这似乎是一个常见问题。我尝试了不同的解决方案，但它仍然无效。这是我的代码。
HTML：
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == UITableViewCellEditingStyle.delete {
let managedObjectContext: NSManagedObjectContext = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext;
let managedObject: NSManagedObject = fetchedResultsController.object(at: indexPath) as! NSManagedObject;
managedObjectContext.delete(managedObject);
do {
try managedObjectContext.save();
tableView.deleteRows(at: [indexPath], with: UITableViewRowAnimation.fade);
} catch {
// Error occured while deleting objects
}
} else if editingStyle == UITableViewCellEditingStyle.insert {
}
}
功能：OnSelectedIndexChanged
<div class="form-group">
<label for="exampleInputEmail1">Artist *</label>
<asp:DropDownList ID="artistDropdown" runat="server" CssClass="form-control" AutoPostBack="True" OnSelectedIndexChanged="artistDropdown_SelectedIndexChanged" ViewStateMode="Enabled"></asp:DropDownList>
<asp:TextBox ID="mytest" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ControlToValidate="artistDropdown" SetFocusOnError="true" ErrorMessage="Required Field" Font-Bold="True" Font-Names="Arial" Font-Size="X-Small" ForeColor="Red"></asp:RequiredFieldValidator>
<asp:Label ID="lblMessage" runat="server" CssClass="help-block" Visible="False">Cant select Artist with no Manager</asp:Label>
</div>
我在protected void artistDropdown_SelectedIndexChanged(object sender, EventArgs e)
{
string selectedArtist = artistDropdown.SelectedValue;
mytest.Text = selectedArtist;
string query = "Select [Manager ID] from Artist Where ID = '" + selectedArtist + "'";
string myConnection = dbController.connectionString;
SqlConnection conn = new SqlConnection(myConnection);
SqlCommand cmd = new SqlCommand(query, conn);
conn.Open();
object obj = cmd.ExecuteScalar();
if (obj is System.DBNull)
{
artistDropdown.SelectedValue = "";
lblMessage.Visible = true;
}
else
{
lblMessage.Visible = false;
}
conn.Close();
}
函数中加载DropDownList，并为DropDownList设置Page_Load()。
我还创建了一个TextBox，它从DropDownList设置为selectedValue，以检查OnSelectedIndexChanged是否正在触发。但是文本框仍然是空的。
我做错了什么？