Fixed Verifiy email using regex and modified Login action

src/Fan.Web/Controllers/AuthController.cs

@@ -52,7 +52,7 @@ public async Task<IActionResult> Login([FromBody] LoginViewModel loginUser)
                 return BadRequest("Invalid credentials!");
 
             // sign user in
-            var result = await _signInManager.PasswordSignInAsync(user.UserName, loginUser.Password,
+            var result = await _signInManager.PasswordSignInAsync(user, loginUser.Password,
                 loginUser.RememberMe, lockoutOnFailure: false);
 
             if (!result.Succeeded)

src/Fan/Helpers/RegexUtilities.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Globalization;
+using System.Text.RegularExpressions;
+
+namespace Fan.Helpers
+{
+    /// <summary>
+    /// A util class that uses regular expression to verify if a string is in valid email format.
+    /// </summary>
+    /// <remarks>
+    /// https://docs.microsoft.com/en-us/dotnet/standard/base-types/how-to-verify-that-strings-are-in-valid-email-format
+    /// </remarks>
+    public static class RegexUtilities
+    {
+        public static bool IsValidEmail(string strIn)
+        {
+            if (String.IsNullOrEmpty(strIn))
+                return false;
+
+            // Use IdnMapping class to convert Unicode domain names.
+            try
+            {
+                strIn = Regex.Replace(strIn, @"(@)(.+)$", DomainMapper,
+                                      RegexOptions.None, TimeSpan.FromMilliseconds(200));
+                if(string.IsNullOrEmpty(strIn))
+                    return false;
+            }
+            catch (Exception ex)
+            {
+                if(ex is RegexMatchTimeoutException || ex is ArgumentNullException)
+                    return false;
+            }
+            // Return true if strIn is in valid email format.
+            try
+            {
+                return Regex.IsMatch(strIn,
+                      @"^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
+                      @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-0-9a-z]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$",
+                      RegexOptions.IgnoreCase, TimeSpan.FromMilliseconds(250));
+            }
+            catch (RegexMatchTimeoutException)
+            {
+                return false;
+            }
+        }
+
+        private static string DomainMapper(Match match)
+        {
+            // IdnMapping class with default property values.
+            IdnMapping idn = new IdnMapping();
+
+            string domainName = match.Groups[2].Value;
+            try
+            {
+                domainName = idn.GetAscii(domainName);
+            }
+            catch (ArgumentException)
+            {
+                return null; 
+            }
+            return match.Groups[1].Value + domainName;
+        }
+    }
+}

src/Fan/Membership/UserService.cs

@@ -1,7 +1,6 @@
-using Microsoft.AspNetCore.Identity;
+using Fan.Helpers;
+using Microsoft.AspNetCore.Identity;
 using Microsoft.Extensions.Logging;
-using System;
-using System.Net.Mail;
 using System.Threading.Tasks;
 
 namespace Fan.Membership
@@ -10,7 +9,6 @@ public class UserService : IUserService
     {
         private readonly UserManager<User> _userManager;
         private readonly ILogger<UserService> _logger;
-
         public UserService(UserManager<User> userManager,
             ILogger<UserService> logger)
         {
@@ -25,18 +23,7 @@ public class UserService : IUserService
         /// <returns></returns>
         public async Task<User> FindByEmailOrUsernameAsync(string emailOrUsername)
         {
-            bool isEmail;
-            try
-            {
-                new MailAddress(emailOrUsername);
-                isEmail = true;
-            }
-            catch (FormatException)
-            {
-                isEmail = false;
-            }
-
-            // get user
+            bool isEmail = RegexUtilities.IsValidEmail(emailOrUsername);
             return isEmail ? await _userManager.FindByEmailAsync(emailOrUsername) :
                 await _userManager.FindByNameAsync(emailOrUsername);
         }

test/Fan.UnitTests/Helpers/RegexUtilitiesTest.cs

@@ -0,0 +1,40 @@
+using Fan.Helpers;
+using Xunit;
+
+namespace Fan.UnitTests.Helpers
+{
+    /// <summary>
+    /// Test for <see cref="RegexUtilities"/> class.
+    /// </summary>
+    public class RegexUtilitiesTest
+    {
+        /// <summary>
+        /// Test cases for <see cref="RegexUtilities.IsValidEmail(string)"/> method.
+        /// </summary>
+        /// <param name="email"></param>
+        /// <param name="expected"></param>
+        /// <remarks>
+        /// Test data provided by https://docs.microsoft.com/en-us/dotnet/standard/base-types/how-to-verify-that-strings-are-in-valid-email-format#compiling-the-code
+        /// </remarks>
+        [Theory]
+        [InlineData("david.jones@proseware.com", true)]
+        [InlineData("d.j@server1.proseware.com", true)]
+        [InlineData("jones@ms1.proseware.com", true)]
+        [InlineData("j.@server1.proseware.com", false)]
+        [InlineData("j@proseware.com9", true)]
+        [InlineData("js#internal@proseware.com", true)]
+        [InlineData("j_9@[129.126.118.1]", true)]
+        [InlineData("j..s@proseware.com", false)]
+        [InlineData("js*@proseware.com", false)]
+        [InlineData("js@proseware..com", false)]
+        [InlineData("js@proseware.com9", true)]
+        [InlineData("j.s@server1.proseware.com", true)]
+        [InlineData(@"""j\""s\""""@proseware.com", true)]
+        [InlineData("js@contoso.中国", true)]
+        [InlineData("username", false)]
+        public void IsValidEmail_Test(string email, bool expected)
+        {
+            Assert.Equal(expected, RegexUtilities.IsValidEmail(email));
+        }
+    }
+}