Question

When SelectedItem.DT throws an error Validation_Error is not called? DT is a DataTable from a SQL query and I want to display the SQL error if the TSQL fails. I guess I could build a DataTable and put the ex.msg in the table. But I would rather call Validation_Error.

    <DataGrid Grid.Row="1" Grid.Column="0" AutoGenerateColumns="True"  
              ItemsSource="{Binding ElementName=cbReports, Path=SelectedItem.DT, ValidatesOnExceptions=True, NotifyOnValidationError=True, NotifyOnSourceUpdated=True}"
              Validation.Error="Validataion_Error" />

This TextBox (on another page) does call Validation_Error when an error is thrown in set.

    <TextBox Text="{Binding Path=DF.FieldValue, Mode=TwoWay, ValidatesOnExceptions=True, NotifyOnValidationError=True}"
             Validation.Error="Validataion_Error"/>

Answer 1

DataTable is not implement IDataErrorInfo then it isn’t do any validation error automatically for you. I always transform DataTable to ObservableCollection of my class that implement IDataErrorInfo.

public class MyClass : IDataErrorInfo
{
    //..
}

// Use ObservableCollection instead of DataTable
ObservableCollection<MyClass> MyDataGridItemsSource { get; set; }

I guess that the reason your textbox binding works is DF in your DF.FieldValue is implement IDataErrorInfo.