databinding

DatabindingData tastes like chicken, if chicken was data.

DatabindingWhat is it?

Associating a set of data with a control

Why use it?Its much easier than associating data to

controls by hand

We Need Some DataStudent Database

Schema (visio document)The focus here is NOT ON THE DATABASE

If you want to learn the details of how a database works and how to use one, come see our database seminar

Schema

Students

Professors

Courses

How Do We Get the Data?DataAccess.StudentDao studentDao

= new DataAccess.StudentDao();

List<DataObjects.Student> StudentList =

studentDao.SelectAll().ToList();

How Do We Get the Data?

ASPX page<div id="divStudents" runat="server"></div>

Not much, but at least we have a place to put data

Code behind fileprotected void Page_Load(object sender, EventArgs e){ DataAccess.StudentDao studentDao

= new DataAccess.StudentDao(); List<DataObjects.Student> StudentList

= studentDao.SelectAll().ToList();

BindData_TheHardWay(StudentList);}

Code Behind Fileprivate void BindData_TheHardWay(List<DataObjects.Student> StudentList){ foreach (DataObjects.Student student in StudentList) { Label lblId = new Label(); lblId.Text = "Id"; divStudents.Controls.Add(lblId);

TextBox txtId = new TextBox(); txtId.Text = student.StudentId.ToString(); divStudents.Controls.Add(txtId); Label lblFirstName = new Label(); lblFirstName.Text = "First Name"; divStudents.Controls.Add(lblFirstName);

TextBox txtFirstName = new TextBox(); txtFirstName.Text = student.FirstName; divStudents.Controls.Add(txtFirstName);

Label lblLastName = new Label(); lblLastName.Text = "Last Name"; divStudents.Controls.Add(lblLastName);

TextBox txtLastName = new TextBox(); txtLastName.Text = student.LastName; divStudents.Controls.Add(txtLastName); }}

Create Code Behind FileFor every student

For every field you want to show

Create new control for each propertySet the text to the value you want to showAdd that control to the page

Code Behind FileLabel lblId = new Label();lblId.Text = "Id";divStudents.Controls.Add(lblId);

TextBox txtId = new TextBox();txtId.Text = student.StudentId.ToString();divStudents.Controls.Add(txtId);

How’s it look?Eh…

No Line breaksFirst try didn’t go so well

Literal line = new Literal() { Text = "<br />" };

divStudents.Controls.Add(line);

How’s it look?

Data BindingPrevious example gives you complete control

over the controls on the pagePlenty of room for errorTime consuming

Let’s try DataBinding to a Gridview

ASPX File<div id="divStudents" runat="server"> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false"> <Columns> <asp:BoundField DataField="StudentId"

HeaderText="StudentId" /> <asp:BoundField DataField="FirstName"

HeaderText="FirstName" /> <asp:BoundField DataField="LastName"

HeaderText="LastName" /> </Columns> </asp:GridView></div>

Code Behind Fileprotected void Page_Load(object sender, EventArgs e){ DataAccess.StudentDao studentDao

= new DataAccess.StudentDao(); List<DataObjects.Student> StudentList

= studentDao.SelectAll().ToList();

Databind_TheEasyWay(StudentList);}

private void Databind_TheEasyWay(List<DataObjects.Student> StudentList){ GridView1.DataSource = StudentList; GridView1.DataBind();}

How’s it Look?

EvalEval is used to bind to an UI item that is

setup to be read-only It is used for late-bound data (not known

from start)

EvalIn the Code Behind:public string PageData { get; set; }

protected void Page_Load(object sender, EventArgs e){ PageData = "this is a test"; Label1.DataBind();}

EvalThe page has a public property that we fill

with dataLabels aren’t automatically databound

elements, so we have to call DataBind()Controls like DataList, GridView, Repeater call

this method automatically

EvalIn the ASPX file:<asp:Label ID="Label1" runat="server" Text='<%# DataBinder.Eval(Page,"PageData") %>'> </asp:Label>

Eval(From MSDN): Because this method performs

late-bound evaluation, using reflection at run time, it can cause performance noticeably slow compared to standard ASP.NET data-binding syntax.