主要内容
1．CascadingDropDown控件介绍
2．从数据库读取数据并填充CascadingDropDown
一．CascadingDropDown控件介绍
CascadingDropDown通常叫作级联下拉菜单，本文将通过读取Northwind数据库中的Emplyee、Order、OrderDatail信息作为示例，来展示一下它的使用。示例代码如下：
<atlasToolkit:CascadingDropDown ID="CDD1" runat="server">
<atlasToolkit:CascadingDropDownProperties
TargetControlID="DropDownList2"
Category="Model"
PromptText="Please select a model"
LoadingText="[Loading models]"
ServicePath="CarsService.asmx"
ServiceMethod="GetDropDownContents"
ParentControlID="DropDownList1"
SelectedValue="SomeValue">
</atlasToolkit:CascadingDropDownProperties>
</atlasToolkit:CascadingDropDown>
对于CascadingDropDown需要为它添加CascadingDropDownProperties，有多少个下拉列表，就添加几个CascadingDropDownProperties，主要属性如下：
| 属性 | 说明 |
| TargetControlID | 指定要扩展的DropDownList的ID |
| Category | DropDownList表示的类别名称，在WebMethod中会用到 |
| PromptText | 没有选择时显示的文字 |
| LoadingText | 加载数据时显示的文字 |
| ServicePath | 获取数据的Web Service，为每个DropDownList都要指定 |
| ServiceMethod | 获取数据的Web Method |
| ParentControlID | 要扩展的DropDownList的父控件ID |
| SelectedValue | 默认的选择项的值 |
二．从数据库读取数据并填充CascadingDropDown
下面用读取Northwind数据库中的Emplyee、Order、OrderDatail信息，看一个完整的示例。在新建一个Web Site后，先在页面的头部加上：
<%@ Register Assembly="AtlasControlToolkit"加入三个DropDownList，分别用来显示Emplyee，Order，OrderDatail：
Namespace="AtlasControlToolkit"
TagPrefix="atlasToolkit" %>
<div>
<h3>
Employee:
<asp:DropDownList ID="ddlEmployees" runat="server" /><br /><br />
Order:
<asp:DropDownList ID="ddlOrders" runat="server" /><br /><br />
Detail:
<asp:DropDownList ID="ddlOrderDetails" runat="server" />
</h3>
</div>
下面我们添加一个Northwind.asmx的Web Service，编写相关的Web Method：
[WebMethod]
public CascadingDropDownNameValue[] GetEmployees(
string knownCategoryValues, string category)
{
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection connection = new
SqlConnection(connectionString);
SqlCommand command = new SqlCommand("SELECT * FROM Employees");
command.Connection = connection;
connection.Open();
SqlDataAdapter adapter = new SqlDataAdapter(command);
DataSet dataSet = new DataSet();
adapter.Fill(dataSet);
command.Connection.Close();
DataTable tbl = dataSet.Tables[0];
List<CascadingDropDownNameValue> values =
new List<CascadingDropDownNameValue>();
foreach (DataRow dr in tbl.Rows)
{
string sEmployee = (string)dr["FirstName"] + " " +
dr["LastName"];
int iEmployee = (int)dr["EmployeeID"];
values.Add(new CascadingDropDownNameValue(
sEmployee, iEmployee.ToString()));
}
return values.ToArray();
}
注意Web Method的参数签名是不可以改变的，并且它最后返回的是名-值对这种形式的数组。
整个完整后的Web Service如下：
完整代码
using System;
using System.Web;
using System.Collections;
using System.Configuration;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Web.Services;
using System.Web.Services.Protocols;
using AtlasControlToolkit;
using System.Data;
using System.Data.SqlClient;
/**//// <summary>
/// Summary description for Northwind
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class Northwind : System.Web.Services.WebService {
public Northwind () {
//Uncomment the following line if using designed components
//InitializeComponent();
}
[WebMethod]
public CascadingDropDownNameValue[] GetEmployees(
string knownCategoryValues, string category)
{
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection connection = new
SqlConnection(connectionString);
SqlCommand command = new SqlCommand("SELECT * FROM Employees");
command.Connection = connection;
connection.Open();
SqlDataAdapter adapter = new SqlDataAdapter(command);
DataSet dataSet = new DataSet();
adapter.Fill(dataSet);
command.Connection.Close();
DataTable tbl = dataSet.Tables[0];
List<CascadingDropDownNameValue> values =
new List<CascadingDropDownNameValue>();
foreach (DataRow dr in tbl.Rows)
{
string sEmployee = (string)dr["FirstName"] + " " +
dr["LastName"];
int iEmployee = (int)dr["EmployeeID"];
values.Add(new CascadingDropDownNameValue(
sEmployee, iEmployee.ToString()));
}
return values.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] GetOrdersByEmployee(
string knownCategoryValues,
string category)
{
StringDictionary kv = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
int iEmployee;
if (!kv.ContainsKey("Employee") || !Int32.TryParse(kv["Employee"], out iEmployee))
{
return null;
}
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection connection = new
SqlConnection(connectionString);
SqlCommand command =
new SqlCommand("SELECT OrderID FROM Orders WHERE EmployeeID = " + iEmployee);
command.Connection = connection;
connection.Open();
SqlDataAdapter adapter = new SqlDataAdapter(command);
DataSet dataSet = new DataSet();
adapter.Fill(dataSet);
command.Connection.Close();
DataTable tbl = dataSet.Tables[0];
List<CascadingDropDownNameValue> values = new List<CascadingDropDownNameValue>();
foreach (DataRow dr in tbl.Rows)
{
string sOrder = dr["OrderID"].ToString();
int iOrder = (int)dr["OrderID"];
values.Add(new CascadingDropDownNameValue(
sOrder, iOrder.ToString()));
}
return values.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] GetDetailsByOrder(
string knownCategoryValues,
string category)
{
StringDictionary kv = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
int iOrder;
if (!kv.ContainsKey("Order") || !Int32.TryParse(kv["Order"], out iOrder))
{
return null;
}
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection connection = new
SqlConnection(connectionString);
SqlCommand command =
new SqlCommand("SELECT UnitPrice,OrderID FROM [Order Details] WHERE OrderID = " + iOrder);
command.Connection = connection;
connection.Open();
SqlDataAdapter adapter = new SqlDataAdapter(command);
DataSet dataSet = new DataSet();
adapter.Fill(dataSet);
command.Connection.Close();
DataTable tbl = dataSet.Tables[0];
List<CascadingDropDownNameValue> values = new List<CascadingDropDownNameValue>();
foreach (DataRow dr in tbl.Rows)
{
string UnitPrice = dr["UnitPrice"].ToString();
int intOrder = (int)dr["OrderID"];
values.Add(new CascadingDropDownNameValue(
UnitPrice, intOrder.ToString()));
}
return values.ToArray();
}
}
在Web.config中设置连接信息：
<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=RJ-097;User ID=sa;Password=sa;Initial Catalog=Northwind" providerName="System.Data.SqlClient"/>
</connectionStrings>
这时我们再添加CascadingDropDown控件，设置它的属性如下：
<atlasToolkit:CascadingDropDown ID="CascadingDropDown1" runat="server">
<atlasToolkit:CascadingDropDownProperties Category="Employee" ParentControlID=""
PromptText="Select Employee" SelectedValue="" ServiceMethod="GetEmployees" ServicePath="Northwind.asmx"
TargetControlID="ddlEmployees" />
<atlasToolkit:CascadingDropDownProperties Category="Order" ParentControlID="ddlEmployees"
PromptText="Select Order" SelectedValue="" ServiceMethod="GetOrdersByEmployee"
ServicePath="Northwind.asmx" TargetControlID="ddlOrders" />
<atlasToolkit:CascadingDropDownProperties Category="OrderDetail" ParentControlID="ddlOrders"
PromptText="Select OrderDetail" SelectedValue="" ServiceMethod="GetDetailsByOrder"
ServicePath="Northwind.asmx" TargetControlID="ddlOrderDetails" />
</atlasToolkit:CascadingDropDown>
至此，大功告成。运行后效果如下：
选择：
本文作者: