Consistently use CreateProxyUri in WebProxy ctors (#62338)

Author: MihaZupan

src/libraries/System.Net.WebProxy/src/System/Net/WebProxy.cs

@@ -35,7 +35,7 @@ public WebProxy(Uri? Address, bool BypassOnLocal, string[]? BypassList, ICredent
         }
 
         public WebProxy(string Host, int Port)
-            : this(new Uri(string.Create(CultureInfo.InvariantCulture, $"http://{Host}:{Port}")), false, null, null)
+            : this(CreateProxyUri(Host, Port), false, null, null)
         {
         }
 
@@ -102,10 +102,27 @@ public bool UseDefaultCredentials
             return IsBypassed(destination) ? destination : Address;
         }
 
-        private static Uri? CreateProxyUri(string? address) =>
-            address == null ? null :
-            !address.Contains("://") ? new Uri("http://" + address) :
-            new Uri(address);
+        private static Uri? CreateProxyUri(string? address, int? port = null)
+        {
+            if (address is null)
+            {
+                return null;
+            }
+
+            if (!address.Contains("://", StringComparison.Ordinal))
+            {
+                address = "http://" + address;
+            }
+
+            var proxyUri = new Uri(address);
+
+            if (port.HasValue && proxyUri.IsAbsoluteUri)
+            {
+                proxyUri = new UriBuilder(proxyUri) { Port = port.Value }.Uri;
+            }
+
+            return proxyUri;
+        }
 
         private void UpdateRegexList(bool canThrow)
         {

src/libraries/System.Net.WebProxy/tests/WebProxyTest.cs

@@ -16,7 +16,12 @@ public static IEnumerable<object[]> Ctor_ExpectedPropertyValues_MemberData()
             yield return new object[] { new WebProxy(), null, false, false, Array.Empty<string>(), null };
 
             yield return new object[] { new WebProxy("http://anything"), new Uri("http://anything"), false, false, Array.Empty<string>(), null };
+            yield return new object[] { new WebProxy("http://anything:42"), new Uri("http://anything:42"), false, false, Array.Empty<string>(), null };
+            yield return new object[] { new WebProxy("anything:42"), new Uri("http://anything:42"), false, false, Array.Empty<string>(), null };
             yield return new object[] { new WebProxy("anything", 42), new Uri("http://anything:42"), false, false, Array.Empty<string>(), null };
+            yield return new object[] { new WebProxy("http://anything", 42), new Uri("http://anything:42"), false, false, Array.Empty<string>(), null };
+            yield return new object[] { new WebProxy("http://anything:123", 42), new Uri("http://anything:42"), false, false, Array.Empty<string>(), null };
+            yield return new object[] { new WebProxy("socks5://anything", 42), new Uri("socks5://anything:42"), false, false, Array.Empty<string>(), null };
             yield return new object[] { new WebProxy(new Uri("http://anything")), new Uri("http://anything"), false, false, Array.Empty<string>(), null };
 
             yield return new object[] { new WebProxy("http://anything", true), new Uri("http://anything"), false, true, Array.Empty<string>(), null };