Question

I have a page with a number of fields on it that I’m using to create a new class record called Account. One of the fields is a currency code that is set via a combobox. The combobox is bound to a datatable with an id and a description. I’m trying to use binding so that the selectedvalue of the combobox automatically updates the currency id of the Account class. So far no joy…

Class definition:

class Account : IDataErrorInfo
{
    public String Name { get; set; }
    public int CurrencyID { get; set; }
    public int BankID { get; set; }
    public String AccountNumber { get; set; }
    public decimal OpeningBalance { get; set; }

 ... other definitions for validation handling ...

}

Combobox definition:

<ComboBox x:Name="cboCurrency" Grid.Column="1" Grid.Row="1" Width="250" HorizontalAlignment="Left" 
     SelectedValue="{Binding Path=Account.CurrencyID, UpdateSourceTrigger=LostFocus, ValidatesOnDataErrors=True, NotifyOnValidationError=true}"
     ToolTip="{Binding ElementName=cboCurrency, Path=(Validation.Errors)[0].ErrorContent}"/>

Page constructor:

public AccountAdd()
{
    InitializeComponent();

    base.DataContext = new Account();

    // Load the Currency combo with the list of currencies
    //
    cboCurrency.DisplayMemberPath = "Name";
    cboCurrency.SelectedValuePath = "_id";
    cboCurrency.ItemsSource = _DBUtils.getCurrencyList().DefaultView;


}

Save Code:

private void btnAccountOK_Click(object sender, RoutedEventArgs e)
{
    Account newAccountRec = (Account)base.DataContext;

    int newid = _DBUtils.AddAccount(newAccountRec);
}

Answer 1

Since the ComboBox’s DataContext is set to an Account instance, its SelectedValue should bind to CurrencyID, not Account.CurrencyID:

<ComboBox SelectedValue="{Binding Path=CurrencyID, ...}" ... />

Also (if your datatable is a DataTable) create a collection of objects with appropriate properties from each table row for the ComboBox’s items, as suggested by blindmeis:

cboCurrency.DisplayMemberPath = "Name";  
cboCurrency.SelectedValuePath = "Id";  
cboCurrency.ItemsSource =
    _DBUtils.getCurrencyList().Rows.Cast<DataRow>().Select(
        row => new { Name = row["Name"], Id = row["_id"] });