省市联动下拉菜单的实现
一、数据库的建立
为了更好的实现与数据库连接，省表中需要有两个元素，一个是省编号，一个是省名称；市表中需要有三个元素，一个是市编号，一个是市名称，更重要的是这个市改隶属于那个省。
省表（UserProvince）
ProID ProName
1 河南
2 安徽
市表（UserCity）
CityID ProID CityName
1 1 郑州
2 2 合肥
二、代码
后台：（定义两个关于省市的的函数，通过SelectedIndexChanged事件实现对市的筛选）
protected void Page_Load(object sender, EventArgs e)
{
BindProvince();
BindCity();
}
private void BindProvince()
{
string sql = "select ProID,ProName from UserProvince";
SqlConnection conn = new SqlConnection("SqlDataSource1");
SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
DataSet ds = new DataSet();
conn.Open();
adapter.Fill(ds);
conn.Close();
ddlprovince.DataSource = ds.Tables[0];
ddlprovince.DataValueField = "ProID";
ddlprovince.DataTextField = "ProName";
ddlprovince.DataBind();
}
private void BindCity()
{
string sql = "select CityID,ProID,CityName from UserCity; ";
SqlConnection conn = new SqlConnection("SqlDataSource2");
SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
DataSet ds = new DataSet();
conn.Open();
adapter.Fill(ds);
conn.Close();
ddlCity.DataSource = ds.Tables[0];
ddlCity.DataValueField = "CityID";
ddlCity.DataTextField = "CityName";
ddlCity.DataBind();
}
protected void ddlprovince_SelectedIndexChanged(object sender, EventArgs e)
{
int ProID = this.ddlprovince.SelectedIndex + 1;
SqlConnection conn = new SqlConnection();
conn.ConnectionString = "User ID=sa;Initial Catalog=News;Data Source= (local);Password=123";
conn.Open();
SqlCommand cmd = new SqlCommand("select * from [News].[dbo].[UserCity] where ProID=‘"+ProID+"‘");
cmd.Connection = conn;
SqlDataReader sdr = cmd.ExecuteReader();
//绑定
this.ddlCity.DataSource = sdr;
this.ddlCity.DataTextField = "CityName";
this.ddlCity.DataValueField = "CityID";
this.ddlCity.DataBind();
sdr.Close();
conn.Close();
}
}
前台：（两个连接数据库的DropDownList控件）
<asp:DropDownList ID="ddlprovince" runat="server" widtn="55px" DataSourceID="SqlDataSource1" DataTextField="proName" DataValueField="proID" AutoPostBack="True" OnSelectedIndexChanged="ddlprovince_SelectedIndexChanged">
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NewsConnectionString2 %>" SelectCommand="SELECT [proID], [proName] FROM [Userprovince]"></asp:SqlDataSource>
<asp:DropDownList ID="ddlCity" runat="server" widtn="55px" DataTextField="cityName" DataValueField="cityID" AutoPostBack="True">
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:NewsConnectionString3 %>" SelectCommand="SELECT [cityID], [proID], [cityName] FROM [UserCity]"></asp:SqlDataSource>