Exemplo n.º 1
0
        /// <summary>
        /// Returns a RegexValidationRule to be used for validating the specified TextBox.
        /// If the TextBox is not yet initialized, this method returns null.
        /// </summary>
        static RegexValidationRule GetRegexValidationRuleForTextBox(TextBox textBox)
        {
            if (!textBox.IsInitialized)
            {
                // If the TextBox.Text property is bound, but the TextBox is not yet
                // initialized, the property's binding can be null.  In that situation,
                // hook its Initialized event and verify the validation rule again when
                // that event fires.  At that point in time, the Text property's binding
                // will be non-null.
                EventHandler callback = null;
                callback = delegate
                {
                    textBox.Initialized -= callback;
                    VerifyRegexValidationRule(textBox);
                };
                textBox.Initialized += callback;
                return(null);
            }

            // Get the binding expression associated with the TextBox's Text property.
            BindingExpression expression = textBox.GetBindingExpression(TextBox.TextProperty);

            if (expression == null)
            {
                throw new InvalidOperationException(
                          "The TextBox's Text property must be bound for the RegexValidator to validate it.");
            }

            // Get the binding which owns the binding expression.
            Binding binding = expression.ParentBinding;

            if (binding == null)
            {
                throw new ApplicationException(
                          "Unexpected situation: the TextBox.Text binding expression has no parent binding.");
            }

            // Look for an existing instance of the RegexValidationRule class in the
            // binding.  If there is more than one instance in the ValidationRules
            // then throw an exception because we don't know which one to modify.
            RegexValidationRule regexRule = null;

            foreach (ValidationRule rule in binding.ValidationRules)
            {
                if (rule is RegexValidationRule)
                {
                    if (regexRule == null)
                    {
                        regexRule = rule as RegexValidationRule;
                    }
                    else
                    {
                        throw new InvalidOperationException(
                                  "There should not be more than one RegexValidationRule in a Binding's ValidationRules.");
                    }
                }
            }

            // If the TextBox.Text property's binding does not yet have an
            // instance of RegexValidationRule in its ValidationRules,
            // add an instance now and return it.
            if (regexRule == null)
            {
                regexRule = new RegexValidationRule();
                binding.ValidationRules.Add(regexRule);
            }

            return(regexRule);
        }