Enable a button when a textbox got text

What is the simplest way in WPF to enable a button when the user types something in a textbox?

Thanks!

From stackoverflow

• Add a callback to the TextBox that fires on every stroke. Test for emptiness in such callback and enable/disable the button.

• Use the Simple Command

  <TextBox Text={Binding Path=TitleText}/>
  
  <Button Command="{Binding Path=ClearTextCommand}" Content="Clear Text"/>
  

  Here is the sample code in the View Model

  public class MyViewModel : INotifyPropertyChanged
  {
      public ICommand ClearTextCommand { get; private set; }
  
      private string _titleText; 
      public string TitleText
      {
          get { return _titleText; }
          set
          {
              if (value == _titleText)
                  return;
  
              _titleText = value;
              this.OnPropertyChanged("TitleText");
          }
      }   
  
      public MyViewModel()
      {
          ClearTextCommand = new SimpleCommand
              {
                  ExecuteDelegate = x => TitleText="",
                  CanExecuteDelegate = x => TitleText.Length > 0
              };  
      }
  
      #region - INotifyPropertyChanged Members -
  
      public event PropertyChangedEventHandler PropertyChanged;
  
      protected void OnPropertyChanged(string propertyName)
      {
          PropertyChangedEventHandler handler = this.PropertyChanged;
          if (handler != null)
              handler(this, new PropertyChangedEventArgs(propertyName));
      }
  
      #endregion   
  }
  

  For more information see Marlon Grechs SimpleCommand

  Also check out the M-V-VM Project Template/Toolkit from http://blogs.msdn.com/llobo/archive/2009/05/01/download-m-v-vm-project-template-toolkit.aspx. It uses the DelegateCommand for commanding and it should be a great starting template for any project.

• IF you were not using Commands, another alternative is using a Converter.

  For example, using a generic Int to Bool converter:

    [ValueConversion(typeof(int), typeof(bool))]
    public class IntToBoolConverter : IValueConverter
    {
      #region IValueConverter Members
  
      public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
      {
        try
        {
          return (System.Convert.ToInt32(value) > 0);
        }
        catch (InvalidCastException)
        {
          return DependencyProperty.UnsetValue;
        }
      }
  
      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
      {
        return System.Convert.ToBoolean(value) ? 1 : 0;
      }
  
      #endregion
    }
  

  Then on the buttons IsEnabled property:

  <Button IsEnabled={Binding ElementName=TextBoxName, Path=Text.Length, Converter={StaticResource IntToBoolConverter}}/>
  

  HTH,

  Dennis

• Use a trigger!

  <TextBox x:Name="txt_Titel />
  <Button Content="Transfer" d:IsLocked="True">
    <Button.Style>
      <Style>
        <Style.Triggers>
          <DataTrigger Binding="{Binding ElementName=txt_Titel, Path=Text}" Value="">
           <Setter Property="Button.IsEnabled" Value="false"/>
          </DataTrigger>
        </Style.Triggers>
      </Style>
    </Button.Style>
  </Button>
  

• Why is everyone making things so complicated!

      <TextBox x:Name="TB"/>
      <Button IsEnabled="{Binding ElementName=TB,Path=Text.Length}">Test</Button>
  

  Nothing else needed......