diff --git a/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs b/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
index ea53e7db..1053b502 100644
--- a/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
+++ b/src/ConfigCatClient/Evaluation/RolloutEvaluator.cs
@@ -2,6 +2,7 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
+using System.Text;
 using ConfigCat.Client.Utils;
 using ConfigCat.Client.Versioning;
 
@@ -475,7 +476,7 @@ private static bool EvaluateSensitiveTextEquals(string text, string? comparisonV
     {
         EnsureComparisonValue(comparisonValue);
 
-        var hash = HashComparisonValue(text.AsSpan(), configJsonSalt, contextSalt);
+        var hash = HashComparisonValue(text, configJsonSalt, contextSalt);
 
         return hash.Equals(hexString: comparisonValue.AsSpan()) ^ negate;
     }
@@ -499,7 +500,7 @@ private static bool EvaluateSensitiveIsOneOf(string text, string[]? comparisonVa
     {
         EnsureComparisonValue(comparisonValues);
 
-        var hash = HashComparisonValue(text.AsSpan(), configJsonSalt, contextSalt);
+        var hash = HashComparisonValue(text, configJsonSalt, contextSalt);
 
         for (var i = 0; i < comparisonValues.Length; i++)
         {
@@ -540,6 +541,8 @@ private static bool EvaluateSensitiveTextSliceEqualsAnyOf(string text, string[]?
     {
         EnsureComparisonValue(comparisonValues);
 
+        var textUtf8Bytes = Encoding.UTF8.GetBytes(text);
+
         for (var i = 0; i < comparisonValues.Length; i++)
         {
             var item = EnsureComparisonValue(comparisonValues[i]);
@@ -555,12 +558,12 @@ private static bool EvaluateSensitiveTextSliceEqualsAnyOf(string text, string[]?
                 break; // execution should never get here (this is just for keeping the compiler happy)
             }
 
-            if (text.Length < sliceLength)
+            if (textUtf8Bytes.Length < sliceLength)
             {
                 continue;
             }
 
-            var slice = startsWith ? text.AsSpan(0, sliceLength) : text.AsSpan(text.Length - sliceLength);
+            var slice = startsWith ? textUtf8Bytes.AsSpan(0, sliceLength) : textUtf8Bytes.AsSpan(textUtf8Bytes.Length - sliceLength);
 
             var hash = HashComparisonValue(slice, configJsonSalt, contextSalt);
             if (hash.Equals(hexString: hash2))
@@ -693,7 +696,7 @@ private static bool EvaluateSensitiveArrayContainsAnyOf(string[] array, string[]
 
         for (var i = 0; i < array.Length; i++)
         {
-            var hash = HashComparisonValue(array[i].AsSpan(), configJsonSalt, contextSalt);
+            var hash = HashComparisonValue(array[i], configJsonSalt, contextSalt);
 
             for (var j = 0; j < comparisonValues.Length; j++)
             {
@@ -822,9 +825,32 @@ private bool EvaluateSegmentCondition(SegmentCondition condition, ref EvaluateCo
         return result;
     }
 
-    private static byte[] HashComparisonValue(ReadOnlySpan<char> value, string configJsonSalt, string contextSalt)
+    private static byte[] HashComparisonValue(ReadOnlySpan<byte> value, string configJsonSalt, string contextSalt)
+    {
+        var valueLength = value.Length;
+        var configJsonSaltLength = Encoding.UTF8.GetByteCount(configJsonSalt);
+        var contextSaltLength = Encoding.UTF8.GetByteCount(contextSalt);
+        var bytes = new byte[valueLength + configJsonSaltLength + contextSaltLength];
+
+        value.CopyTo(bytes);
+        Encoding.UTF8.GetBytes(configJsonSalt, 0, configJsonSalt.Length, bytes, valueLength);
+        Encoding.UTF8.GetBytes(contextSalt, 0, contextSalt.Length, bytes, valueLength + configJsonSaltLength);
+
+        return bytes.Sha256();
+    }
+
+    private static byte[] HashComparisonValue(string value, string configJsonSalt, string contextSalt)
     {
-        return string.Concat(value.ToConcatenable(), configJsonSalt, contextSalt).Sha256();
+        var valueLength = Encoding.UTF8.GetByteCount(value);
+        var configJsonSaltLength = Encoding.UTF8.GetByteCount(configJsonSalt);
+        var contextSaltLength = Encoding.UTF8.GetByteCount(contextSalt);
+        var bytes = new byte[valueLength + configJsonSaltLength + contextSaltLength];
+
+        Encoding.UTF8.GetBytes(value, 0, valueLength, bytes, 0);
+        Encoding.UTF8.GetBytes(configJsonSalt, 0, configJsonSalt.Length, bytes, valueLength);
+        Encoding.UTF8.GetBytes(contextSalt, 0, contextSalt.Length, bytes, valueLength + configJsonSaltLength);
+
+        return bytes.Sha256();
     }
 
     private static string EnsureConfigJsonSalt([NotNull] string? value)
diff --git a/src/ConfigCatClient/Extensions/StringExtensions.cs b/src/ConfigCatClient/Extensions/StringExtensions.cs
index 56f43ac7..27bc2461 100644
--- a/src/ConfigCatClient/Extensions/StringExtensions.cs
+++ b/src/ConfigCatClient/Extensions/StringExtensions.cs
@@ -16,29 +16,13 @@ public static byte[] Sha1(this string text)
 #endif
     }
 
-    public static byte[] Sha256(this string text)
+    public static byte[] Sha256(this byte[] bytes)
     {
-        var textBytes = Encoding.UTF8.GetBytes(text);
 #if NET5_0_OR_GREATER
-        return SHA256.HashData(textBytes);
+        return SHA256.HashData(bytes);
 #else
         using var hash = SHA256.Create();
-        return hash.ComputeHash(textBytes);
-#endif
-    }
-
-    public static
-#if NET5_0_OR_GREATER
-        ReadOnlySpan<char>
-#else
-        string
-#endif
-        ToConcatenable(this ReadOnlySpan<char> s)
-    {
-#if NET5_0_OR_GREATER
-        return s;
-#else
-        return s.ToString();
+        return hash.ComputeHash(bytes);
 #endif
     }