Adds MaxAge Property to CookieOptions and CookieBuilder

src/Microsoft.AspNetCore.Http.Abstractions/CookieBuilder.cs

@@ -67,6 +67,11 @@ public virtual string Name
         /// </summary>
         public virtual TimeSpan? Expiration { get; set; }
 
+        /// <summary>
+        /// Gets or sets the max-age for the cookie.
+        /// </summary>
+        public virtual TimeSpan? MaxAge { get; set; }
+
         /// <summary>
         /// Creates the cookie options from the given <paramref name="context"/>.
         /// </summary>
@@ -92,6 +97,7 @@ public virtual CookieOptions Build(HttpContext context, DateTimeOffset expiresFr
                 Path = Path ?? "/",
                 SameSite = SameSite,
                 HttpOnly = HttpOnly,
+                MaxAge = MaxAge,
                 Domain = Domain,
                 Secure = SecurePolicy == CookieSecurePolicy.Always || (SecurePolicy == CookieSecurePolicy.SameAsRequest && context.Request.IsHttps),
                 Expires = Expiration.HasValue ? expiresFrom.Add(Expiration.Value) : default(DateTimeOffset?)

src/Microsoft.AspNetCore.Http.Features/CookieOptions.cs

@@ -53,5 +53,11 @@ public CookieOptions()
         /// </summary>
         /// <returns>true if a cookie must not be accessible by client-side script; otherwise, false.</returns>
         public bool HttpOnly { get; set; }
+
+        /// <summary>
+        /// Gets or sets the max-age for the cookie.
+        /// </summary>
+        /// <returns>The max-age date and time for the cookie.</returns>
+        public TimeSpan? MaxAge { get; set; }
     }
 }

src/Microsoft.AspNetCore.Http/Internal/ResponseCookies.cs

@@ -61,6 +61,7 @@ public void Append(string key, string value, CookieOptions options)
                 Domain = options.Domain,
                 Path = options.Path,
                 Expires = options.Expires,
+                MaxAge = options.MaxAge,
                 Secure = options.Secure,
                 SameSite = (Net.Http.Headers.SameSiteMode)options.SameSite,
                 HttpOnly = options.HttpOnly

test/Microsoft.AspNetCore.Http.Abstractions.Tests/CookieBuilderTests.cs

@@ -38,6 +38,16 @@ public void ComputesExpiration()
             Assert.Equal(now.AddHours(1), options.Expires);
         }
 
+        [Fact]
+        public void ComputesMaxAge()
+        {
+            Assert.Null(new CookieBuilder().Build(new DefaultHttpContext()).MaxAge);
+
+            var now = TimeSpan.FromHours(1);
+            var options = new CookieBuilder { MaxAge = now }.Build(new DefaultHttpContext());
+            Assert.Equal(now, options.MaxAge);
+        }
+
         [Fact]
         public void CookieBuilderPreservesDefaultPath()
         {

test/Microsoft.AspNetCore.Http.Tests/ResponseCookiesTest.cs

@@ -2,9 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Text;
 using Microsoft.AspNetCore.Http.Internal;
-using Microsoft.Extensions.ObjectPool;
 using Microsoft.Net.Http.Headers;
 using Xunit;
 
@@ -74,6 +72,23 @@ public void NoParamsDeleteRemovesCookieCreatedByAdd()
             Assert.Contains("expires=Thu, 01 Jan 1970 00:00:00 GMT", cookieHeaderValues[0]);
         }
 
+        [Fact]
+        public void ProvidesMaxAgeWithCookieOptionsArgumentExpectMaxAgeToBeSet()
+        {
+            var headers = new HeaderDictionary();
+            var cookies = new ResponseCookies(headers, null);
+            var cookieOptions = new CookieOptions();
+            var maxAgeTime = TimeSpan.FromHours(1);
+            cookieOptions.MaxAge = TimeSpan.FromHours(1);
+            var testcookie = "TestCookie";
+
+            cookies.Append(testcookie, testcookie, cookieOptions);
+
+            var cookieHeaderValues = headers[HeaderNames.SetCookie];
+            Assert.Equal(1, cookieHeaderValues.Count);
+            Assert.Contains($"max-age={maxAgeTime.TotalSeconds.ToString()}", cookieHeaderValues[0]);
+        }
+
         public static TheoryData EscapesKeyValuesBeforeSettingCookieData
         {
             get