diff --git a/bench/algorithm/json-serde/1.cs b/bench/algorithm/json-serde/1.cs
index 38c529a9..69a856a9 100644
--- a/bench/algorithm/json-serde/1.cs
+++ b/bench/algorithm/json-serde/1.cs
@@ -32,14 +32,6 @@ private static void PrintHash(string s)
     {
         using var hasher = MD5.Create();
         var hash = hasher.ComputeHash(Encoding.UTF8.GetBytes(s));
-        Console.WriteLine(ToHexString(hash));
-    }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-            hex.AppendFormat("{0:x2}", b);
-        return hex.ToString();
+        Console.WriteLine(Convert.ToHexStringLower(hash));
     }
 }
diff --git a/bench/algorithm/json-serde/2.cs b/bench/algorithm/json-serde/2.cs
index 59db1463..8f58263b 100644
--- a/bench/algorithm/json-serde/2.cs
+++ b/bench/algorithm/json-serde/2.cs
@@ -30,7 +30,7 @@ private static void PrintHash(byte[] bytes)
     {
         using MD5 hasher = MD5.Create();
         byte[] hash = hasher.ComputeHash(bytes);
-        Console.WriteLine(Convert.ToHexString(hash).ToLower());
+        Console.WriteLine(Convert.ToHexStringLower(hash));
     }
 }
 internal sealed class GeoData
diff --git a/bench/algorithm/mandelbrot/1.cs b/bench/algorithm/mandelbrot/1.cs
index 6dc0152a..3e4ce5ef 100644
--- a/bench/algorithm/mandelbrot/1.cs
+++ b/bench/algorithm/mandelbrot/1.cs
@@ -42,7 +42,7 @@ public static void Main(string[] args)
 
         using var hasher = MD5.Create();
         var hash = hasher.ComputeHash(data);
-        Console.WriteLine(ToHexString(hash));
+        Console.WriteLine(Convert.ToHexStringLower(hash));
     }
 
     static byte mbrot8(double[] cr, double civ)
@@ -118,14 +118,4 @@ static void mul(Span<double> a, Span<double> b, Span<double> r)
             r[i] = a[i] * b[i];
         }
     }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-        {
-            hex.AppendFormat("{0:x2}", b);
-        }
-        return hex.ToString();
-    }
 }
diff --git a/bench/algorithm/mandelbrot/2.cs b/bench/algorithm/mandelbrot/2.cs
index c3336356..710e6fa2 100644
--- a/bench/algorithm/mandelbrot/2.cs
+++ b/bench/algorithm/mandelbrot/2.cs
@@ -44,7 +44,7 @@ public static void Main(string[] args)
 
         using var hasher = MD5.Create();
         var hash = hasher.ComputeHash(data);
-        Console.WriteLine(ToHexString(hash));
+        Console.WriteLine(Convert.ToHexStringLower(hash));
     }
 
     static byte mbrot8((Vector<double>, Vector<double>) cr, double civ)
@@ -103,14 +103,4 @@ static byte mbrot8((Vector<double>, Vector<double>) cr, double civ)
         }
         return accu;
     }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-        {
-            hex.AppendFormat("{0:x2}", b);
-        }
-        return hex.ToString();
-    }
 }
diff --git a/bench/algorithm/mandelbrot/3.cs b/bench/algorithm/mandelbrot/3.cs
index 19013996..bed812b3 100644
--- a/bench/algorithm/mandelbrot/3.cs
+++ b/bench/algorithm/mandelbrot/3.cs
@@ -92,7 +92,7 @@ public static void Main(string[] args)
 
         using var hasher = MD5.Create();
         var hash = hasher.ComputeHash(data);
-        Console.WriteLine(ToHexString(hash));
+        Console.WriteLine(Convert.ToHexStringLower(hash));
     }
 
     unsafe static byte mbrot8(F64x8 cr, double civ)
@@ -144,14 +144,4 @@ unsafe static byte mbrot8(F64x8 cr, double civ)
         }
         return accu;
     }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-        {
-            hex.AppendFormat("{0:x2}", b);
-        }
-        return hex.ToString();
-    }
 }
diff --git a/bench/algorithm/mandelbrot/9-m.cs b/bench/algorithm/mandelbrot/9-m.cs
index 075bbe70..d6ff10cc 100644
--- a/bench/algorithm/mandelbrot/9-m.cs
+++ b/bench/algorithm/mandelbrot/9-m.cs
@@ -83,17 +83,7 @@ public static unsafe void Main(string[] args)
             });
             using var hasher = MD5.Create();
             var hash = hasher.ComputeHash(data);
-            Console.WriteLine(ToHexString(hash));
+            Console.WriteLine(Convert.ToHexStringLower(hash));
         }
     }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-        {
-            hex.AppendFormat("{0:x2}", b);
-        }
-        return hex.ToString();
-    }
 }
diff --git a/bench/algorithm/mandelbrot/9.cs b/bench/algorithm/mandelbrot/9.cs
index 9409044b..bef1df20 100644
--- a/bench/algorithm/mandelbrot/9.cs
+++ b/bench/algorithm/mandelbrot/9.cs
@@ -83,17 +83,7 @@ public static unsafe void Main(string[] args)
             }
             using var hasher = MD5.Create();
             var hash = hasher.ComputeHash(data);
-            Console.WriteLine(ToHexString(hash));
+            Console.WriteLine(Convert.ToHexStringLower(hash));
         }
     }
-
-    static string ToHexString(byte[] ba)
-    {
-        StringBuilder hex = new StringBuilder(ba.Length * 2);
-        foreach (byte b in ba)
-        {
-            hex.AppendFormat("{0:x2}", b);
-        }
-        return hex.ToString();
-    }
 }