Fix HttpHeaders.Remove to handle well-known header names

src/libraries/System.Net.Http/src/System/Net/Http/Headers/HttpHeaders.cs

@@ -309,7 +309,9 @@ internal bool TryGetValues(HeaderDescriptor descriptor, [NotNullWhen(true)] out
             return false;
         }
 
-        public bool Contains(string name) => Contains(GetHeaderDescriptor(name));
+        public bool Contains(string name) =>
+            TryGetHeaderDescriptor(name, out HeaderDescriptor descriptor) &&
+            Contains(descriptor);
 
         public override string ToString()
         {
@@ -478,7 +480,9 @@ internal void SetOrRemoveParsedValue(HeaderDescriptor descriptor, object? value)
             }
         }
 
-        public bool Remove(string name) => Remove(GetHeaderDescriptor(name));
+        public bool Remove(string name) =>
+            TryGetHeaderDescriptor(name, out HeaderDescriptor descriptor) &&
+            Remove(descriptor);
 
         internal bool RemoveParsedValue(HeaderDescriptor descriptor, object value, bool removeAll = false)
         {

src/libraries/System.Net.Http/tests/UnitTests/Headers/HttpContentHeadersTest.cs

@@ -498,6 +498,26 @@ public void InvalidHeaders_AddRequestAndResponseHeaders_Throw()
             Assert.Throws<InvalidOperationException>(() => { _headers.Add("Warning", "v"); });
         }
 
+        [Fact]
+        public void Contains_DisallowedRequestHeaderOnContentHeaders_ReturnsFalse()
+        {
+            using var content = new StringContent("test");
+            HttpContentHeaders headers = content.Headers;
+            Assert.False(headers.Contains("Accept"));
+            Assert.False(headers.Contains("Accept-Encoding"));
+            Assert.False(headers.Contains("Host"));
+        }
+
+        [Fact]
+        public void Remove_DisallowedRequestHeaderOnContentHeaders_ReturnsFalse()
+        {
+            using var content = new StringContent("test");
+            HttpContentHeaders headers = content.Headers;
+            Assert.False(headers.Remove("Accept"));
+            Assert.False(headers.Remove("Accept-Encoding"));
+            Assert.False(headers.Remove("Host"));
+        }
+
         private sealed class ComputeLengthHttpContent : HttpContent
         {
             private readonly Func<long?> _tryComputeLength;

src/libraries/System.Net.Http/tests/UnitTests/Headers/HttpHeadersTest.cs

@@ -1069,29 +1069,21 @@ public void Clear_AddMultipleHeadersAndThenClear_NoHeadersInCollection()
             Assert.Equal(2, headers.Parser.TryParseValueCallCount);
         }
 
-        [Fact]
-        public void Remove_UseNullHeaderName_Throw()
-        {
-            MockHeaders headers = new MockHeaders();
-
-            AssertExtensions.Throws<ArgumentNullException>("name", () => { headers.Remove(null); });
-        }
-
-        [Fact]
-        public void Remove_UseEmptyHeaderName_Throw()
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        public void Remove_UseNullOrEmptyHeaderName_ReturnsFalse(string? headerName)
         {
             MockHeaders headers = new MockHeaders();
-
-            AssertExtensions.Throws<ArgumentException>("name", () => { headers.Remove(""); });
+            Assert.False(headers.Remove(headerName));
         }
 
         [Theory]
         [MemberData(nameof(GetInvalidHeaderNames))]
-        public void Remove_UseInvalidHeaderName_Throw(string headerName)
+        public void Remove_UseInvalidHeaderName_ReturnsFalse(string headerName)
         {
             MockHeaders headers = new MockHeaders();
-
-            Assert.Throws<FormatException>(() => { headers.Remove(headerName); });
+            Assert.False(headers.Remove(headerName));
         }
 
         [Fact]
@@ -1593,29 +1585,21 @@ public void NonValidated_ValidInvalidAndRaw_AllReturned()
             }
         }
 
-        [Fact]
-        public void Contains_UseNullHeaderName_Throw()
-        {
-            MockHeaders headers = new MockHeaders();
-
-            AssertExtensions.Throws<ArgumentNullException>("name", () => { headers.Contains(null); });
-        }
-
-        [Fact]
-        public void Contains_UseEmptyHeaderName_Throw()
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        public void Contains_UseNullOrEmptyHeaderName_ReturnsFalse(string? headerName)
         {
             MockHeaders headers = new MockHeaders();
-
-            AssertExtensions.Throws<ArgumentException>("name", () => { headers.Contains(""); });
+            Assert.False(headers.Contains(headerName));
         }
 
         [Theory]
         [MemberData(nameof(GetInvalidHeaderNames))]
-        public void Contains_UseInvalidHeaderName_Throw(string headerName)
+        public void Contains_UseInvalidHeaderName_ReturnsFalse(string headerName)
         {
             MockHeaders headers = new MockHeaders();
-
-            Assert.Throws<FormatException>(() => { headers.Contains(headerName); });
+            Assert.False(headers.Contains(headerName));
         }
 
         [Fact]
@@ -2549,10 +2533,10 @@ public async Task ConcurrentReads_ReturnTheSameParsedValues(bool useDictionary,
         }
 
         [Fact]
-        public void TryAddInvalidHeader_ShouldThrowFormatException()
+        public void Remove_InvalidHeaderName_ReturnsFalse()
         {
             MockHeaders headers = new MockHeaders();
-            AssertExtensions.ThrowsContains<FormatException>(() => headers.Remove("\u0080"), "\u0080");
+            Assert.False(headers.Remove("\u0080"));
         }
 
         [Theory]

src/libraries/System.Net.Http/tests/UnitTests/Headers/HttpRequestHeadersTest.cs

@@ -1650,5 +1650,23 @@ public void InvalidHeaders_AddContentHeaders_Throw()
             Assert.Throws<InvalidOperationException>(() => { headers.Add("Expires", "v"); });
             Assert.Throws<InvalidOperationException>(() => { headers.Add("Last-Modified", "v"); });
         }
+
+        [Fact]
+        public void Contains_DisallowedContentHeaderOnRequestHeaders_ReturnsFalse()
+        {
+            HttpRequestHeaders headers = new HttpRequestMessage().Headers;
+            Assert.False(headers.Contains("Content-Type"));
+            Assert.False(headers.Contains("Content-Encoding"));
+            Assert.False(headers.Contains("content-length"));
+        }
+
+        [Fact]
+        public void Remove_DisallowedContentHeaderOnRequestHeaders_ReturnsFalse()
+        {
+            HttpRequestHeaders headers = new HttpRequestMessage().Headers;
+            Assert.False(headers.Remove("Content-Type"));
+            Assert.False(headers.Remove("Content-Encoding"));
+            Assert.False(headers.Remove("content-length"));
+        }
     }
 }

src/libraries/System.Net.Http/tests/UnitTests/Headers/HttpResponseHeadersTest.cs

@@ -710,5 +710,21 @@ public void InvalidHeaders_AddContentHeaders_Throw()
             Assert.Throws<InvalidOperationException>(() => { headers.Add("Expires", "v"); });
             Assert.Throws<InvalidOperationException>(() => { headers.Add("Last-Modified", "v"); });
         }
+
+        [Fact]
+        public void Contains_DisallowedContentHeaderOnResponseHeaders_ReturnsFalse()
+        {
+            Assert.False(headers.Contains("Content-Type"));
+            Assert.False(headers.Contains("Content-Encoding"));
+            Assert.False(headers.Contains("content-length"));
+        }
+
+        [Fact]
+        public void Remove_DisallowedContentHeaderOnResponseHeaders_ReturnsFalse()
+        {
+            Assert.False(headers.Remove("Content-Type"));
+            Assert.False(headers.Remove("Content-Encoding"));
+            Assert.False(headers.Remove("content-length"));
+        }
     }
-}
+}