How to Implement IDataErrorInfo on ComboBox.Text when typing a value?

Question

When I type something in the Combobox, I want the validation check to occur and display the validation error. That doesn't seem to be happening with this code. How do I get the validation check to happen and validation error to show, when I pick a value from the combobox list or type a value in combobox?

<ComboBox x:Name="Cbx2" 
          IsEditable="True"
          Grid.Row="5" Grid.Column="2"                                
          HorizontalAlignment="Stretch"
          ItemsSource="{Binding ValuesList, Mode=OneWay}"   
          SelectedValue="{Binding SelectedCbxValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}"
          SelectionChanged="OnSelectionChanged"
          LostFocus="TxtBox_LostFocus">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding SelectedCbxValue, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}" />
            </StackPanel>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ComboBox>

Viewmodel

public class SOViewModel : ViewModelBase, IDataErrorInfo
{
    private ObservableCollection<string> _valuesList;

    public ObservableCollection<string> ValuesList
    {
        get => _valuesList;
        set => SetProperty(ref _valuesList, value);
    }

    private bool _isValid;
    public bool IsValid { get => _isValid; set => SetProperty(ref _isValid, value); }

    private string _selectedCbxValue;
    public string SelectedCbxValue { get => _selectedCbxValue; set => SetProperty(ref _selectedCbxValue, value); }

#region IDataErrorInfo properties
    private string _error;
    public string Error { get => _error; set => SetProperty(ref _error, value); }

    public string this[string propName]
    {
        get
        {
            return ValidateProperty(propName);
        }
    }

    private string ValidateProperty(string propName)
    {
        string errorMessaage = string.Empty;
            
        bool ValidateValue(string valueToValid)
        {
            // validation code goes here

            return true;
        }

        if (propName == nameof(SelectedCbxValue))
        {
           IsValid = IsValid && ValidateValue(SelectedCbxValue);
        }

        if (string.IsNullOrEmpty(errorMessaage)) { Error = null; }
        else { Error = errorMessaage; }

        return errorMessaage;
    }
#endregion

}

Answer 1

<ComboBox x:Name="Cbx2" 
          IsEditable="True"
          Grid.Row="5" Grid.Column="2"                                
          HorizontalAlignment="Stretch"
          ItemsSource="{Binding ValuesList, Mode=OneWay}"   
          SelectedValue="{Binding SelectedCbxValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True, ValidatesOnDataErrors=True}"
          SelectionChanged="OnSelectionChanged"
          LostFocus="TxtBox_LostFocus">
          <ComboBox.Text>
               <Binding Path="SelectedCbxValue" 
                        UpdateSourceTrigger="PropertyChanged" 
                        NotifyOnValidationError="True"
                        ValidatesOnDataErrors="True" 
                        Mode="TwoWay">
               </Binding>
          </ComboBox.Text>
</ComboBox>

Google led me here and it was helpful: WPF Editable ComboBox validation