[英]How to use the DropDownList's SelectedIndexChanged event
我的網絡表單中有兩個DropDownList
,當我在第一個下拉列表中選擇一個值時,我希望在第二個下拉列表中自動選擇一個相關值。
這是我目前擁有的:
<table>
<tr>
<td>
<asp:Label ID="lbmanu" runat="server" Text="Furniture Manufacturer :
"></asp:Label>
</td>
<td>
<asp:DropDownList ID="ddmanu" runat="server"
DataSourceID="Sql_fur_model_manu"
DataTextField="manufacturer" DataValueField="manufacturer"
onselectedindexchanged="ddmanu_SelectedIndexChanged">
</asp:DropDownList>
<asp:SqlDataSource ID="Sql_fur_model_manu" runat="server"
ConnectionString="<%$ ConnectionStrings:conStr %>"
SelectCommand="SELECT DISTINCT [manufacturer] FROM
[furniture_manufacturer]">
</asp:SqlDataSource>
</td>
</tr>
<tr>
<td>
<asp:Label ID="lbtype" runat="server" Text="Furniture Type :
"></asp:Label>
</td>
<td>
<asp:DropDownList ID="ddtype" runat="server" AutoPostBack="True">
</asp:DropDownList>
</td>
</tr>
</table>
背后的代碼:
protected void ddmanu_SelectedIndexChanged(object sender, EventArgs e)
{
string query = "select furniture from furniture_model where manufacturer='" +
ddmanu.SelectedValue.ToString() + "'";
con.Open();
cmd = new SqlCommand(query, con);
DataTable dt = Select(query);
cmd.ExecuteNonQuery();
ddtype.DataSource = dt;
ddtype.DataTextField = "manufacturer";
ddtype.DataValueField = "furniture";
ddtype.DataBind();
}
您應該將AutoPostBack =“ true”添加到DropDownList1
<asp:DropDownList ID="ddmanu" runat="server" AutoPostBack="true"
DataSourceID="Sql_fur_model_manu"
DataTextField="manufacturer" DataValueField="manufacturer"
onselectedindexchanged="ddmanu_SelectedIndexChanged">
</asp:DropDownList>
您可以在DropDownLists的SelectedIndexChanged事件中執行此操作的最基本方法。 檢查此代碼。
<asp:DropDownList ID="DropDownList1" runat="server" onselectedindexchanged="DropDownList1_SelectedIndexChanged" Width="224px"
AutoPostBack="True" AppendDataBoundItems="true">
<asp:DropDownList ID="DropDownList2" runat="server"
onselectedindexchanged="DropDownList2_SelectedIndexChanged">
</asp:DropDownList>
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
//Load DropDownList2
}
protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{
//Load DropDownList3
}
我認為這是罪魁禍首:
cmd = new SqlCommand(query, con);
DataTable dt = Select(query);
cmd.ExecuteNonQuery();
ddtype.DataSource = dt;
我不知道該代碼應執行的操作,但是您似乎想為此創建一個SqlDataReader
,如此處和整個網絡中所述,如果您搜索“ SqlCommand DropDownList DataSource”,則說明:
cmd = new SqlCommand(query, con);
ddtype.DataSource = cmd.ExecuteReader();
或者你可以創建一個DataTable
作為解釋在這里 :
cmd = new SqlCommand(query, con);
SqlDataAdapter listQueryAdapter = new SqlDataAdapter(cmd);
DataTable listTable = new DataTable();
listQueryAdapter.Fill(listTable);
ddtype.DataSource = listTable;
使用下拉列表ddmanu
AutoPostBack="true"
將AutoPostBack
屬性設置為true
。
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