C# FormView中的依赖DropDownList

我试图在表单视图中创建两个下拉列表，其中第二个下拉列表中显示的值取决于第一个下拉列表。第一个列表包含sql表“Classes”中包含的类号，第二个下拉列表包含同一sql表“Classes”中的类节。我希望能够选择一个类号，并且只弹出与该类号对应的部分

示例类表：

Number:   Section:   SLN:  
210       1          A-1  
210       2          A-2  
210       3          A-3  
340       1          B-1  
340       7          B-7 

我目前有第一个正确设置使用的号码列表

   <asp:DropDownList ID="ddlNumber" runat="server" 
    DataSourceID="SqlDSClasses"
     AutoPostBack="True" DataTextField="Number" DataValueField="Number">
    </asp:DropDownList> 
for the drop down and

<asp:SqlDataSource ID="SqlDSClasses" runat="server"       
ConnectionString="<%$ ConnectionStrings:ReinstatementCS %>" 
SelectCommand="SELECT [Prefix], [Number], [Location], [SLN],                              
[StartTime], [EndTime], [ClassDay], [ClassCredit], [ClassSection] FROM [Classes]">   
</asp:SqlDataSource>
for the corresponding SqlDataSource

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看看这篇文章：

它解释了如何实现你想要的

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另外，您也可以使用AJAX:

看看这篇文章：

它解释了如何实现你想要的

---

另外，您也可以使用AJAX:

我知道了怎么做： 我的C#代码现在看起来像这样：

protected void ddlNumber_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ddlNumber = FVStudentClass.FindControl("ddlNumber") as DropDownList;

    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ReinstatementCS"].ConnectionString);
    SqlCommand myCommand = new SqlCommand("SELECT DISTINCT ClassSection FROM Classes WHERE Number = " + ddlNumber.Text);
    myCommand.Connection = con;
    SqlDataAdapter da = new SqlDataAdapter(myCommand);
    DataTable dt = new DataTable();
    da.Fill(dt);

    DropDownList ddlSection = FVStudentClass.FindControl("ddlSection") as DropDownList;
    ddlSection.DataSource = dt;
    ddlSection.DataTextField = "ClassSection";
    ddlSection.DataValueField = "ClassSection";
    ddlSection.DataBind();
    ddlSection.Items.Insert(0, "--Select--");
}

以及my.aspx下拉列表： 号码：

<asp:DropDownList ID="ddlNumber" runat="server" DataSourceID="SqlDSClasses"  AutoPostBack="True" DataTextField="Number" DataValueField="Number"   onselectedindexchanged="ddlNumber_SelectedIndexChanged">
</asp:DropDownList>

另一页：
（忽略第一个答案中的所有div）
我想出了方法：
我的C#代码现在看起来像这样：

protected void ddlNumber_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ddlNumber = FVStudentClass.FindControl("ddlNumber") as DropDownList;

    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ReinstatementCS"].ConnectionString);
    SqlCommand myCommand = new SqlCommand("SELECT DISTINCT ClassSection FROM Classes WHERE Number = " + ddlNumber.Text);
    myCommand.Connection = con;
    SqlDataAdapter da = new SqlDataAdapter(myCommand);
    DataTable dt = new DataTable();
    da.Fill(dt);

    DropDownList ddlSection = FVStudentClass.FindControl("ddlSection") as DropDownList;
    ddlSection.DataSource = dt;
    ddlSection.DataTextField = "ClassSection";
    ddlSection.DataValueField = "ClassSection";
    ddlSection.DataBind();
    ddlSection.Items.Insert(0, "--Select--");
}

以及my.aspx下拉列表：
号码：

<asp:DropDownList ID="ddlNumber" runat="server" DataSourceID="SqlDSClasses"  AutoPostBack="True" DataTextField="Number" DataValueField="Number"   onselectedindexchanged="ddlNumber_SelectedIndexChanged">
</asp:DropDownList>


另一页：
（忽略第一个答案中的所有div）

protected void ddlNumber_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ddlNumber = FVStudentClass.FindControl("ddlNumber") as DropDownList;

    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ReinstatementCS"].ConnectionString);
    SqlCommand myCommand = new SqlCommand("SELECT DISTINCT ClassSection FROM Classes WHERE Number = " + ddlNumber.Text);
    myCommand.Connection = con;
    SqlDataAdapter da = new SqlDataAdapter(myCommand);
    DataTable dt = new DataTable();
    da.Fill(dt);

    DropDownList ddlSection = FVStudentClass.FindControl("ddlSection") as DropDownList;
    ddlSection.DataSource = dt;
    ddlSection.DataTextField = "ClassSection";
    ddlSection.DataValueField = "ClassSection";
    ddlSection.DataBind();
    ddlSection.Items.Insert(0, "--Select--");
}

<asp:DropDownList ID="ddlNumber" runat="server" DataSourceID="SqlDSClasses"  AutoPostBack="True" DataTextField="Number" DataValueField="Number"   onselectedindexchanged="ddlNumber_SelectedIndexChanged">
</asp:DropDownList>

<asp:DropDownList ID="ddlSection" runat="server"  AutoPostBack="True"                                                     onselectedindexchanged="ddlSection_SelectedIndexChanged">
</asp:DropDownList>