学习ASP.NET MVC框架揭秘笔记-实例演示：SC模式的应用
实例演示：SC模式的应用
为了对SC模式下的MVP，尤其是该模式下的View和Presenter之间的交互方式有一个深刻的认识，我们现在来做一个实例演示。我们采用员工查询的场景，用ASP.NET Web Forms来建立这个简单的应用。
我们先来定义员工的数据类型，Employee来表示一个员工，有5个属性：ID、姓名、性别、出生日期和部门。
public class Employee
{
public string Id { get; private set; }
public string Name { get; private set; }
public string Gender { get; private set; }
public DateTime BirthDate { get; private set; }
public string Department { get; private set; }
public Employee(string id, string name, string gender,DateTime birthDate, string department)
{
this.Id = id;
this.Name = name;
this.Gender = gender;
this.BirthDate = birthDate;
this.Department = department;
}作为包含应用状态和状态操作行为的Model，通过如下一个简单的EmployeeRepository类型来体现。表示所有员工列表的数据通过一个静态字段来维护，而GetEmployees方法返回指定部门的员工列表。如果没有指定筛选部门或者指定的部门字符为空，该方法直接返回所有员工列表。
public class EmployeeRepository
{
private static IList<Employee> employees;
static EmployeeRepository()
{
employees = new List<Employee>();
employees.Add(new Employee("001", "张三", "男",new DateTime(1981, 8, 24), "销售部"));
employees.Add(new Employee("002", "李四", "女",new DateTime(1982, 7, 10), "人事部"));
employees.Add(new Employee("003", "王五", "男",new DateTime(1981, 9, 21), "人事部"));
}
public IEnumerable<Employee> GetEmployees(string department = "")
{
if (string.IsNullOrEmpty(department))
{
return employees;
}
return employees.Where(e => e.Department == department).ToArray();
}
}接下来我们看看作为View接口的IEmployeeView的定义。该接口定义了BindEmployees和BindDepartments两个方法，分别用于绑定基于部门列表的DropDownList和基于员工列表的GridView。除此之外，IEmployeeView接口还定义了一个事件DepartmentSelected，该事件会在用户选择了筛选部门之后单机查询按钮时触发。DepartmentSelected事件参数类型为自定义的DepartmentSelectedEventAges，属性Department表示用户选择的部门。
public interface IEmployeeView
{
void BindEmployees(IEnumerable<Employee> employees);
void BindDepartments(IEnumerable<string> departments);
event EventHandler<DepartmentSelectedEventArgs> DepartmentSelected;
}
public class DepartmentSelectedEventArgs : EventArgs
{
public string Department { get; private set; }
public DepartmentSelectedEventArgs(string department)
{
this.Department = department;
}
}
作为MVP三角关系核心的Presenter通过EmployeePresenter表示。里面包含两个属性，一个代表View的只读属性IEmployeeView接口 的View，而另一个代表Model的只读属性EmployeeRepository对象的Repository，两个属性均在构造函数中初始化。
public class EmployeePresenter
{
public IEmployeeView View { get; private set; }
public EmployeeRepository Repository { get; private set; }
public EmployeePresenter(IEmployeeView view)
{
this.View = view;
this.Repository = new EmployeeRepository();
this.View.DepartmentSelected += OnDepartmentSelected;
}
public void Initialize()
{
IEnumerable<Employee> employees = this.Repository.GetEmployees();
this.View.BindEmployees(employees);
string[] departments = new string[] { "", "销售部", "采购部", "人事部", "IT部" };
this.View.BindDepartments(departments);
}
protected void OnDepartmentSelected(object sender, DepartmentSelectedEventArgs args)
{
string department = args.Department;
var employees = this.Repository.GetEmployees(department);
this.View.BindEmployees(employees);
}
}
我们在构造函数中注册了View的DepartmentSelected事件，作为事件处理器的OnDepartmentSelected方法通过调用Repository（即Model）得到了用户选择部门下的员工列表，并且绑定到了View上。
下面我们来看看View的Web页面。
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>员工管理</title>
<link rel="stylesheet" href="Content/bootstrap.css" />
<link rel="stylesheet" href="Content/site.css" />
</head>
<body>
<form id="form1" runat="server">
<div id="page">
<div class="text-center">
<asp:DropDownList ID="DropDownListDepartments" runat="server" CssClass="form-inline" />
<asp:Button ID="ButtonSearch" runat="server" Text="查询" OnClick="ButtonSearch_Click" CssClass="btn-primary" />
</div>
<asp:GridView ID="GridViewEmployees" runat="server" AutoGenerateColumns="false" Width="100%" CssClass="table table-bordered">
<Columns>
<asp:BoundField DataField="Name" HeaderText="姓名" />
<asp:BoundField DataField="Gender" HeaderText="性别" />
<asp:BoundField DataField="BirthDate" HeaderText="出生日期" DataFormatString="{0:dd/MM/yyyy}" />
<asp:BoundField DataField="Department" HeaderText="部门"/>
</Columns>
</asp:GridView>
</div>
</form>
</body>
</html>
下面是Web页面的后台代码定义，他实现了定义在IEmployeeView接口的方法和事件。
public partial class Default : System.Web.UI.Page, IEmployeeView
{
public EmployeePresenter Presenter { get; private set; }
public event EventHandler<DepartmentSelectedEventArgs> DepartmentSelected;
public Default()
{
this.Presenter = new EmployeePresenter(this);
}
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
this.Presenter.Initialize();
}
}
protected void ButtonSearch_Click(object sender, EventArgs e)
{
string department = this.DropDownListDepartments.SelectedValue;
DepartmentSelectedEventArgs eventArgs = new DepartmentSelectedEventArgs(department);
if (null != DepartmentSelected)
{
DepartmentSelected(this, eventArgs);
}
}
public void BindEmployees(IEnumerable<Employee> employees)
{
this.GridViewEmployees.DataSource = employees;
this.GridViewEmployees.DataBind();
}
public void BindDepartments(IEnumerable<string> departments)
{
this.DropDownListDepartments.DataSource = departments;
this.DropDownListDepartments.DataBind();
}
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