Reduce AOT binary size (#3091)

* Removed reference to DataContractJsonSerializer.
Enable partial trimming of System.Diagnostics and one Hashtable

* Adjusted deserialization after benchmarking

* Removed unused usings

Author: edwardneal

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlConnectionString.cs

@@ -3,7 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
@@ -396,12 +395,12 @@ internal SqlConnectionString(string connectionString) : base(connectionString, G
             if (_networkLibrary != null)
             { // MDAC 83525
                 string networkLibrary = _networkLibrary.Trim().ToLower(CultureInfo.InvariantCulture);
-                Hashtable netlib = NetlibMapping();
+                Dictionary<string, string> netlib = NetlibMapping();
                 if (!netlib.ContainsKey(networkLibrary))
                 {
                     throw ADP.InvalidConnectionOptionValue(KEY.Network_Library);
                 }
-                _networkLibrary = (string)netlib[networkLibrary];
+                _networkLibrary = netlib[networkLibrary];
             }
             else
             {
@@ -1098,14 +1097,14 @@ internal SqlConnectionEncryptOption ConvertValueToSqlConnectionEncrypt()
             }
         }
 
-        static internal Hashtable NetlibMapping()
+        static internal Dictionary<string, string> NetlibMapping()
         {
             const int NetLibCount = 8;
 
-            Hashtable hash = s_netlibMapping;
+            Dictionary<string, string> hash = s_netlibMapping;
             if (hash == null)
             {
-                hash = new Hashtable(NetLibCount)
+                hash = new Dictionary<string, string>(NetLibCount)
                 {
                     { NETLIB.TCPIP, TdsEnums.TCP },
                     { NETLIB.NamedPipes, TdsEnums.NP },
@@ -1147,7 +1146,7 @@ internal static class NETLIB
             internal const string VIA = "dbmsgnet";
         }
 
-        private static Hashtable s_netlibMapping;
+        private static Dictionary<string, string> s_netlibMapping;
 
 #if NETFRAMEWORK
         protected internal override PermissionSet CreatePermissionSet()

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStaticMethods.cs

@@ -139,10 +139,14 @@ internal static int GetCurrentProcessIdForTdsLoginOnly()
                 // Pick up the process Id from the current process instead of randomly generating it.
                 // This would be helpful while tracing application related issues.
                 int processId;
+#if NET
+                processId = Environment.ProcessId;
+#else
                 using (System.Diagnostics.Process p = System.Diagnostics.Process.GetCurrentProcess())
                 {
                     processId = p.Id;
                 }
+#endif
                 System.Threading.Volatile.Write(ref s_currentProcessId, processId);
             }
             return s_currentProcessId;

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/VirtualSecureModeEnclaveProvider.cs

@@ -7,8 +7,8 @@
 using System.Diagnostics;
 using System.IO;
 using System.Net.Http;
-using System.Runtime.Serialization.Json;
 using System.Security.Cryptography.X509Certificates;
+using System.Text.Json;
 using System.Threading;
 
 namespace Microsoft.Data.SqlClient
@@ -72,8 +72,7 @@ protected override byte[] MakeRequest(string url)
 
                     using (Stream stream = s_client.GetStreamAsync(url).ConfigureAwait(false).GetAwaiter().GetResult())
                     {
-                        var deserializer = new DataContractJsonSerializer(typeof(byte[]));
-                        return (byte[])deserializer.ReadObject(stream);
+                        return JsonSerializer.Deserialize<List<byte>>(stream)?.ToArray();
                     }
                 }
                 catch (Exception e)

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/VirtualSecureModeEnclaveProviderBase.cs

@@ -202,7 +202,7 @@ private X509Certificate2Collection GetSigningCertificate(string attestationUrl,
 
                 try
                 {
-                    var s = new SignedCms();
+                    SignedCms s = new SignedCms();
                     s.Decode(data);
                     certificateCollection.AddRange(s.Certificates);
                 }