Fix ArgumentOutOfRangeException when header value is empty

Tests/HttpUnitTests/WebHeaderCollectionTests.cs

@@ -0,0 +1,55 @@
+//
+// Copyright (c) .NET Foundation and Contributors
+// See LICENSE file in the project root for full license information.
+//
+
+using nanoFramework.TestFramework;
+using System.Net;
+
+namespace HttpUnitTests
+{
+    [TestClass]
+    public class WebHeaderCollectionTests
+    {
+        [TestMethod]
+        public void Add_Authorization_BearerWithSpaceAndNoValue_ShouldNotThrow()
+        {
+            var headers = new WebHeaderCollection();
+            headers.Add("Authorization: Bearer ");
+        }
+
+        [TestMethod]
+        public void Add_Authorization_NoSpaceSingleChar_ShouldNotThrow()
+        {
+            var headers = new WebHeaderCollection();
+            headers.Add("Authorization: 1");
+        }
+
+        [TestMethod]
+        public void Add_Authorization_ValidBearer_ShouldSucceed()
+        {
+            var headers = new WebHeaderCollection();
+            headers.Add("Authorization: Bearer a11111");
+            string value = headers["Authorization"];
+            Assert.AreEqual("Bearer a11111", value);
+        }
+
+        [TestMethod]
+        public void Add_Authorization_ValidTestValue_ShouldSucceed()
+        {
+            var headers = new WebHeaderCollection();
+            headers.Add("Authorization: test 1");
+            string value = headers["Authorization"];
+            Assert.AreEqual("test 1", value);
+        }
+
+        [TestMethod]
+        public void Add_Authorization_ValidSingleLetterPair_ShouldSucceed()
+        {
+            var headers = new WebHeaderCollection();
+            headers.Add("Authorization: a b");
+            string value = headers["Authorization"];
+            Assert.AreEqual("a b", value);
+        }
+    }
+}

nanoFramework.System.Net.Http/Http/System.Net.WebHeaders.cs

@@ -427,7 +427,16 @@ public void Add(string header)
             }
 
             string name = header.Substring(0, colpos);
-            string value = header.Substring(colpos + 1);
+            // Handle empty header value
+            string value;
+            if (colpos + 1 >= header.Length)
+            {
+                value = string.Empty;
+            }
+            else
+            {
+                value = header.Substring(colpos + 1);
+            }
 
             name = CheckBadChars(name, false);
             ThrowOnRestrictedHeader(name);