Enable Form and Query access off of requests

src/SystemWebAdapters/src/HttpRequest.cs

@@ -24,8 +24,10 @@ public class HttpRequest
 
         private RequestHeaders? _typedHeaders;
         private string[]? _userLanguages;
-        private StringValuesNameValueCollection? _headers;
-        private ServerVariablesNameValueCollection? _serverVariables;
+        private NameValueCollection? _headers;
+        private NameValueCollection? _serverVariables;
+        private NameValueCollection? _form;
+        private NameValueCollection? _query;
 
         public HttpRequest(HttpRequestCore request)
         {
@@ -34,7 +36,7 @@ public HttpRequest(HttpRequestCore request)
 
         public string? Path => _request.Path.Value;
 
-        public NameValueCollection Headers => _headers ??= new(_request.Headers);
+        public NameValueCollection Headers => _headers ??= _request.Headers.ToNameValueCollection();
 
         public Uri Url => new(_request.GetEncodedUrl());
 
@@ -85,7 +87,7 @@ public string[] UserLanguages
 
         public string RequestType => HttpMethod;
 
-        public NameValueCollection Form => throw new NotImplementedException();
+        public NameValueCollection Form => _form ??= _request.Form.ToNameValueCollection();
 
         public HttpCookieCollection Cookies => throw new NotImplementedException();
 
@@ -109,7 +111,7 @@ public NameValueCollection ServerVariables
                 {
                     if (_request.HttpContext.Features.Get<IServerVariablesFeature>() is IServerVariablesFeature feature)
                     {
-                        _serverVariables = new(feature);
+                        _serverVariables = feature.ToNameValueCollection();
                     }
                     else
                     {
@@ -123,7 +125,7 @@ public NameValueCollection ServerVariables
 
         public bool IsSecureConnection => _request.IsHttps;
 
-        public NameValueCollection QueryString => throw new NotImplementedException();
+        public NameValueCollection QueryString => _query ??= _request.Query.ToNameValueCollection();
 
         public bool IsLocal
         {

src/SystemWebAdapters/src/HttpResponse.cs

@@ -32,19 +32,8 @@ public string StatusDescription
             set => throw new NotImplementedException();
         }
 
-        public NameValueCollection Headers
-        {
-            get
-            {
-                if (_headers is null)
-                {
-                    _headers = new StringValuesNameValueCollection(_response.Headers);
-                }
-
-                return _headers;
-            }
-        }
-
+        public NameValueCollection Headers => _headers ??= _response.Headers.ToNameValueCollection();
+
         public bool TrySkipIisCustomErrors
         {
             get => throw new NotImplementedException();

src/SystemWebAdapters/src/Internal/FormCollectionReadOnlyDictionary.cs

@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Primitives;
+
+namespace System.Web.Internal;
+
+internal class FormCollectionReadOnlyDictionary : IReadOnlyDictionary<string, StringValues>
+{
+    private readonly IFormCollection _form;
+
+    public FormCollectionReadOnlyDictionary(IFormCollection form)
+    {
+        _form = form;
+    }
+
+    public StringValues this[string key] => _form[key];
+
+    public IEnumerable<string> Keys => _form.Keys;
+
+    public IEnumerable<StringValues> Values
+    {
+        get
+        {
+            foreach (var item in _form)
+            {
+                yield return item.Value;
+            }
+        }
+    }
+
+    public int Count => _form.Count;
+
+    public bool ContainsKey(string key) => _form.ContainsKey(key);
+
+    public IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator() => _form.GetEnumerator();
+
+    public bool TryGetValue(string key, [MaybeNullWhen(false)] out StringValues value) => _form.TryGetValue(key, out value);
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+}

src/SystemWebAdapters/src/Internal/NameValueCollectionExtensions.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Features;
+using Microsoft.Extensions.Primitives;
+
+namespace System.Web.Internal;
+
+internal static class NameValueCollectionExtensions
+{
+    public static NameValueCollection ToNameValueCollection(this IQueryCollection query)
+    {
+        if (query.Count == 0)
+        {
+            return StringValuesReadOnlyDictionaryNameValueCollection.Empty;
+        }
+
+        return new StringValuesReadOnlyDictionaryNameValueCollection(new QueryCollectionReadOnlyDictionary(query));
+    }
+
+    public static NameValueCollection ToNameValueCollection(this IFormCollection form)
+    {
+        if (form.Count == 0)
+        {
+            return StringValuesReadOnlyDictionaryNameValueCollection.Empty;
+        }
+
+        return new StringValuesReadOnlyDictionaryNameValueCollection(new FormCollectionReadOnlyDictionary(form));
+    }
+
+    public static NameValueCollection ToNameValueCollection(this IHeaderDictionary headers) => new StringValuesDictionaryNameValueCollection(headers);
+
+    public static NameValueCollection ToNameValueCollection(this IServerVariablesFeature serverVariables) => new ServerVariablesNameValueCollection(serverVariables);
+}

src/SystemWebAdapters/src/Internal/QueryCollectionReadOnlyDictionary.cs

@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Primitives;
+
+namespace System.Web.Internal;
+
+internal class QueryCollectionReadOnlyDictionary : IReadOnlyDictionary<string, StringValues>
+{
+    private readonly IQueryCollection _query;
+
+    public QueryCollectionReadOnlyDictionary(IQueryCollection query)
+    {
+        _query = query;
+    }
+
+    public StringValues this[string key] => _query[key];
+
+    public IEnumerable<string> Keys => _query.Keys;
+
+    public IEnumerable<StringValues> Values
+    {
+        get
+        {
+            foreach (var item in _query)
+            {
+                yield return item.Value;
+            }
+        }
+    }
+
+    public int Count => _query.Count;
+
+    public bool ContainsKey(string key) => _query.ContainsKey(key);
+
+    public IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator() => _query.GetEnumerator();
+
+    public bool TryGetValue(string key, [MaybeNullWhen(false)] out StringValues value) => _query.TryGetValue(key, out value);
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+}

src/SystemWebAdapters/src/Internal/ServerVariablesNameValueCollection.cs

@@ -1,14 +1,13 @@
-using System.Collections;
+using System.Collections;
 using System.Collections.Specialized;
 using System.Runtime.Serialization;
 using Microsoft.AspNetCore.Http.Features;
 
 namespace System.Web.Internal
 {
-    internal class ServerVariablesNameValueCollection : NameValueCollection
+    internal class ServerVariablesNameValueCollection : WrappingNameValueCollection
     {
         private const string EnumerationErrorMessage = "ASP.NET Core doesn't support enumerating server variables.";
-        private const string IndexErrorMessage = "ASP.NET Core doesn't support accessing server variables by index.";
         private const string SerializationErrorMessage = "ASP.NET Core doesn't suppor serialization of server variables.";
 
         private readonly IServerVariablesFeature _serverVariables;
@@ -33,14 +32,6 @@ public override void Add(string? name, string? value)
             _serverVariables[name] = value;
         }
 
-        public override KeysCollection Keys => throw new PlatformNotSupportedException("KeysCollection is not supported as Get(int) is not available.");
-
-        public override string? Get(int index) => throw new PlatformNotSupportedException(IndexErrorMessage);
-
-        public override string? GetKey(int index) => throw new PlatformNotSupportedException(IndexErrorMessage);
-
-        public override string[]? GetValues(int index) => throw new PlatformNotSupportedException(IndexErrorMessage);
-
         public override string[]? GetValues(string? name)
         {
             if (name is not null && _serverVariables[name] is string result)
@@ -87,6 +78,6 @@ public override void Set(string? name, string? value)
 
         public override void GetObjectData(SerializationInfo info, StreamingContext context) => throw new PlatformNotSupportedException(SerializationErrorMessage);
 
-        public override void OnDeserialization(object? sender)=> throw new PlatformNotSupportedException(SerializationErrorMessage);
+        public override void OnDeserialization(object? sender) => throw new PlatformNotSupportedException(SerializationErrorMessage);
     }
 }

src/SystemWebAdapters/src/Internal/StringValuesDictionaryNameValueCollection.cs

@@ -0,0 +1,66 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Extensions.Primitives;
+
+namespace System.Web.Internal
+{
+    internal class StringValuesDictionaryNameValueCollection : WrappingNameValueCollection
+    {
+        private readonly IDictionary<string, StringValues> _values;
+
+        public StringValuesDictionaryNameValueCollection(IDictionary<string, StringValues> headers)
+        {
+            _values = headers;
+        }
+
+        public override string?[] AllKeys => _values.Keys.ToArray();
+
+        public override int Count => _values.Count;
+
+        public override void Add(string? name, string? value)
+        {
+            if (name is null)
+            {
+                return;
+            }
+
+            if (_values.TryGetValue(name, out var existing))
+            {
+                _values[name] = StringValues.Concat(existing, value);
+            }
+            else
+            {
+                _values.Add(name, value);
+            }
+        }
+
+        public override string[]? GetValues(string? name)
+            => name is not null && _values.TryGetValue(name, out var values) ? values : default;
+
+        public override void Remove(string? name)
+        {
+            if (name is not null)
+            {
+                _values.Remove(name);
+            }
+        }
+
+        public override void Set(string? name, string? value)
+        {
+            if (name is null)
+            {
+                return;
+            }
+
+            _values[name] = value;
+        }
+
+        public override string? Get(string? name)
+            => name is not null && _values.TryGetValue(name, out var values) ? values : default;
+
+        public override void Clear() => _values.Clear();
+
+        public override IEnumerator GetEnumerator() => _values.Keys.GetEnumerator();
+    }
+}