How to checks that whether UserControl is Valid or not

I have a textbox inside usercontrol that implements ValidationRule and it is working fine, now in the window where i'm using this control has one button, and i want that button to be disabled if text开发者_开发技巧box inside usercontrol is not valid

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The trick here is to use a Command, instead of the click event. A command contains logic to determine whether the command is valid, as well as the actual code to run when the command is executed.

We create a command, and bind the button to it. The button will automatically become disabled if Command.CanExecute() returns false. There are a bunch of benefits to using the command framework, but I won't go into those here.

Below is an example which should get you started. The XAML:

<StackPanel>
    <Button Content="OK" Command="{Binding Path=Cmd}">
    </Button>
    <TextBox Name="textBox1">
        <TextBox.Text>
            <Binding Path="MyVal" UpdateSourceTrigger="PropertyChanged" >
                <Binding.ValidationRules>
                    <local:MyValidationRule/>
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>
</StackPanel>

The UserControl code-behind (this is probably similar to what you already have, but I've included it to show how the command is created):

public partial class UserControl1 : UserControl
{
    private MyButtonCommand _cmd;
    public MyButtonCommand Cmd
    {
        get { return _cmd; }
    }

    private string _myVal;
    public string MyVal
    {
        get { return _myVal; }
        set { _myVal = value; }
    }

    public UserControl1()
    {
        InitializeComponent();
        _cmd = new MyButtonCommand(this);
        this.DataContext = this;
    }
}

The Command class. The purpose of this class is to decide whether the command is valid using the Validation system, and to refresh it's state when the TextBox.Text changes:

public class MyButtonCommand : ICommand
{
    public bool CanExecute(object parameter)
    {
        if (Validation.GetHasError(myUserControl.textBox1))
            return false;
        else
            return true;
    }

    public event EventHandler CanExecuteChanged;
    private UserControl1 myUserControl;

    public MyButtonCommand(UserControl1 myUserControl)
    {
        this.myUserControl = myUserControl;
        myUserControl.textBox1.TextChanged += new TextChangedEventHandler(textBox1_TextChanged);
    }

    void textBox1_TextChanged(object sender, TextChangedEventArgs e)
    {
        if (CanExecuteChanged != null)
            CanExecuteChanged(this, EventArgs.Empty);
    }

    public void Execute(object parameter)
    {
        MessageBox.Show("hello");
    }
}