Unexpected red border (validation error) on DataGrid when selecting blank row

Question

When I select (by clicking or by keyboard) blank row on my DataGrid (when I want to add new row), unexpected validation error occurs (but with no exception) - the border of datagrid changes to red color, as you can see on the image below. When I click second time on blank row, the red border dissapears. Everything other works fine, the new row is added. Besides, I don't have any validation rules. And when I make a row with empty text, value is valid.

I don't want this behavior and this red border, anybody knows, why this happens and how to fix it? Why and where some validation fails?

Below I append some source code:

DataGrid definition in xaml:

    <DataGrid IsSynchronizedWithCurrentItem="True" DisplayMemberPath="Name"   ItemsSource="{Binding Path=ConfigFiles}" SelectedItem="{Binding Path=SelectedConfigFile}"                Grid.Column="1" Height="87" Margin="0,26,11,32" Style="{DynamicResource DataGridStyle}">         <DataGrid.Columns>             <DataGridTextColumn Width="1*" Binding="{Binding Name}" />         </DataGrid.Columns>     </DataGrid> 

My ViewModel's part:

public class ManageModulesVM : BaseVM  // Implements INotifyPropertyChanged {     // ...      public ObservableCollection<ConfigFile> ConfigFiles     {         get { return selectedModule == null ? null : selectedModule.ConfigFiles; }         set         {             selectedModule.ConfigFiles = value;             OnPropertyChanged(() => ConfigFiles);         }     }      public ConfigFile SelectedConfigFile     {         get { return selectedModule == null ? null : selectedModule.SelectedConfigFile; }         set         {             if (value != null)             {                 selectedModule.SelectedConfigFile = value;             }             OnPropertyChanged(() => SelectedConfigFile);             OnPropertyChanged(() => Parameters);         }     }      // ... } 

ConfigFile class:

public class ConfigFile {     public string Name { get; set; }     public IList<Parameter> Parameters { get; set; }      public ConfigFile() { Name = ""; Parameters = new List<Parameter>(); } } 

Edit: After further investigation I know, that SelectedItem Binding is causing problems (when I remove this binding, validation error stops to appear), but I still don't know why and how to fix this.

Answer 1

I've found my own solution to this question. I've written a value converter and tied it to the binding:

(SelectedItem="{Binding Path=SelectedConfigFile,Converter={StaticResource configFileConverter}}")

The converter class:

namespace Converters {     public class SelectedConfigFileConverter : IValueConverter     {         public object Convert(object value, Type targetType, object parameter, CultureInfo culture)         {             return value;         }          public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)         {             if(value is ConfigFile)                 return value;             return null;         }     } } 

Define resource in resources.xaml file (or in any other resources place):

<ResourceDictionary (...) xmlns:conv="clr-namespace:Converters" >     <conv:SelectedConfigFileConverter x:Key="configFileConverter" /> </ResourceDictionary> 

The advantage of this solution is that the SelectedConfigFile property's type did't changed (to the general object type) so it is still strongly typed.