileStream object as its parameter. Each TableName section corresponds to a

single _____ in the table. DataGrid17.aspx [Run Sample] | [View

Source] You can also read the data and _________

separately, using the ReadXmlData and ReadXmlSchema methods of the DataSet.


cis 375—web app dev ii

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