How to enable a button when a user types into a textbox

Question

What is the simplest way in WPF to enable a Button when the user types something into a TextBox?

Answer 1

Use the Simple Command

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
            };  
    }            

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }     
}

For more information see Marlon Grechs SimpleCommand

Also check out the MVVM 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.