Reputation: 1181
I have a WPF application with a number of comboboxes that tie together. When I switch comboboxx #1, combobox #2 switches, etc.
Here is the xaml for the 2 comboboxes:
<ComboBox Grid.Row="1" Height="23" HorizontalAlignment="Right" Margin="0,12,286,0" ItemsSource="{Binding}" Name="CboDivision" VerticalAlignment="Top" Width="120" SelectionChanged="CboDivision_SelectionChanged" />
<ComboBox Height="23" HorizontalAlignment="Right" Margin="0,9,32,0" Name="CboCustomerList" ItemsSource="{Binding}" VerticalAlignment="Top" Width="120" SelectionChanged="CboCustomerList_SelectionChanged" Grid.Row="1" />
CboDivision gets populated at the beginning and doesnt need a reset. HEre is the code that calls the change in division, which should trigger a change in customer:
private void CboDivision_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
division = CboDivision.SelectedValue.ToString();
CboCustomerList.ItemsSource = null;
BackgroundWorker customerWorker = new BackgroundWorker();
customerWorker.DoWork += new DoWorkEventHandler(FillCustomers);
customerWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(customerWorker_RunWorkerCompleted);
FillCustomers(null, null);
}
When I do an index change it calls a backgroundworker which calls the following code:
private void FillCustomers(object sender, DoWorkEventArgs e)
{
string connectionString = Settings.Default.ProdConnectionString;
SqlConnection connection = new SqlConnection(connectionString);
SqlCommand SqlCmd = new SqlCommand();
Mouse.OverrideCursor = System.Windows.Input.Cursors.Wait;
SqlCmd.CommandType = CommandType.StoredProcedure;
SqlCmd.Parameters.Add("@division", SqlDbType.NVarChar).Value = division;
SqlCmd.Connection = connection;
SqlCmd.CommandText = "sp_GetCustomers";
SqlDataReader reader = null;
connection.Open();
reader = SqlCmd.ExecuteReader();
List<string> result = new List<string>();
while (reader.Read())
{
result.Add(reader["NAME"].ToString());
}
e.Result = result;
}
The problem is that i am unable to switch selections on CboDivision and have CboCustomerList clear and reload new values into it. Is it the way I'm binding the values in the xaml? How can I have a change in CboDivision cause a clearing of CboCustomerList items, then the execution of the filling routine?
i am currently resetting the combobox with:
CboCustomerList.SelectedIndex = -1;
but this just appends the new cbocustomerlist query to the end I also tried
CboCustomerList.Items.Clear()
but that just returns a null reference error after the box is refilled and the user selects an item.
Upvotes: 7
Views: 418
Reputation: 542
replace the wrong FillCustomers(null, null);
code
with: customerWorker.RunWorkerAsync();
Upvotes: 1
Reputation: 864
Well, you didn't post all of your code, but one problem is that you are not invoking your worker thread.
Replace FillCustomers(null, null)
with customerWorker.RunWorkerAsync()
.
private void CboDivision_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
division = CboDivision.SelectedValue.ToString();
CboCustomerList.ItemsSource = null;
BackgroundWorker customerWorker = new BackgroundWorker();
customerWorker.DoWork += new DoWorkEventHandler(FillCustomers);
customerWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(customerWorker_RunWorkerCompleted);
customerWorker.RunWorkerAsync(); // <-- this
}
Let me know if this helps. If there is still more problem, please post the rest of your code.
Upvotes: 3
Reputation: 16338
There are details of code you didn't show. However, here is an example that works: two combos, what that is populated at the beginning, and a second that is populated each time the selection changes in the first. Notice that the data is fetched in a background worker, just as in your case.
XAML
<Window x:Class="CombosRefresh.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<ComboBox Name="CboDivisions" ItemsSource="{Binding}" Grid.Row="0" Margin="5" />
<ComboBox Name="CboList" ItemsSource="{Binding}" Grid.Row="1" Margin="5" />
</Grid>
</Window>
C#
public partial class MainWindow : Window
{
private BackgroundWorker bw = new BackgroundWorker();
public MainWindow()
{
InitializeComponent();
CboDivisions.DataContext = new List<string>() { "red", "blue", "green" };
CboDivisions.SelectionChanged += CboDivisions_SelectionChanged;
bw.DoWork += bw_DoWork;
bw.RunWorkerCompleted += bw_RunWorkerCompleted;
}
void CboDivisions_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var division = CboDivisions.SelectedValue as string;
bw.RunWorkerAsync(division);
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
CboList.DataContext = e.Result as List<string>;
}
void bw_DoWork(object sender, DoWorkEventArgs e)
{
var division = e.Argument as string;
var r = new Random();
var result = new List<string>();
for(int i = 0; i < r.Next(0, 10); ++i)
{
result.Add(string.Format("{0} #{1}", division, i+1));
}
e.Result = result;
}
}
Upvotes: 3