fix: Add NextBytes(Span<byte>) to RandomSource

src/Numerics/Numerics.csproj

@@ -2,7 +2,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>net5.0;net461;net48;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>net5.0;netcoreapp2.1;net461;net48;netstandard2.1;netstandard2.0</TargetFrameworks>
     <AssemblyName>MathNet.Numerics</AssemblyName>
     <RootNamespace>MathNet.Numerics</RootNamespace>
     <IsPackable>true</IsPackable>

src/Numerics/Random/RandomSource.cs

@@ -470,6 +470,27 @@ public sealed override void NextBytes(byte[] buffer)
             DoSampleBytes(buffer);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        /// <summary>
+        /// Fills the elements of a specified array of bytes with random numbers.
+        /// </summary>
+        /// <param name="buffer">An array of bytes to contain random numbers.</param>
+        public sealed override void NextBytes(Span<byte> buffer)
+        {
+            if (_threadSafe)
+            {
+                lock (_lock)
+                {
+                    DoSampleBytes(buffer);
+                }
+
+                return;
+            }
+
+            DoSampleBytes(buffer);
+        }
+#endif
+
         /// <summary>
         /// Returns a random number between 0.0 and 1.0.
         /// </summary>
@@ -511,6 +532,18 @@ protected virtual void DoSampleBytes(byte[] buffer)
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        /// <summary>
+        /// Fills the elements of a specified array of bytes with random numbers in full range, including zero and 255 (<see cref="F:System.Byte.MaxValue"/>).
+        /// </summary>
+        protected virtual void DoSampleBytes(Span<byte> buffer)
+        {
+            var temp = new byte[buffer.Length];
+            DoSampleBytes(temp);
+            temp.CopyTo(buffer);
+        }
+#endif
+
         /// <summary>
         /// Returns a random N-bit signed integer greater than or equal to zero and less than 2^N.
         /// N (bit count) is expected to be greater than zero and less than 32 (not verified).