diff --git a/CardinalityEstimation/CardinalityEstimation.csproj b/CardinalityEstimation/CardinalityEstimation.csproj
index 1870c90..55724b3 100644
--- a/CardinalityEstimation/CardinalityEstimation.csproj
+++ b/CardinalityEstimation/CardinalityEstimation.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
-        <TargetFrameworks>net9.0;net8.0</TargetFrameworks>
+        <TargetFrameworks>net9.0;net8.0;netstandard2.0</TargetFrameworks>
+		<LangVersion>latest</LangVersion>
         <Configurations>Debug;Release;Release-Signed</Configurations>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <PackageId Condition=" '$(Configuration)' == 'Release-Signed' ">CardinalityEstimation.Signed</PackageId>
diff --git a/CardinalityEstimation/CardinalityEstimator.cs b/CardinalityEstimation/CardinalityEstimator.cs
index ae526c1..08aa788 100644
--- a/CardinalityEstimation/CardinalityEstimator.cs
+++ b/CardinalityEstimation/CardinalityEstimator.cs
@@ -27,6 +27,7 @@ namespace CardinalityEstimation
 {
     using System;
     using System.Collections.Generic;
+    using System.Numerics;
     using System.Text;
     using Hash;
 
@@ -214,8 +215,8 @@ internal CardinalityEstimator(GetHashCodeDelegate hashFunction, CardinalityEstim
             this.hashFunction = hashFunction;
             if (this.hashFunction == null)
             {
-                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
-                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
+                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
+                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
             }
             else
             {
@@ -237,8 +238,8 @@ internal CardinalityEstimator(GetHashCodeSpanDelegate hashFunctionSpan, Cardinal
             this.hashFunctionSpan = hashFunctionSpan;
             if (this.hashFunctionSpan == null)
             {
-                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
-                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
+                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
+                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
             }
             else
             {
@@ -846,7 +847,7 @@ public static byte GetSigma(ulong hash, byte bitsToCount)
             int knownZeros = 64 - bitsToCount;
 
             var masked = hash & mask;
-            var leadingZeros = (byte)ulong.LeadingZeroCount(masked);
+            var leadingZeros = (byte)BitOperations.LeadingZeroCount(masked);
             return (byte)(leadingZeros - knownZeros + 1);
         }
 
diff --git a/CardinalityEstimation/ConcurrentCardinalityEstimator.cs b/CardinalityEstimation/ConcurrentCardinalityEstimator.cs
index cb8e985..0893d9a 100644
--- a/CardinalityEstimation/ConcurrentCardinalityEstimator.cs
+++ b/CardinalityEstimation/ConcurrentCardinalityEstimator.cs
@@ -168,7 +168,7 @@ public ConcurrentCardinalityEstimator(CardinalityEstimator other)
             lockSlim = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);
 
             // Init the hash function - use default since we can't get it from the other estimator
-            hashFunction = ((x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x)));
+            hashFunction = ((x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0));
 
             sparseMaxElements = Math.Max(0, (m / 15) - 10);
 
@@ -217,8 +217,8 @@ internal ConcurrentCardinalityEstimator(GetHashCodeDelegate hashFunction, Cardin
             this.hashFunction = hashFunction;
             if (this.hashFunction == null)
             {
-                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
-                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
+                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
+                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
             }
             else
             {
@@ -237,8 +237,8 @@ internal ConcurrentCardinalityEstimator(GetHashCodeSpanDelegate hashFunctionSpan
             this.hashFunctionSpan = hashFunctionSpan;
             if (this.hashFunction == null)
             {
-                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
-                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x));
+                this.hashFunction = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
+                this.hashFunctionSpan = (x) => BitConverter.ToUInt64(System.IO.Hashing.XxHash128.Hash(x), 0);
             }
         }
 
diff --git a/CardinalityEstimation/Polyfills/BitOperations.cs b/CardinalityEstimation/Polyfills/BitOperations.cs
new file mode 100644
index 0000000..cb84892
--- /dev/null
+++ b/CardinalityEstimation/Polyfills/BitOperations.cs
@@ -0,0 +1,26 @@
+#if !NETCOREAPP3_0_OR_GREATER
+namespace System.Numerics;
+
+internal static class BitOperations
+{
+    public static uint LeadingZeroCount(ulong x)
+    {
+        x |= x >> 1;
+        x |= x >> 2;
+        x |= x >> 4;
+        x |= x >> 8;
+        x |= x >> 16;
+        x |= x >> 32;
+
+        x -= x >> 1 & 0x5555555555555555;
+        x = (x >> 2 & 0x3333333333333333) + (x & 0x3333333333333333);
+        x = (x >> 4) + x & 0x0f0f0f0f0f0f0f0f;
+        x += x >> 8;
+        x += x >> 16;
+        x += x >> 32;
+
+        const int numLongBits = sizeof(long) * 8;
+        return numLongBits - (uint)(x & 0x0000007f);
+    }
+}
+#endif
diff --git a/CardinalityEstimation/Polyfills/Linq.cs b/CardinalityEstimation/Polyfills/Linq.cs
new file mode 100644
index 0000000..940a7f2
--- /dev/null
+++ b/CardinalityEstimation/Polyfills/Linq.cs
@@ -0,0 +1,13 @@
+#if !NETCOREAPP2_1_OR_GREATER
+using System.Collections.Generic;
+
+namespace System.Linq;
+
+internal static class LinqExtensions
+{
+    public static HashSet<T> ToHashSet<T>(this IEnumerable<T> source)
+    {
+        return new(source);
+    }
+}
+#endif
\ No newline at end of file