Add span-based Uri {Try}{Un}EscapeDataString overloads

src/libraries/System.Net.Http/src/System/Net/Http/FormUrlEncodedContent.cs

@@ -28,30 +28,61 @@ private static byte[] GetContentByteArray(IEnumerable<KeyValuePair<string?, stri
             ArgumentNullException.ThrowIfNull(nameValueCollection);
 
             // Encode and concatenate data
-            StringBuilder builder = new StringBuilder();
+            var builder = new ValueStringBuilder(stackalloc char[256]);
+
             foreach (KeyValuePair<string?, string?> pair in nameValueCollection)
             {
                 if (builder.Length > 0)
                 {
                     builder.Append('&');
                 }
 
-                builder.Append(Encode(pair.Key));
+                Encode(ref builder, pair.Key);
                 builder.Append('=');
-                builder.Append(Encode(pair.Value));
+                Encode(ref builder, pair.Value);
             }
 
-            return HttpRuleParser.DefaultHttpEncoding.GetBytes(builder.ToString());
+            // We know the encoded length because the input is all ASCII.
+            byte[] bytes = new byte[builder.Length];
+            HttpRuleParser.DefaultHttpEncoding.GetBytes(builder.AsSpan(), bytes);
+            builder.Dispose();
+            return bytes;
         }
 
-        private static string Encode(string? data)
+        private static void Encode(ref ValueStringBuilder builder, string? data)
         {
-            if (string.IsNullOrEmpty(data))
+            if (!string.IsNullOrEmpty(data))
             {
-                return string.Empty;
+                int charsWritten;
+                while (!Uri.TryEscapeDataString(data, builder.RawChars.Slice(builder.Length), out charsWritten))
+                {
+                    builder.EnsureCapacity(builder.Capacity + 1);
+                }
+
+                // Escape spaces as '+'.
+                if (data.Contains(' '))
+                {
+                    ReadOnlySpan<char> escapedChars = builder.RawChars.Slice(builder.Length, charsWritten);
+
+                    while (true)
+                    {
+                        int indexOfEscapedSpace = escapedChars.IndexOf("%20", StringComparison.Ordinal);
+                        if (indexOfEscapedSpace < 0)
+                        {
+                            builder.Append(escapedChars);
+                            break;
+                        }
+
+                        builder.Append(escapedChars.Slice(0, indexOfEscapedSpace));
+                        builder.Append('+');
+                        escapedChars = escapedChars.Slice(indexOfEscapedSpace + 3); // Skip "%20"
+                    }
+                }
+                else
+                {
+                    builder.Length += charsWritten;
+                }
             }
-            // Escape spaces as '+'.
-            return Uri.EscapeDataString(data).Replace("%20", "+");
         }
 
         protected override Task SerializeToStreamAsync(Stream stream, TransportContext? context, CancellationToken cancellationToken) =>

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpEnvironmentProxy.cs

@@ -170,16 +170,9 @@ private HttpEnvironmentProxy(Uri? httpProxy, Uri? httpsProxy, string? bypassList
             int separatorIndex = value.LastIndexOf('@');
             if (separatorIndex != -1)
             {
-                string auth = value.Substring(0, separatorIndex);
-
                 // The User and password may or may not be URL encoded.
-                // Curl seems to accept both. To match that,
-                // we do opportunistic decode and we use original string if it fails.
-                try
-                {
-                    auth = Uri.UnescapeDataString(auth);
-                }
-                catch { };
+                // Curl seems to accept both. To match that, we also decode the value.
+                string auth = Uri.UnescapeDataString(value.AsSpan(0, separatorIndex));
 
                 value = value.Substring(separatorIndex + 1);
                 separatorIndex = auth.IndexOf(':');

src/libraries/System.Net.Requests/src/System/Net/FtpWebRequest.cs

@@ -495,17 +495,17 @@ internal FtpWebRequest(Uri uri)
             NetworkCredential? networkCredential = null;
             _uri = uri;
             _methodInfo = FtpMethodInfo.GetMethodInfo(WebRequestMethods.Ftp.DownloadFile);
-            if (!string.IsNullOrEmpty(_uri.UserInfo))
+
+            if (_uri.UserInfo is { Length: > 0 } userInfo)
             {
-                string userInfo = _uri.UserInfo;
                 string username = userInfo;
                 string password = "";
                 int index = userInfo.IndexOf(':');
                 if (index != -1)
                 {
-                    username = Uri.UnescapeDataString(userInfo.Substring(0, index));
+                    username = Uri.UnescapeDataString(userInfo.AsSpan(0, index));
                     index++; // skip ':'
-                    password = Uri.UnescapeDataString(userInfo.Substring(index));
+                    password = Uri.UnescapeDataString(userInfo.AsSpan(index));
                 }
                 networkCredential = new NetworkCredential(username, password);
             }