remove more duplicate lookups (dotnet#4089)

* remove duplicate lookups in EnclaveDelegate.Crypto.cs

* Use TryGet methods to avoid double lookups

Replace ContainsKey + indexer patterns with TryGetParsetableValue (for connection options) and TryGetValue (for _appDomainKeyHash) to avoid double dictionary lookups, remove variable shadowing, and make intent clearer. Existing logic and assertions are preserved.

Author: SimonCropp

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/SqlConnectionPoolGroupProviderInfo.cs

@@ -105,8 +105,8 @@ private PermissionSet CreateFailoverPermission(SqlConnectionString userConnectio
             //       the server, we will use that name over what was specified  
             //       in the original connection string.
 
-            if (userConnectionOptions.ContainsKey(DbConnectionStringKeywords.FailoverPartner) &&
-                userConnectionOptions[DbConnectionStringKeywords.FailoverPartner] == null)
+            if (userConnectionOptions.TryGetParsetableValue(DbConnectionStringKeywords.FailoverPartner, out string failoverPartnerValue) &&
+                failoverPartnerValue == null)
             {
                 keywordToReplace = DbConnectionStringKeywords.DataSource;
             }

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/EnclaveDelegate.Crypto.cs

@@ -92,21 +92,18 @@ private SqlColumnEncryptionEnclaveProvider GetEnclaveProvider(SqlConnectionAttes
                 switch (attestationProtocol)
                 {
                     case SqlConnectionAttestationProtocol.AAS:
-                        AzureAttestationEnclaveProvider azureAttestationEnclaveProvider = new AzureAttestationEnclaveProvider();
-                        s_enclaveProviders[attestationProtocol] = azureAttestationEnclaveProvider;
-                        sqlColumnEncryptionEnclaveProvider = s_enclaveProviders[attestationProtocol];
+                        sqlColumnEncryptionEnclaveProvider = new AzureAttestationEnclaveProvider();
+                        s_enclaveProviders[attestationProtocol] = sqlColumnEncryptionEnclaveProvider;
                         break;
 
                     case SqlConnectionAttestationProtocol.HGS:
-                        HostGuardianServiceEnclaveProvider hostGuardianServiceEnclaveProvider = new HostGuardianServiceEnclaveProvider();
-                        s_enclaveProviders[attestationProtocol] = hostGuardianServiceEnclaveProvider;
-                        sqlColumnEncryptionEnclaveProvider = s_enclaveProviders[attestationProtocol];
+                        sqlColumnEncryptionEnclaveProvider = new HostGuardianServiceEnclaveProvider();
+                        s_enclaveProviders[attestationProtocol] = sqlColumnEncryptionEnclaveProvider;
                         break;
 
                     case SqlConnectionAttestationProtocol.None:
-                        NoneAttestationEnclaveProvider noneAttestationEnclaveProvider = new NoneAttestationEnclaveProvider();
-                        s_enclaveProviders[attestationProtocol] = noneAttestationEnclaveProvider;
-                        sqlColumnEncryptionEnclaveProvider = s_enclaveProviders[attestationProtocol];
+                        sqlColumnEncryptionEnclaveProvider = new NoneAttestationEnclaveProvider();
+                        s_enclaveProviders[attestationProtocol] = sqlColumnEncryptionEnclaveProvider;
                         break;
 
                     default:

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlDependencyListener.cs

@@ -837,9 +837,8 @@ internal bool Stop(string appDomainKey, out bool appDomainStop)
                     // If null, then this was called from SqlDependencyProcessDispatcher, we ignore appDomainKeyHash.
                     lock (_appDomainKeyHash)
                     {
-                        if (_appDomainKeyHash.ContainsKey(appDomainKey))
+                        if (_appDomainKeyHash.TryGetValue(appDomainKey, out int value))
                         { // Do nothing if AppDomain did not call Start!
-                            int value = _appDomainKeyHash[appDomainKey];
 
                             Debug.Assert(value > 0, "Unexpected count for appDomainKey");
                             SqlClientEventSource.Log.TryNotificationTraceEvent("<sc.SqlConnectionContainer.Stop|DEP> _appDomainKeyHash contained AppDomainKey: '{0}', pre-decrement Count: '{1}'.", appDomainKey, value);