我已经使用ajax级联下拉列表绑定了dropdownlist，并使用了web方法，它可以正常工作，并且我能够将国家和州ID保存在数据库中。现在，我想将已保存的ID绑定到填充方法的dropdownlist上，我该如何实现。
aspx代码位于:::
<li>
<asp:DropDownList ID="ddlCountry" runat="server" TabIndex="11"></asp:DropDownList>
<ajax:CascadingDropDown ID="csdCountry" runat="server" Category="Country" TargetControlID="ddlCountry" PromptText="-- Select Country --" LoadingText=" [Loading Countries...]" ServiceMethod="FetchCountries" ServicePath="~/AjaxCascadingDropDown.asmx"></ajax:CascadingDropDown>
</li>
<li>
<asp:DropDownList ID="ddlState" runat="server" TabIndex="12"></asp:DropDownList>
<ajax:CascadingDropDown ID="csdState" runat="server" ParentControlID="ddlCountry" Category="State" TargetControlID="ddlState" PromptText="-- Select State --" LoadingText="[Loading States...]" ServiceMethod="FetchStates" ServicePath="~/AjaxCascadingDropDown.asmx"></ajax:CascadingDropDown>
</li>
Web方法代码位于:::
[WebMethod]
public CascadingDropDownNameValue[] FetchCountries(string knownCategoryValues, string category)
{
GetLookupResponse countryLookupResponse = commonService.GetLookup("Country");
List<CascadingDropDownNameValue> countries = new List<CascadingDropDownNameValue>();
foreach (var countryData in countryLookupResponse.LookupItems)
{
string CountryID = countryData.ID.ToString();
string CountryName = countryData.Description.ToString();
countries.Add(new CascadingDropDownNameValue(CountryName, CountryID));
}
return countries.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] FetchStates(string knownCategoryValues, string category)
{
int countryId;
StringDictionary strCountries = AjaxControlToolkit.CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
countryId = Convert.ToInt32(strCountries["Country"]);
GetLookupResponse stateLookupResponse = commonService.GetLookup("State");
List<CascadingDropDownNameValue> states = new List<CascadingDropDownNameValue>();
foreach (var StateData in stateLookupResponse.LookupItems.Where(id => id.dependencyID == countryId))
{
string StateID = StateData.ID.ToString();
string StateName = StateData.Description.ToString();
states.Add(new CascadingDropDownNameValue(StateName, StateID));
}
return states.ToArray();
}
填充下拉列表代码:::
ddlCountry.SelectedValue = address.Country.ID.ToString();
ddlState.SelectedValue = address.State.ID.ToString();
ddlCity.SelectedValue = address.City.ID.ToString();
答案 0 :(得分：0)
对每个实体使用3个DropDownLists，映射如下所示
ddlContinents-大陆列表
ddlCountry-国家列表
ddlCity-城市列表
<span style ="font-family:Arial">Select Continent : </span>
<asp:DropDownList ID="ddlContinents" runat="server" AutoPostBack = "true"
OnSelectedIndexChanged="ddlContinents_SelectedIndexChanged">
<asp:ListItem Text = "--Select Continent--" Value = ""></asp:ListItem>
</asp:DropDownList>
<br /><br />
<span style ="font-family:Arial">Select Country : </span>
<asp:DropDownList ID="ddlCountry" runat="server" AutoPostBack = "true"
Enabled = "false" OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged">
<asp:ListItem Text = "--Select Country--" Value = ""></asp:ListItem>
</asp:DropDownList>
<br /><br />
<span style ="font-family:Arial">Select City : </span>
<asp:DropDownList ID="ddlCity" runat="server" AutoPostBack = "true"
Enabled = "false" OnSelectedIndexChanged="ddlCity_SelectedIndexChanged">
<asp:ListItem Text = "--Select City--" Value = ""></asp:ListItem>
</asp:DropDownList>
<br /><br />
<asp:Label ID="lblResults" runat="server" Text="" Font-Names = "Arial" />
将OnSelectedIndexChanged事件添加到所有DropDownLists，还将AutoPostBack设置属性设置为true。
在页面的Page_Load事件中，我正在填充大陆DropDownList
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ddlContinents.AppendDataBoundItems = true;
String strConnString = ConfigurationManager
.ConnectionStrings["conString"].ConnectionString;
String strQuery = "select ID, ContinentName from Continents";
SqlConnection con = new SqlConnection(strConnString);
SqlCommand cmd = new SqlCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = strQuery;
cmd.Connection = con;
try
{
con.Open();
ddlContinents.DataSource = cmd.ExecuteReader();
ddlContinents.DataTextField = "ContinentName";
ddlContinents.DataValueField = "ID";
ddlContinents.DataBind();
}
catch (Exception ex)
{
throw ex;
}
finally
{
con.Close();
con.Dispose();
}
}
}
下一步，在父大陆DropDownList的SelectedIndexChanged事件上，我正在根据用户选择的大陆ID填充国家DropDownList
protected void ddlContinents_SelectedIndexChanged(object sender, EventArgs e)
{
ddlCountry.Items.Clear();
ddlCountry.Items.Add(new ListItem("--Select Country--", ""));
ddlCity.Items.Clear();
ddlCity.Items.Add(new ListItem("--Select City--", ""));
ddlCountry.AppendDataBoundItems = true;
String strConnString = ConfigurationManager
.ConnectionStrings["conString"].ConnectionString;
String strQuery = "select ID, CountryName from Countries " +
"where ContinentID=@ContinentID";
SqlConnection con = new SqlConnection(strConnString);
SqlCommand cmd = new SqlCommand();
cmd.Parameters.AddWithValue("@ContinentID",
ddlContinents.SelectedItem.Value);
cmd.CommandType = CommandType.Text;
cmd.CommandText = strQuery;
cmd.Connection = con;
try
{
con.Open();
ddlCountry.DataSource = cmd.ExecuteReader();
ddlCountry.DataTextField = "CountryName";
ddlCountry.DataValueField = "ID";
ddlCountry.DataBind();
if (ddlCountry.Items.Count > 1)
{
ddlCountry.Enabled = true;
}
else
{
ddlCountry.Enabled = false;
ddlCity.Enabled = false;
}
}
catch (Exception ex)
{
throw ex;
}
finally
{
con.Close();
con.Dispose();
}
}
您会注意到我正在使用DropDownList的SelectedItemValue属性将大洲的ID作为参数传递给查询，因此查询返回该大陆ID的记录（国家），然后将其绑定到Country DropDownList
填充城市DropDownList
现在选择国家（地区）时，我正在将该城市的城市填充到城市下拉列表中。
protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
ddlCity.Items.Clear();
ddlCity.Items.Add(new ListItem("--Select City--", ""));
ddlCity.AppendDataBoundItems = true;
String strConnString = ConfigurationManager
.ConnectionStrings["conString"].ConnectionString;
String strQuery = "select ID, CityName from Cities " +
"where CountryID=@CountryID";
SqlConnection con = new SqlConnection(strConnString);
SqlCommand cmd = new SqlCommand();
cmd.Parameters.AddWithValue("@CountryID",
ddlCountry.SelectedItem.Value);
cmd.CommandType = CommandType.Text;
cmd.CommandText = strQuery;
cmd.Connection = con;
try
{
con.Open();
ddlCity.DataSource = cmd.ExecuteReader();
ddlCity.DataTextField = "CityName";
ddlCity.DataValueField = "ID";
ddlCity.DataBind();
if (ddlCity.Items.Count > 1)
{
ddlCity.Enabled = true;
}
else
{
ddlCity.Enabled = false;
}
}
catch (Exception ex)
{
throw ex;
}
finally
{
con.Close();
con.Dispose();
}
}
上面，我在“城市”表上触发查询，并获取用户选择的属于该国家的所有城市。
显示结果
最后，在City DropDownList的SelectedIndexChanged事件中，我正在显示用户所做的完整选择。
protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
{
lblResults.Text = "You Selected " +
ddlContinents.SelectedItem.Text + " -----> " +
ddlCountry.SelectedItem.Text + " -----> " +
ddlCity.SelectedItem.Text;
}