address compiler warnings, swap rijndael for aes

src/UglyToad.PdfPig.Tests/Filters/AsciiHexDecodeFilterTests.cs

@@ -90,7 +90,9 @@
 
             var decoded = new AsciiHexDecodeFilter().Decode(input, dictionary, 1);
 
+#pragma warning disable SYSLIB0001
             var decodedText = Encoding.UTF7.GetString(decoded);
+#pragma warning restore SYSLIB0001
 
             Assert.Equal("®P", decodedText);
         }

src/UglyToad.PdfPig.Tests/Integration/AnnotationsTest.cs

@@ -28,8 +28,7 @@
             using (var doc = PdfDocument.Open(pdf))
             {
                 var annotations = doc.GetPage(1).ExperimentalAccess.GetAnnotations().ToArray();
-                Assert.Equal(1, annotations.Length);
-                var annotation = annotations[0];
+                var annotation = Assert.Single(annotations);
 
                 Assert.True(annotation.HasDownAppearance);
                 Assert.True(annotation.HasNormalAppearance);

src/UglyToad.PdfPig.Tests/Writer/PdfPageBuilderTests.cs

@@ -235,8 +235,6 @@
 
         private static void AddPageWithImage(PdfDocumentBuilder pdfBuilder, string subfolderName, string imageFileName, double imageHeight, PdfDocumentBuilder.AddedFont font)
         {
-             
-            var imageMargin = 20d;
             var imageBottom = 842d - 600d;
 
             //var imagePlacement = new PdfRectangle(0, imageTop, 595d, imageTop - imageHeight);

src/UglyToad.PdfPig/Encryption/AesEncryptionHelper.cs

@@ -21,14 +21,14 @@
             var iv = new byte[16];
             Array.Copy(data, iv, iv.Length);
 
-            using (var rijndael = Rijndael.Create())
+            using (var aes = Aes.Create())
             {
-                rijndael.Key = finalKey;
-                rijndael.IV = iv;
+                aes.Key = finalKey;
+                aes.IV = iv;
 
                 var buffer = new byte[256];
 
-                using (var decryptor = rijndael.CreateDecryptor(rijndael.Key, rijndael.IV))
+                using (var decryptor = aes.CreateDecryptor(aes.Key, aes.IV))
                 using (var input = new MemoryStream(data))
                 using (var output = new MemoryStream())
                 {

src/UglyToad.PdfPig/Encryption/EncryptionHandler.cs

@@ -685,15 +685,24 @@
 
             var iv = new byte[16];
 
-            using (var rijndaelManaged = new RijndaelManaged { Key = intermediateKey, IV = iv, Mode = CipherMode.CBC, Padding = PaddingMode.None })
-            using (var memoryStream = new MemoryStream(encryptedFileKey))
-            using (var output = new MemoryStream())
-            using (var cryptoStream = new CryptoStream(memoryStream, rijndaelManaged.CreateDecryptor(intermediateKey, iv), CryptoStreamMode.Read))
+            using (var aes = Aes.Create("AesManaged")!)
             {
-                cryptoStream.CopyTo(output);
-                var result = output.ToArray();
+                aes.Key = intermediateKey;
+                aes.IV = iv;
+                aes.Mode = CipherMode.CBC;
+                aes.Padding = PaddingMode.None;
 
-                return result;
+                using (var memoryStream = new MemoryStream(encryptedFileKey))
+                using (var output = new MemoryStream())
+                using (var cryptoStream = new CryptoStream(memoryStream,
+                           aes.CreateDecryptor(intermediateKey, iv),
+                           CryptoStreamMode.Read))
+                {
+                    cryptoStream.CopyTo(output);
+                    var result = output.ToArray();
+
+                    return result;
+                }
             }
         }