feat: Add support for multiple Reply-Tos

src/SendGrid/Helpers/Mail/SendGridMessage.cs

@@ -138,6 +138,12 @@ public class SendGridMessage
         [JsonProperty(PropertyName = "reply_to")]
         public EmailAddress ReplyTo { get; set; }
 
+        /// <summary>
+        /// Gets or sets a list of objects of email objects containing the email address and name of the individuals who should receive responses to your email.
+        /// </summary>
+        [JsonProperty(PropertyName = "reply_to_list", IsReference = false)]
+        public List<EmailAddress> ReplyTos { get; set; }
+
         /// <summary>
         /// Add a recipient email.
         /// </summary>
@@ -318,6 +324,50 @@ public void AddHeaders(Dictionary<string, string> headers, int personalizationIn
                     personalization.Headers.Union(headers).ToDictionary(pair => pair.Key, pair => pair.Value);
         }
 
+        /// <summary>
+        /// Add a reply-to email.
+        /// </summary>
+        /// <param name="email">Specify the recipient's email.</param>
+        /// <param name="name">Specify the recipient's name.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown when the email parameter is null or whitespace</exception>
+        public void AddReplyTo(string email, string name = null)
+        {
+            if (string.IsNullOrWhiteSpace(email))
+                throw new ArgumentNullException("email");
+
+            this.AddReplyTo(new EmailAddress(email, name));
+        }
+
+        /// <summary>
+        /// Add a reply-to email.
+        /// </summary>
+        /// <param name="email">An email recipient that may contain the recipient’s name, but must always contain the recipient’s email.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown when the email parameter is null</exception>
+        public void AddReplyTo(EmailAddress email)
+        {
+            if (email == null)
+                throw new ArgumentNullException("email");
+
+            AddReplyTos(new List<EmailAddress> { email });
+        }
+
+        /// <summary>
+        /// Add reply-to recipients.
+        /// </summary>
+        /// <param name="emails">A list of reply-to recipients. Each email object within this array may contain the recipient’s name, but must always contain the recipient’s email.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown when the emails parameter is null</exception>
+        /// <exception cref="System.InvalidOperationException">Thrown when the emails parameter is empty</exception>
+        public void AddReplyTos(List<EmailAddress> emails)
+        {
+            if (emails == null)
+                throw new ArgumentNullException("emails");
+            if (emails.Count == 0)
+                throw new InvalidOperationException("Sequence contains no elements");
+
+            if (ReplyTos == null) ReplyTos = new List<EmailAddress>();
+            ReplyTos.AddRange(emails);
+        }
+
         /// <summary>
         /// Add a substitution to the email.
         /// You may not include more than 100 substitutions per personalization object, and the total collective size of your substitutions may not exceed 10,000 bytes per personalization object.

tests/SendGrid.Tests/Integration.cs

@@ -2217,6 +2217,23 @@ public void TestSetReplyTo()
             Assert.Equal("{\"reply_to\":{\"name\":\"Test User2\",\"email\":\"[email protected]\"}}", msg.Serialize());
         }
 
+        [Fact]
+        public void TestAddReplyTos()
+        {
+            var msg = new SendGridMessage();
+            msg.AddReplyTo("[email protected]", "Test User2");
+            Assert.Equal("{\"reply_to_list\":[{\"name\":\"Test User2\",\"email\":\"[email protected]\"}]}", msg.Serialize());
+
+            msg = new SendGridMessage();
+            msg.AddReplyTo("[email protected]", "Test User1");
+            msg.AddReplyTo("[email protected]", "Test User2");
+            Assert.Equal("{\"reply_to_list\":[{\"name\":\"Test User1\",\"email\":\"[email protected]\"},{\"name\":\"Test User2\",\"email\":\"[email protected]\"}]}", msg.Serialize());
+
+            msg = new SendGridMessage();
+            msg.AddReplyTos(new List<EmailAddress> { new EmailAddress() { Email = "[email protected]" }, new EmailAddress() { Email = "[email protected]", Name = "Test User2" } });
+            Assert.Equal("{\"reply_to_list\":[{\"email\":\"[email protected]\"},{\"name\":\"Test User2\",\"email\":\"[email protected]\"}]}", msg.Serialize());
+        }
+
         [Fact]
         public void TestSetGlobalSubject()
         {

tests/SendGrid.Tests/PreSendEmailValidation/WhenCreatingASendGridMessage.cs

@@ -48,5 +48,19 @@ public void WithANullCarbonCopyThenAnExceptionIsThrown()
             var sendGridMessage = MailHelper.CreateSingleEmail(new EmailAddress(), new EmailAddress(), string.Empty, string.Empty, string.Empty);
             Assert.Throws<ArgumentNullException>(() => { sendGridMessage.AddCc(null, 0); });
         }
+
+        [Fact]
+        public void WithAnEmptyListOfReplyTosThenAnExceptionIsThrown()
+        {
+            var sendGridMessage = MailHelper.CreateSingleEmail(new EmailAddress(), new EmailAddress(), string.Empty, string.Empty, string.Empty);
+            Assert.Throws<InvalidOperationException>(() => { sendGridMessage.AddReplyTos(new List<EmailAddress>()); });
+        }
+
+        [Fact]
+        public void WithANullListOfReplyTosThenAnExceptionIsThrown()
+        {
+            var sendGridMessage = MailHelper.CreateSingleEmail(new EmailAddress(), new EmailAddress(), string.Empty, string.Empty, string.Empty);
+            Assert.Throws<ArgumentNullException>(() => { sendGridMessage.AddReplyTos(null); });
+        }
     }
 }