Textbox binding update in WPF

MessageText property gets updated only when I hit another control. What is more if I press any button it's Click handler isn't executed and the MessageText set is executed instead. I've broken my head.

<TextBox x:Name="messageText" Grid.Row="1" Grid.Column="0"
         TextWrapping="Wrap" Text="{Binding Path=MessageText, Mode=TwoWay}"/>

private void ChatView_Loaded(object sender, RoutedEventArgs e)
{
    DataContext = viewModel;
}

public string MessageText
{
    get
    {
        return this.messageText;
    }
    set
    {
        this.messageText = value;
        OnProperyChanged("MessageText");
    }
}

You can adjust UpdateSourceTrigger to PropertyChanged

<TextBox x:Name="messageText" Grid.Row="1" Grid.Column="0"
                 TextWrapping="Wrap" Text="{Binding Path=MessageText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>