Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.ComponentModel.DataAnnotations/DataAnnotations/PhoneAttribute.cs

@@ -0,0 +1,25 @@
+namespace System.ComponentModel.DataAnnotations {
+    using System;
+    using System.ComponentModel.DataAnnotations.Resources;
+    using System.Text.RegularExpressions;
+
+    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
+    public sealed class PhoneAttribute : DataTypeAttribute {
+        // see unit tests for examples
+        private static Regex _regex = new Regex(@"^(\+\s?)?((?<!\+.*)\(\+?\d+([\s\-\.]?\d+)?\)|\d+)([\s\-\.]?(\(\d+([\s\-\.]?\d+)?\)|\d+))*(\s?(x|ext\.?)\s?\d+)?$", RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.ExplicitCapture);
+
+        public PhoneAttribute()
+            : base(DataType.PhoneNumber) {
+            ErrorMessage = DataAnnotationsResources.PhoneAttribute_Invalid;
+        }
+
+        public override bool IsValid(object value) {
+            if (value == null) {
+                return true;
+            }
+
+            string valueAsString = value as string;
+            return valueAsString != null && _regex.Match(valueAsString).Length > 0;
+        }
+    }
+}