Implement generic IEnumerable on various X509 collection types

X509Certificate2Collection gets it, X509CertificateCollection doesn't.

We don't really want people using the older collection type, and we have inheritance, and being both
`IEnumerable<X509Certificate>` and `IEnumerable<X509Certificate2>` makes some things weird.

src/libraries/System.Security.Cryptography.X509Certificates/ref/System.Security.Cryptography.X509Certificates.cs

@@ -278,7 +278,7 @@ public partial class X509Certificate2 : System.Security.Cryptography.X509Certifi
         public override string ToString(bool verbose) { throw null; }
         public bool Verify() { throw null; }
     }
-    public partial class X509Certificate2Collection : System.Security.Cryptography.X509Certificates.X509CertificateCollection
+    public partial class X509Certificate2Collection : System.Security.Cryptography.X509Certificates.X509CertificateCollection, System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509Certificate2>, System.Collections.IEnumerable
     {
         public X509Certificate2Collection() { }
         public X509Certificate2Collection(System.Security.Cryptography.X509Certificates.X509Certificate2 certificate) { }
@@ -307,8 +307,9 @@ public partial class X509Certificate2Collection : System.Security.Cryptography.X
         public void Remove(System.Security.Cryptography.X509Certificates.X509Certificate2 certificate) { }
         public void RemoveRange(System.Security.Cryptography.X509Certificates.X509Certificate2Collection certificates) { }
         public void RemoveRange(System.Security.Cryptography.X509Certificates.X509Certificate2[] certificates) { }
+        System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509Certificate2> System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509Certificate2>.GetEnumerator() { throw null; }
     }
-    public sealed partial class X509Certificate2Enumerator : System.Collections.IEnumerator
+    public sealed partial class X509Certificate2Enumerator : System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509Certificate2>, System.Collections.IEnumerator, System.IDisposable
     {
         internal X509Certificate2Enumerator() { }
         public System.Security.Cryptography.X509Certificates.X509Certificate2 Current { get { throw null; } }
@@ -317,6 +318,7 @@ public sealed partial class X509Certificate2Enumerator : System.Collections.IEnu
         public void Reset() { }
         bool System.Collections.IEnumerator.MoveNext() { throw null; }
         void System.Collections.IEnumerator.Reset() { }
+        void System.IDisposable.Dispose() { }
     }
     public partial class X509CertificateCollection : System.Collections.CollectionBase
     {
@@ -370,7 +372,7 @@ public partial class X509ChainElement
         public System.Security.Cryptography.X509Certificates.X509ChainStatus[] ChainElementStatus { get { throw null; } }
         public string Information { get { throw null; } }
     }
-    public sealed partial class X509ChainElementCollection : System.Collections.ICollection, System.Collections.IEnumerable
+    public sealed partial class X509ChainElementCollection : System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509ChainElement>, System.Collections.ICollection, System.Collections.IEnumerable
     {
         internal X509ChainElementCollection() { }
         public int Count { get { throw null; } }
@@ -379,16 +381,18 @@ public sealed partial class X509ChainElementCollection : System.Collections.ICol
         public object SyncRoot { get { throw null; } }
         public void CopyTo(System.Security.Cryptography.X509Certificates.X509ChainElement[] array, int index) { }
         public System.Security.Cryptography.X509Certificates.X509ChainElementEnumerator GetEnumerator() { throw null; }
+        System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509ChainElement> System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509ChainElement>.GetEnumerator() { throw null; }
         void System.Collections.ICollection.CopyTo(System.Array array, int index) { }
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
     }
-    public sealed partial class X509ChainElementEnumerator : System.Collections.IEnumerator
+    public sealed partial class X509ChainElementEnumerator : System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509ChainElement>, System.Collections.IEnumerator, System.IDisposable
     {
         internal X509ChainElementEnumerator() { }
         public System.Security.Cryptography.X509Certificates.X509ChainElement Current { get { throw null; } }
         object System.Collections.IEnumerator.Current { get { throw null; } }
         public bool MoveNext() { throw null; }
         public void Reset() { }
+        void System.IDisposable.Dispose() { }
     }
     public sealed partial class X509ChainPolicy
     {
@@ -479,7 +483,7 @@ public partial class X509Extension : System.Security.Cryptography.AsnEncodedData
         public bool Critical { get { throw null; } set { } }
         public override void CopyFrom(System.Security.Cryptography.AsnEncodedData asnEncodedData) { }
     }
-    public sealed partial class X509ExtensionCollection : System.Collections.ICollection, System.Collections.IEnumerable
+    public sealed partial class X509ExtensionCollection : System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509Extension>, System.Collections.ICollection, System.Collections.IEnumerable
     {
         public X509ExtensionCollection() { }
         public int Count { get { throw null; } }
@@ -490,16 +494,18 @@ public sealed partial class X509ExtensionCollection : System.Collections.ICollec
         public int Add(System.Security.Cryptography.X509Certificates.X509Extension extension) { throw null; }
         public void CopyTo(System.Security.Cryptography.X509Certificates.X509Extension[] array, int index) { }
         public System.Security.Cryptography.X509Certificates.X509ExtensionEnumerator GetEnumerator() { throw null; }
+        System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509Extension> System.Collections.Generic.IEnumerable<System.Security.Cryptography.X509Certificates.X509Extension>.GetEnumerator() { throw null; }
         void System.Collections.ICollection.CopyTo(System.Array array, int index) { }
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
     }
-    public sealed partial class X509ExtensionEnumerator : System.Collections.IEnumerator
+    public sealed partial class X509ExtensionEnumerator : System.Collections.Generic.IEnumerator<System.Security.Cryptography.X509Certificates.X509Extension>, System.Collections.IEnumerator, System.IDisposable
     {
         internal X509ExtensionEnumerator() { }
         public System.Security.Cryptography.X509Certificates.X509Extension Current { get { throw null; } }
         object System.Collections.IEnumerator.Current { get { throw null; } }
         public bool MoveNext() { throw null; }
         public void Reset() { }
+        void System.IDisposable.Dispose() { }
     }
     public enum X509FindType
     {

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509Certificate2Collection.cs

@@ -7,10 +7,11 @@
 using System.Diagnostics;
 using System.Formats.Asn1;
 using System.Security.Cryptography.X509Certificates.Asn1;
+using System.Collections.Generic;
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public class X509Certificate2Collection : X509CertificateCollection
+    public class X509Certificate2Collection : X509CertificateCollection, IEnumerable<X509Certificate2>
     {
         public X509Certificate2Collection()
         {
@@ -133,6 +134,8 @@ public new X509Certificate2Enumerator GetEnumerator()
             return new X509Certificate2Enumerator(this);
         }
 
+        IEnumerator<X509Certificate2> IEnumerable<X509Certificate2>.GetEnumerator() => GetEnumerator();
+
         public void Import(byte[] rawData)
         {
             if (rawData == null)

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509Certificate2Enumerator.cs

@@ -2,11 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public sealed class X509Certificate2Enumerator : IEnumerator
+    public sealed class X509Certificate2Enumerator : IEnumerator, IEnumerator<X509Certificate2>
     {
         private readonly IEnumerator _enumerator;
 
@@ -46,5 +47,8 @@ void IEnumerator.Reset()
         {
             Reset();
         }
+        void IDisposable.Dispose()
+        {
+        }
     }
 }

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509ChainElementCollection.cs

@@ -2,11 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public sealed class X509ChainElementCollection : ICollection, IEnumerable
+    public sealed class X509ChainElementCollection : ICollection, IEnumerable<X509ChainElement>
     {
         private readonly X509ChainElement[] _elements;
 
@@ -81,5 +82,7 @@ IEnumerator IEnumerable.GetEnumerator()
         {
             return new X509ChainElementEnumerator(this);
         }
+
+        IEnumerator<X509ChainElement> IEnumerable<X509ChainElement>.GetEnumerator() => GetEnumerator();
     }
 }

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509ChainElementEnumerator.cs

@@ -2,10 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
+using System.Collections.Generic;
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public sealed class X509ChainElementEnumerator : IEnumerator
+    public sealed class X509ChainElementEnumerator : IEnumerator, IEnumerator<X509ChainElement>
     {
         private readonly X509ChainElementCollection _chainElements;
         private int _current;
@@ -32,6 +33,10 @@ object IEnumerator.Current
             }
         }
 
+        void IDisposable.Dispose()
+        {
+        }
+
         public bool MoveNext()
         {
             if (_current == _chainElements.Count - 1)

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509ExtensionCollection.cs

@@ -14,7 +14,7 @@
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public sealed class X509ExtensionCollection : ICollection, IEnumerable
+    public sealed class X509ExtensionCollection : ICollection, IEnumerable<X509Extension>
     {
         public X509ExtensionCollection()
         {
@@ -103,6 +103,8 @@ IEnumerator IEnumerable.GetEnumerator()
             return new X509ExtensionEnumerator(this);
         }
 
+        IEnumerator<X509Extension> IEnumerable<X509Extension>.GetEnumerator() => GetEnumerator();
+
         private readonly List<X509Extension> _list = new List<X509Extension>();
     }
 }

src/libraries/System.Security.Cryptography.X509Certificates/src/System/Security/Cryptography/X509Certificates/X509ExtensionEnumerator.cs

@@ -2,10 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
+using System.Collections.Generic;
 
 namespace System.Security.Cryptography.X509Certificates
 {
-    public sealed class X509ExtensionEnumerator : IEnumerator
+    public sealed class X509ExtensionEnumerator : IEnumerator, IEnumerator<X509Extension>
     {
         internal X509ExtensionEnumerator(X509ExtensionCollection extensions)
         {
@@ -36,6 +37,10 @@ public void Reset()
             _current = -1;
         }
 
+        void IDisposable.Dispose()
+        {
+        }
+
         private readonly X509ExtensionCollection _extensions;
         private int _current;
     }

src/libraries/System.Security.Cryptography.X509Certificates/tests/ChainTests.cs

@@ -1067,7 +1067,6 @@ public static void BuildChainForFraudulentCertificate()
                 else
                 {
                     X509ChainElement certElement = chain.ChainElements
-                        .OfType<X509ChainElement>()
                         .Single(e => e.Certificate.Subject == cert.Subject);
 
                     const X509ChainStatusFlags ExpectedFlag = X509ChainStatusFlags.ExplicitDistrust;
@@ -1154,7 +1153,6 @@ public static void BuildChainForCertificateSignedWithDisallowedKey()
                 else
                 {
                     X509ChainElement certElement = chain.ChainElements
-                        .OfType<X509ChainElement>()
                         .Single(e => e.Certificate.Subject == intermediateCert.Subject);
 
                     const X509ChainStatusFlags ExpectedFlag = X509ChainStatusFlags.ExplicitDistrust;

src/libraries/System.Security.Cryptography.X509Certificates/tests/CollectionImportTests.cs

@@ -383,7 +383,7 @@ public static void ImportPkcs12File_Chain_VerifyContents(X509KeyStorageFlags key
                     "test.local",
                 };
 
-                string[] actualSubjects = certs.OfType<X509Certificate2>().
+                string[] actualSubjects = certs.
                     Select(cert => cert.GetNameInfo(X509NameType.SimpleName, false)).
                     ToArray();
 
@@ -397,7 +397,7 @@ public static void ImportPkcs12File_Chain_VerifyContents(X509KeyStorageFlags key
                     true,
                 };
 
-                bool[] actualHasPrivateKeys = certs.OfType<X509Certificate2>().
+                bool[] actualHasPrivateKeys = certs.
                     Select(cert => cert.HasPrivateKey).
                     ToArray();
 

src/libraries/System.Security.Cryptography.X509Certificates/tests/CollectionTests.cs

@@ -773,7 +773,7 @@ public static void ExportUnrelatedPfx()
 
                     // But, really, the collections should be equivalent
                     // (after being coerced to IEnumerable<X509Certificate2>)
-                    Assert.Equal(collection.OfType<X509Certificate2>(), importedCollection.OfType<X509Certificate2>());
+                    Assert.Equal(collection, importedCollection);
                 }
             }
         }
@@ -808,7 +808,7 @@ public static void ExportMultiplePrivateKeys()
                 collection.Import(TestData.PfxData, TestData.PfxDataPassword, X509KeyStorageFlags.Exportable | Cert.EphemeralIfPossible);
 
                 // Pre-condition, we have multiple private keys
-                int originalPrivateKeyCount = collection.OfType<X509Certificate2>().Count(c => c.HasPrivateKey);
+                int originalPrivateKeyCount = collection.Count(c => c.HasPrivateKey);
                 Assert.Equal(2, originalPrivateKeyCount);
 
                 byte[] exported = collection.Export(X509ContentType.Pkcs12);
@@ -819,7 +819,7 @@ public static void ExportMultiplePrivateKeys()
 
                     Assert.Equal(collection.Count, importedCollection.Count);
 
-                    int importedPrivateKeyCount = importedCollection.OfType<X509Certificate2>().Count(c => c.HasPrivateKey);
+                    int importedPrivateKeyCount = importedCollection.Count(c => c.HasPrivateKey);
                     Assert.Equal(originalPrivateKeyCount, importedPrivateKeyCount);
                 }
             }
@@ -846,7 +846,7 @@ public static void CanAddMultipleCertsWithSinglePrivateKey()
                     twoWithoutKey,
                 };
 
-                Assert.Equal(1, col.Cast<X509Certificate2>().Count(x => x.HasPrivateKey));
+                Assert.Equal(1, col.Count(x => x.HasPrivateKey));
                 Assert.Equal(2, col.Count);
 
                 byte[] buffer = col.Export(X509ContentType.Pfx);
@@ -1616,15 +1616,5 @@ private static void TestExportStore(X509ContentType ct)
         }
 
         public static IEnumerable<object[]> StorageFlags => CollectionImportTests.StorageFlags;
-
-        private static X509Certificate2[] ToArray(this X509Certificate2Collection col)
-        {
-            X509Certificate2[] array = new X509Certificate2[col.Count];
-            for (int i = 0; i < col.Count; i++)
-            {
-                array[i] = col[i];
-            }
-            return array;
-        }
     }
 }

src/libraries/System.Security.Cryptography.X509Certificates/tests/DynamicChainTests.cs

@@ -357,7 +357,7 @@ public static void TestLeafCertificateWithUnknownCriticalExtension()
                     }
                     else
                     {
-                        X509ChainElement certElement = chain.ChainElements.OfType<X509ChainElement>().Single();
+                        X509ChainElement certElement = chain.ChainElements.Single();
                         const X509ChainStatusFlags ExpectedFlag = X509ChainStatusFlags.HasNotSupportedCriticalExtension;
                         X509ChainStatusFlags actualFlags = certElement.AllStatusFlags();
                         Assert.True((actualFlags & ExpectedFlag) == ExpectedFlag, $"Has expected flag {ExpectedFlag} but was {actualFlags}");

src/libraries/System.Security.Cryptography.X509Certificates/tests/RevocationTests/TimeoutTests.cs

@@ -340,7 +340,7 @@ public static void AiaFetchTimeout()
         }
 
         private static X509ChainStatusFlags GetFlags(X509Chain chain, string thumbprint) =>
-            chain.ChainElements.OfType<X509ChainElement>().
+            chain.ChainElements.
                 Single(e => e.Certificate.Thumbprint == thumbprint).
                 ChainElementStatus.Aggregate((X509ChainStatusFlags)0, (a, e) => a | e.Status);
     }

src/libraries/System.Security.Cryptography.X509Certificates/tests/X509FilesystemTests.Unix.cs

@@ -634,7 +634,7 @@ private static void AssertEqualContents(X509Store storeA, X509Store storeB)
                 X509Certificate2Collection storeACerts = storeATracker.Collection;
                 X509Certificate2Collection storeBCerts = storeBTracker.Collection;
 
-                Assert.Equal(storeACerts.OfType<X509Certificate2>(), storeBCerts.OfType<X509Certificate2>());
+                Assert.Equal(storeACerts, storeBCerts);
             }
         }