Refactoring in Asn1 classes

28 files changed, 117 insertions, 145 deletions

diff --git a/crypto/src/asn1/cms/AuthEnvelopedData.cs b/crypto/src/asn1/cms/AuthEnvelopedData.cs
index 4ca86e9df..8f980e6ec 100644
--- a/crypto/src/asn1/cms/AuthEnvelopedData.cs
+++ b/crypto/src/asn1/cms/AuthEnvelopedData.cs
@@ -49,8 +49,7 @@ namespace Org.BouncyCastle.Asn1.Cms
 			this.unauthAttrs = unauthAttrs;
 	    }
 
-		private AuthEnvelopedData(
-			Asn1Sequence	seq)
+		private AuthEnvelopedData(Asn1Sequence seq)
 		{
 			int index = 0;
 
@@ -61,9 +60,9 @@ namespace Org.BouncyCastle.Asn1.Cms
 				throw new ArgumentException("AuthEnvelopedData version number must be 0");
 
 			tmp = seq[index++].ToAsn1Object();
-			if (tmp is Asn1TaggedObject)
+			if (tmp is Asn1TaggedObject taggedObject1)
 			{
-				originatorInfo = OriginatorInfo.GetInstance((Asn1TaggedObject)tmp, false);
+				originatorInfo = OriginatorInfo.GetInstance(taggedObject1, false);
 				tmp = seq[index++].ToAsn1Object();
 			}
 
@@ -76,9 +75,9 @@ namespace Org.BouncyCastle.Asn1.Cms
 			authEncryptedContentInfo = EncryptedContentInfo.GetInstance(tmp);
 
 			tmp = seq[index++].ToAsn1Object();
-			if (tmp is Asn1TaggedObject)
+			if (tmp is Asn1TaggedObject taggedObject2)
 			{
-				authAttrs = Asn1Set.GetInstance((Asn1TaggedObject)tmp, false);
+				authAttrs = Asn1Set.GetInstance(taggedObject2, false);
 				tmp = seq[index++].ToAsn1Object();
 			}
 			else
diff --git a/crypto/src/asn1/cms/AuthenticatedData.cs b/crypto/src/asn1/cms/AuthenticatedData.cs
index eb9f82031..6ec8061e2 100644
--- a/crypto/src/asn1/cms/AuthenticatedData.cs
+++ b/crypto/src/asn1/cms/AuthenticatedData.cs
@@ -48,17 +48,16 @@ namespace Org.BouncyCastle.Asn1.Cms
 			this.unauthAttrs = unauthAttrs;
 		}
 
-		private AuthenticatedData(
-			Asn1Sequence	seq)
+		private AuthenticatedData(Asn1Sequence seq)
 		{
 			int index = 0;
 
 			version = (DerInteger)seq[index++];
 
 			Asn1Encodable tmp = seq[index++];
-			if (tmp is Asn1TaggedObject)
+			if (tmp is Asn1TaggedObject taggedObject1)
 			{
-				originatorInfo = OriginatorInfo.GetInstance((Asn1TaggedObject)tmp, false);
+				originatorInfo = OriginatorInfo.GetInstance(taggedObject1, false);
 				tmp = seq[index++];
 			}
 
@@ -66,18 +65,18 @@ namespace Org.BouncyCastle.Asn1.Cms
 			macAlgorithm = AlgorithmIdentifier.GetInstance(seq[index++]);
 
 			tmp = seq[index++];
-			if (tmp is Asn1TaggedObject)
+			if (tmp is Asn1TaggedObject taggedObject2)
 			{
-				digestAlgorithm = AlgorithmIdentifier.GetInstance((Asn1TaggedObject)tmp, false);
+				digestAlgorithm = AlgorithmIdentifier.GetInstance(taggedObject2, false);
 				tmp = seq[index++];
 			}
 
 			encapsulatedContentInfo = ContentInfo.GetInstance(tmp);
 
 			tmp = seq[index++];
-			if (tmp is Asn1TaggedObject)
+			if (tmp is Asn1TaggedObject taggedObject3)
 			{
-				authAttrs = Asn1Set.GetInstance((Asn1TaggedObject)tmp, false);
+				authAttrs = Asn1Set.GetInstance(taggedObject3, false);
 				tmp = seq[index++];
 			}
 
diff --git a/crypto/src/asn1/cms/EnvelopedData.cs b/crypto/src/asn1/cms/EnvelopedData.cs
index 45e9c5c76..85216a2e8 100644
--- a/crypto/src/asn1/cms/EnvelopedData.cs
+++ b/crypto/src/asn1/cms/EnvelopedData.cs
@@ -45,9 +45,9 @@ namespace Org.BouncyCastle.Asn1.Cms
 
             object tmp = seq[index++];
 
-            if (tmp is Asn1TaggedObject)
+            if (tmp is Asn1TaggedObject taggedObject)
             {
-                originatorInfo = OriginatorInfo.GetInstance((Asn1TaggedObject) tmp, false);
+                originatorInfo = OriginatorInfo.GetInstance(taggedObject, false);
                 tmp = seq[index++];
             }
 
@@ -56,7 +56,7 @@ namespace Org.BouncyCastle.Asn1.Cms
 
             if (seq.Count > index)
             {
-                unprotectedAttrs = Asn1Set.GetInstance((Asn1TaggedObject) seq[index], false);
+                unprotectedAttrs = Asn1Set.GetInstance((Asn1TaggedObject)seq[index], false);
             }
         }
 
diff --git a/crypto/src/asn1/cms/KeyAgreeRecipientInfo.cs b/crypto/src/asn1/cms/KeyAgreeRecipientInfo.cs
index 52eb7d4d3..be2d76e2c 100644
--- a/crypto/src/asn1/cms/KeyAgreeRecipientInfo.cs
+++ b/crypto/src/asn1/cms/KeyAgreeRecipientInfo.cs
@@ -27,25 +27,22 @@ namespace Org.BouncyCastle.Asn1.Cms
             this.recipientEncryptedKeys = recipientEncryptedKeys;
         }
 
-		public KeyAgreeRecipientInfo(
-            Asn1Sequence seq)
+		public KeyAgreeRecipientInfo(Asn1Sequence seq)
         {
             int index = 0;
 
             version = (DerInteger) seq[index++];
-            originator = OriginatorIdentifierOrKey.GetInstance(
-				(Asn1TaggedObject) seq[index++], true);
+            originator = OriginatorIdentifierOrKey.GetInstance((Asn1TaggedObject)seq[index++], true);
 
-			if (seq[index] is Asn1TaggedObject)
+			if (seq[index] is Asn1TaggedObject taggedObject)
             {
-                ukm = Asn1OctetString.GetInstance(
-					(Asn1TaggedObject) seq[index++], true);
+                ukm = Asn1OctetString.GetInstance(taggedObject, true);
+                ++index;
             }
 
-			keyEncryptionAlgorithm = AlgorithmIdentifier.GetInstance(
-				seq[index++]);
+			keyEncryptionAlgorithm = AlgorithmIdentifier.GetInstance(seq[index++]);
 
-			recipientEncryptedKeys = (Asn1Sequence) seq[index++];
+			recipientEncryptedKeys = (Asn1Sequence)seq[index++];
         }
 
 		/**
diff --git a/crypto/src/asn1/cms/MetaData.cs b/crypto/src/asn1/cms/MetaData.cs
index ad2b5c426..6435d4d2e 100644
--- a/crypto/src/asn1/cms/MetaData.cs
+++ b/crypto/src/asn1/cms/MetaData.cs
@@ -28,15 +28,17 @@ namespace Org.BouncyCastle.Asn1.Cms
 
 			int index = 1;
 
-			if (index < seq.Count && seq[index] is DerUtf8String)
+			if (index < seq.Count && seq[index] is DerUtf8String utf8)
 			{
-				this.fileName = DerUtf8String.GetInstance(seq[index++]);
+				this.fileName = utf8;
+				++index;
 			}
-			if (index < seq.Count && seq[index] is DerIA5String)
+			if (index < seq.Count && seq[index] is DerIA5String ia5)
 			{
-				this.mediaType = DerIA5String.GetInstance(seq[index++]);
-			}
-			if (index < seq.Count)
+				this.mediaType = ia5;
+                ++index;
+            }
+            if (index < seq.Count)
 			{
 				this.otherMetaData = Attributes.GetInstance(seq[index++]);
 			}
diff --git a/crypto/src/asn1/cms/PasswordRecipientInfo.cs b/crypto/src/asn1/cms/PasswordRecipientInfo.cs
index 596dd9537..9fb639bf3 100644
--- a/crypto/src/asn1/cms/PasswordRecipientInfo.cs
+++ b/crypto/src/asn1/cms/PasswordRecipientInfo.cs
@@ -33,21 +33,20 @@ namespace Org.BouncyCastle.Asn1.Cms
 			this.encryptedKey = encryptedKey;
 		}
 
-		public PasswordRecipientInfo(
-            Asn1Sequence seq)
+		public PasswordRecipientInfo(Asn1Sequence seq)
         {
-            version = (DerInteger) seq[0];
+            version = (DerInteger)seq[0];
 
-			if (seq[1] is Asn1TaggedObject)
+			if (seq[1] is Asn1TaggedObject taggedObject)
             {
-                keyDerivationAlgorithm = AlgorithmIdentifier.GetInstance((Asn1TaggedObject) seq[1], false);
+                keyDerivationAlgorithm = AlgorithmIdentifier.GetInstance(taggedObject, false);
                 keyEncryptionAlgorithm = AlgorithmIdentifier.GetInstance(seq[2]);
-                encryptedKey = (Asn1OctetString) seq[3];
+                encryptedKey = (Asn1OctetString)seq[3];
             }
             else
             {
                 keyEncryptionAlgorithm = AlgorithmIdentifier.GetInstance(seq[1]);
-                encryptedKey = (Asn1OctetString) seq[2];
+                encryptedKey = (Asn1OctetString)seq[2];
             }
         }
 
diff --git a/crypto/src/asn1/cms/RecipientKeyIdentifier.cs b/crypto/src/asn1/cms/RecipientKeyIdentifier.cs
index 512025808..60a6151bf 100644
--- a/crypto/src/asn1/cms/RecipientKeyIdentifier.cs
+++ b/crypto/src/asn1/cms/RecipientKeyIdentifier.cs
@@ -43,24 +43,24 @@ namespace Org.BouncyCastle.Asn1.Cms
 
 			switch(seq.Count)
             {
-				case 1:
-					break;
-				case 2:
-					if (seq[1] is Asn1GeneralizedTime asn1GeneralizedTime)
-					{
-						date = asn1GeneralizedTime;
-					}
-					else
-					{
-						other = OtherKeyAttribute.GetInstance(seq[2]);
-					}
-					break;
-				case 3:
-					date = (Asn1GeneralizedTime)seq[1];
+			case 1:
+				break;
+			case 2:
+				if (seq[1] is Asn1GeneralizedTime asn1GeneralizedTime)
+				{
+					date = asn1GeneralizedTime;
+				}
+				else
+				{
 					other = OtherKeyAttribute.GetInstance(seq[2]);
-					break;
-				default:
-					throw new ArgumentException("Invalid RecipientKeyIdentifier");
+				}
+				break;
+			case 3:
+				date = (Asn1GeneralizedTime)seq[1];
+				other = OtherKeyAttribute.GetInstance(seq[2]);
+				break;
+			default:
+				throw new ArgumentException("Invalid RecipientKeyIdentifier");
             }
         }
 
diff --git a/crypto/src/asn1/cms/SCVPReqRes.cs b/crypto/src/asn1/cms/SCVPReqRes.cs
index 6544c852b..8b5f858a6 100644
--- a/crypto/src/asn1/cms/SCVPReqRes.cs
+++ b/crypto/src/asn1/cms/SCVPReqRes.cs
@@ -19,9 +19,9 @@ namespace Org.BouncyCastle.Asn1.Cms
 
         private ScvpReqRes(Asn1Sequence seq)
         {
-            if (seq[0] is Asn1TaggedObject)
+            if (seq[0] is Asn1TaggedObject taggedObject)
             {
-                this.request = ContentInfo.GetInstance(Asn1TaggedObject.GetInstance(seq[0]), true);
+                this.request = ContentInfo.GetInstance(taggedObject, true);
                 this.response = ContentInfo.GetInstance(seq[1]);
             }
             else
diff --git a/crypto/src/asn1/cms/TimeStampedData.cs b/crypto/src/asn1/cms/TimeStampedData.cs
index 15448a923..f90e5b086 100644
--- a/crypto/src/asn1/cms/TimeStampedData.cs
+++ b/crypto/src/asn1/cms/TimeStampedData.cs
@@ -26,17 +26,19 @@ namespace Org.BouncyCastle.Asn1.Cms
 			this.version = DerInteger.GetInstance(seq[0]);
 			
 			int index = 1;
-			if (seq[index] is DerIA5String)
+			if (seq[index] is DerIA5String ia5)
 			{
-				this.dataUri = DerIA5String.GetInstance(seq[index++]);
+				this.dataUri = ia5;
+				++index;
 			}
 			if (seq[index] is MetaData || seq[index] is Asn1Sequence)
 			{
 				this.metaData = MetaData.GetInstance(seq[index++]);
 			}
-			if (seq[index] is Asn1OctetString)
+			if (seq[index] is Asn1OctetString octets)
 			{
-				this.content = Asn1OctetString.GetInstance(seq[index++]);
+				this.content = octets;
+				++index;
 			}
 			this.temporalEvidence = Evidence.GetInstance(seq[index]);
 		}
diff --git a/crypto/src/asn1/crmf/EncKeyWithID.cs b/crypto/src/asn1/crmf/EncKeyWithID.cs
index 6de56fa0b..67c16605a 100644
--- a/crypto/src/asn1/crmf/EncKeyWithID.cs
+++ b/crypto/src/asn1/crmf/EncKeyWithID.cs
@@ -34,7 +34,7 @@ namespace Org.BouncyCastle.Asn1.Crmf
                 }
                 else
                 {
-                    this.identifier = (Asn1Encodable)seq[1];
+                    this.identifier = seq[1];
                 }
             }
             else
diff --git a/crypto/src/asn1/esf/SignerAttribute.cs b/crypto/src/asn1/esf/SignerAttribute.cs
index f90968cf8..03cdd4ba8 100644
--- a/crypto/src/asn1/esf/SignerAttribute.cs
+++ b/crypto/src/asn1/esf/SignerAttribute.cs
@@ -26,11 +26,10 @@ namespace Org.BouncyCastle.Asn1.Esf
 				"obj");
 		}
 
-		private SignerAttribute(
-			object obj)
+		private SignerAttribute(object obj)
 		{
-			Asn1Sequence seq = (Asn1Sequence) obj;
-			DerTaggedObject taggedObject = (DerTaggedObject) seq[0];
+			Asn1Sequence seq = (Asn1Sequence)obj;
+			Asn1TaggedObject taggedObject = (Asn1TaggedObject)seq[0];
 			if (taggedObject.TagNo == 0)
 			{
 				claimedAttributes = Asn1Sequence.GetInstance(taggedObject, true);
diff --git a/crypto/src/asn1/isismtt/x509/AdmissionSyntax.cs b/crypto/src/asn1/isismtt/x509/AdmissionSyntax.cs
index eac5d9a1a..424d73c69 100644
--- a/crypto/src/asn1/isismtt/x509/AdmissionSyntax.cs
+++ b/crypto/src/asn1/isismtt/x509/AdmissionSyntax.cs
@@ -172,20 +172,19 @@ namespace Org.BouncyCastle.Asn1.IsisMtt.X509
         *
         * @param seq The ASN.1 sequence.
         */
-        private AdmissionSyntax(
-            Asn1Sequence seq)
+        private AdmissionSyntax(Asn1Sequence seq)
         {
             switch (seq.Count)
             {
-                case 1:
-                    this.contentsOfAdmissions = DerSequence.GetInstance(seq[0]);
-                    break;
-                case 2:
-                    admissionAuthority = GeneralName.GetInstance(seq[0]);
-                    contentsOfAdmissions = DerSequence.GetInstance(seq[1]);
-                    break;
-                default:
-                    throw new ArgumentException("Bad sequence size: " + seq.Count);
+            case 1:
+                this.contentsOfAdmissions = Asn1Sequence.GetInstance(seq[0]);
+                break;
+            case 2:
+                admissionAuthority = GeneralName.GetInstance(seq[0]);
+                contentsOfAdmissions = Asn1Sequence.GetInstance(seq[1]);
+                break;
+            default:
+                throw new ArgumentException("Bad sequence size: " + seq.Count);
             }
         }
 
diff --git a/crypto/src/asn1/nist/KMACwithSHAKE128_params.cs b/crypto/src/asn1/nist/KMACwithSHAKE128_params.cs
index df2bf0173..ca94b5bfe 100644
--- a/crypto/src/asn1/nist/KMACwithSHAKE128_params.cs
+++ b/crypto/src/asn1/nist/KMACwithSHAKE128_params.cs
@@ -56,9 +56,9 @@ public class KMacWithShake128Params : Asn1Encodable
         }
         else if (seq.Count == 1)
         {
-            if (seq[0] is DerInteger)
+            if (seq[0] is DerInteger derInteger)
             {
-                this.outputLength = DerInteger.GetInstance(seq[0]).IntValueExact;
+                this.outputLength = derInteger.IntValueExact;
                 this.customizationString = EMPTY_STRING;
             }
             else
diff --git a/crypto/src/asn1/nist/KMACwithSHAKE256_params.cs b/crypto/src/asn1/nist/KMACwithSHAKE256_params.cs
index dfdfb2c36..99f444e7f 100644
--- a/crypto/src/asn1/nist/KMACwithSHAKE256_params.cs
+++ b/crypto/src/asn1/nist/KMACwithSHAKE256_params.cs
@@ -55,9 +55,9 @@ public class KMacWithShake256Params : Asn1Encodable
         }
         else if (seq.Count == 1)
         {
-            if (seq[0] is DerInteger)
+            if (seq[0] is DerInteger derInteger)
             {
-                this.outputLength = DerInteger.GetInstance(seq[0]).IntValueExact;
+                this.outputLength = derInteger.IntValueExact;
                 this.customizationString = EMPTY_STRING;
             }
             else
diff --git a/crypto/src/asn1/ocsp/ResponderID.cs b/crypto/src/asn1/ocsp/ResponderID.cs
index 143b17339..bc8b7f731 100644
--- a/crypto/src/asn1/ocsp/ResponderID.cs
+++ b/crypto/src/asn1/ocsp/ResponderID.cs
@@ -10,27 +10,22 @@ namespace Org.BouncyCastle.Asn1.Ocsp
     {
         private readonly Asn1Encodable id;
 
-		public static ResponderID GetInstance(
-			object obj)
+		public static ResponderID GetInstance(object obj)
 		{
 			if (obj == null || obj is ResponderID)
 			{
 				return (ResponderID)obj;
 			}
 
-			if (obj is DerOctetString)
+			if (obj is Asn1OctetString octets)
 			{
-				return new ResponderID((DerOctetString)obj);
+				return new ResponderID(octets);
 			}
 
-			if (obj is Asn1TaggedObject)
+			if (obj is Asn1TaggedObject o)
 			{
-				Asn1TaggedObject o = (Asn1TaggedObject)obj;
-
 				if (o.TagNo == 1)
-				{
 					return new ResponderID(X509Name.GetInstance(o, true));
-				}
 
 				return new ResponderID(Asn1OctetString.GetInstance(o, true));
 			}
diff --git a/crypto/src/asn1/ocsp/ResponseData.cs b/crypto/src/asn1/ocsp/ResponseData.cs
index b18e1d623..b79301997 100644
--- a/crypto/src/asn1/ocsp/ResponseData.cs
+++ b/crypto/src/asn1/ocsp/ResponseData.cs
@@ -63,16 +63,13 @@ namespace Org.BouncyCastle.Asn1.Ocsp
 		{
 		}
 
-		private ResponseData(
-			Asn1Sequence seq)
+		private ResponseData(Asn1Sequence seq)
 		{
 			int index = 0;
 
 			Asn1Encodable enc = seq[0];
-			if (enc is Asn1TaggedObject)
+			if (enc is Asn1TaggedObject o)
 			{
-				Asn1TaggedObject o = (Asn1TaggedObject)enc;
-
 				if (o.TagNo == 0)
 				{
 					this.versionPresent = true;
diff --git a/crypto/src/asn1/pkcs/CertificationRequestInfo.cs b/crypto/src/asn1/pkcs/CertificationRequestInfo.cs
index b775014b2..795757533 100644
--- a/crypto/src/asn1/pkcs/CertificationRequestInfo.cs
+++ b/crypto/src/asn1/pkcs/CertificationRequestInfo.cs
@@ -71,7 +71,7 @@ namespace Org.BouncyCastle.Asn1.Pkcs
             //
             if (seq.Count > 3)
             {
-                DerTaggedObject tagobj = (DerTaggedObject) seq[3];
+                Asn1TaggedObject tagobj = (Asn1TaggedObject)seq[3];
                 attributes = Asn1Set.GetInstance(tagobj, false);
             }
 
diff --git a/crypto/src/asn1/pkcs/EncryptedData.cs b/crypto/src/asn1/pkcs/EncryptedData.cs
index cb04f343c..fdee60405 100644
--- a/crypto/src/asn1/pkcs/EncryptedData.cs
+++ b/crypto/src/asn1/pkcs/EncryptedData.cs
@@ -86,7 +86,7 @@ namespace Org.BouncyCastle.Asn1.Pkcs
 			{
 				if (data.Count == 3)
 				{
-					DerTaggedObject o = (DerTaggedObject) data[2];
+                    Asn1TaggedObject o = (Asn1TaggedObject)data[2];
 
 					return Asn1OctetString.GetInstance(o, false);
 				}
diff --git a/crypto/src/asn1/pkcs/SafeBag.cs b/crypto/src/asn1/pkcs/SafeBag.cs
index 0ec9fa4ad..0c4f3972b 100644
--- a/crypto/src/asn1/pkcs/SafeBag.cs
+++ b/crypto/src/asn1/pkcs/SafeBag.cs
@@ -42,7 +42,7 @@ namespace Org.BouncyCastle.Asn1.Pkcs
 		private SafeBag(Asn1Sequence seq)
         {
             this.bagID = (DerObjectIdentifier)seq[0];
-            this.bagValue = ((DerTaggedObject)seq[1]).GetObject();
+            this.bagValue = ((Asn1TaggedObject)seq[1]).GetObject();
             if (seq.Count == 3)
             {
                 this.bagAttributes = (Asn1Set)seq[2];
diff --git a/crypto/src/asn1/tsp/Accuracy.cs b/crypto/src/asn1/tsp/Accuracy.cs
index 0d64e2dd4..f9cd88014 100644
--- a/crypto/src/asn1/tsp/Accuracy.cs
+++ b/crypto/src/asn1/tsp/Accuracy.cs
@@ -40,20 +40,17 @@ namespace Org.BouncyCastle.Asn1.Tsp
             this.micros = micros;
 		}
 
-		private Accuracy(
-			Asn1Sequence seq)
+		private Accuracy(Asn1Sequence seq)
 		{
 			for (int i = 0; i < seq.Count; ++i)
 			{
 				// seconds
-				if (seq[i] is DerInteger)
+				if (seq[i] is DerInteger derInteger)
 				{
-					seconds = (DerInteger) seq[i];
+					seconds = derInteger;
 				}
-                else if (seq[i] is Asn1TaggedObject)
+                else if (seq[i] is Asn1TaggedObject extra)
 				{
-                    Asn1TaggedObject extra = (Asn1TaggedObject)seq[i];
-
                     switch (extra.TagNo)
                     {
                     case 0:
diff --git a/crypto/src/asn1/tsp/TSTInfo.cs b/crypto/src/asn1/tsp/TSTInfo.cs
index c37208d3c..a8e166cbc 100644
--- a/crypto/src/asn1/tsp/TSTInfo.cs
+++ b/crypto/src/asn1/tsp/TSTInfo.cs
@@ -58,10 +58,8 @@ namespace Org.BouncyCastle.Asn1.Tsp
 			{
 				Asn1Object o = (Asn1Object) e.Current;
 
-				if (o is Asn1TaggedObject)
+				if (o is Asn1TaggedObject tagged)
 				{
-					DerTaggedObject tagged = (DerTaggedObject) o;
-
 					switch (tagged.TagNo)
 					{
 					case 0:
@@ -75,7 +73,7 @@ namespace Org.BouncyCastle.Asn1.Tsp
 					}
 				}
 
-				if (o is DerSequence)
+				if (o is Asn1Sequence)
 				{
 					accuracy = Accuracy.GetInstance(o);
 				}
diff --git a/crypto/src/asn1/tsp/TimeStampReq.cs b/crypto/src/asn1/tsp/TimeStampReq.cs
index 7173172c4..027c0a45b 100644
--- a/crypto/src/asn1/tsp/TimeStampReq.cs
+++ b/crypto/src/asn1/tsp/TimeStampReq.cs
@@ -24,8 +24,7 @@ namespace Org.BouncyCastle.Asn1.Tsp
             return new TimeStampReq(Asn1Sequence.GetInstance(obj));
         }
 
-        private TimeStampReq(
-			Asn1Sequence seq)
+        private TimeStampReq(Asn1Sequence seq)
 		{
 			int nbObjects = seq.Count;
 			int seqStart = 0;
@@ -39,24 +38,23 @@ namespace Org.BouncyCastle.Asn1.Tsp
 			for (int opt = seqStart; opt < nbObjects; opt++)
 			{
 				// tsaPolicy
-				if (seq[opt] is DerObjectIdentifier)
+				if (seq[opt] is DerObjectIdentifier oid)
 				{
-					tsaPolicy = DerObjectIdentifier.GetInstance(seq[opt]);
+					tsaPolicy = oid;
 				}
 				// nonce
-				else if (seq[opt] is DerInteger)
+				else if (seq[opt] is DerInteger derInteger)
 				{
-					nonce = DerInteger.GetInstance(seq[opt]);
+					nonce = derInteger;
 				}
 				// certReq
-				else if (seq[opt] is DerBoolean)
+				else if (seq[opt] is DerBoolean derBoolean)
 				{
-					certReq = DerBoolean.GetInstance(seq[opt]);
+					certReq = derBoolean;
 				}
 				// extensions
-				else if (seq[opt] is Asn1TaggedObject)
+				else if (seq[opt] is Asn1TaggedObject tagged)
 				{
-					Asn1TaggedObject tagged = (Asn1TaggedObject) seq[opt];
 					if (tagged.TagNo == 0)
 					{
 						extensions = X509Extensions.GetInstance(tagged, false);
diff --git a/crypto/src/asn1/x509/AttributeCertificateInfo.cs b/crypto/src/asn1/x509/AttributeCertificateInfo.cs
index d466bbd14..dde432ee6 100644
--- a/crypto/src/asn1/x509/AttributeCertificateInfo.cs
+++ b/crypto/src/asn1/x509/AttributeCertificateInfo.cs
@@ -69,11 +69,11 @@ namespace Org.BouncyCastle.Asn1.X509
 
 			for (int i = start + 6; i < seq.Count; i++)
             {
-                Asn1Encodable obj = (Asn1Encodable) seq[i];
+                Asn1Encodable obj = seq[i];
 
-				if (obj is DerBitString)
+				if (obj is DerBitString bitString)
                 {
-                    this.issuerUniqueID = DerBitString.GetInstance(seq[i]);
+                    this.issuerUniqueID = bitString;
                 }
                 else if (obj is Asn1Sequence || obj is X509Extensions)
                 {
diff --git a/crypto/src/asn1/x509/BasicConstraints.cs b/crypto/src/asn1/x509/BasicConstraints.cs
index deecae241..acc8766a7 100644
--- a/crypto/src/asn1/x509/BasicConstraints.cs
+++ b/crypto/src/asn1/x509/BasicConstraints.cs
@@ -37,9 +37,9 @@ namespace Org.BouncyCastle.Asn1.X509
         {
 			if (seq.Count > 0)
 			{
-				if (seq[0] is DerBoolean)
+				if (seq[0] is DerBoolean derBoolean)
 				{
-					this.cA = DerBoolean.GetInstance(seq[0]);
+					this.cA = derBoolean;
 				}
 				else
 				{
diff --git a/crypto/src/asn1/x509/NoticeReference.cs b/crypto/src/asn1/x509/NoticeReference.cs
index 2fb275d8f..22bb35b71 100644
--- a/crypto/src/asn1/x509/NoticeReference.cs
+++ b/crypto/src/asn1/x509/NoticeReference.cs
@@ -120,14 +120,7 @@ namespace Org.BouncyCastle.Asn1.X509
 
         public virtual DerInteger[] GetNoticeNumbers()
         {
-            DerInteger[] tmp = new DerInteger[noticeNumbers.Count];
-
-            for (int i = 0; i != noticeNumbers.Count; ++i)
-            {
-                tmp[i] = DerInteger.GetInstance(noticeNumbers[i]);
-            }
-
-            return tmp;
+            return noticeNumbers.MapElements(DerInteger.GetInstance);
         }
 
         /**
diff --git a/crypto/src/asn1/x509/TBSCertList.cs b/crypto/src/asn1/x509/TBSCertList.cs
index 009773e79..4cfb44c90 100644
--- a/crypto/src/asn1/x509/TBSCertList.cs
+++ b/crypto/src/asn1/x509/TBSCertList.cs
@@ -169,21 +169,19 @@ namespace Org.BouncyCastle.Asn1.X509
             throw new ArgumentException("unknown object in factory: " + Platform.GetTypeName(obj), "obj");
         }
 
-		internal TbsCertificateList(
-            Asn1Sequence seq)
+		internal TbsCertificateList(Asn1Sequence seq)
         {
 			if (seq.Count < 3 || seq.Count > 7)
-			{
 				throw new ArgumentException("Bad sequence size: " + seq.Count);
-			}
 
 			int seqPos = 0;
 
 			this.seq = seq;
 
-			if (seq[seqPos] is DerInteger)
+			if (seq[seqPos] is DerInteger derInteger)
             {
-				version = DerInteger.GetInstance(seq[seqPos++]);
+				version = derInteger;
+				++seqPos;
 			}
             else
             {
diff --git a/crypto/src/asn1/x509/TBSCertificateStructure.cs b/crypto/src/asn1/x509/TBSCertificateStructure.cs
index 5e3bf2601..e1fba2488 100644
--- a/crypto/src/asn1/x509/TBSCertificateStructure.cs
+++ b/crypto/src/asn1/x509/TBSCertificateStructure.cs
@@ -66,11 +66,11 @@ namespace Org.BouncyCastle.Asn1.X509
 			this.seq = seq;
 
 			//
-			// some certficates don't include a version number - we assume v1
+			// some certificates don't include a version number - we assume v1
 			//
-			if (seq[0] is Asn1TaggedObject)
+			if (seq[0] is Asn1TaggedObject taggedObject)
 			{
-				version = DerInteger.GetInstance((Asn1TaggedObject)seq[0], true);
+				version = DerInteger.GetInstance(taggedObject, true);
 			}
 			else
 			{
diff --git a/crypto/src/asn1/x9/X9ECParameters.cs b/crypto/src/asn1/x9/X9ECParameters.cs
index 077f74ce4..0f6d85765 100644
--- a/crypto/src/asn1/x9/X9ECParameters.cs
+++ b/crypto/src/asn1/x9/X9ECParameters.cs
@@ -54,9 +54,9 @@ namespace Org.BouncyCastle.Asn1.X9
             this.curve = x9c.Curve;
             object p = seq[3];
 
-            if (p is X9ECPoint)
+            if (p is X9ECPoint x9)
             {
-                this.g = (X9ECPoint)p;
+                this.g = x9;
             }
             else
             {