diff --git a/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextEncoder.cs b/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextEncoder.cs
index d2fdefe60d0dc..4d894dfb1e9af 100644
--- a/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextEncoder.cs
+++ b/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextEncoder.cs
@@ -4,7 +4,6 @@
 using System.IO;
 using System.Text;
 using System.Diagnostics;
-using System.Globalization;
 
 namespace System.Xml
 {
@@ -230,11 +229,11 @@ internal void Write(char[] array, int offset, int count)
 
         internal void WriteSurrogateCharEntity(char lowChar, char highChar)
         {
-            if (!XmlCharType.IsLowSurrogate(lowChar) ||
-                 !XmlCharType.IsHighSurrogate(highChar))
+            if (!XmlCharType.IsLowSurrogate(lowChar) || !XmlCharType.IsHighSurrogate(highChar))
             {
                 throw XmlConvert.CreateInvalidSurrogatePairException(lowChar, highChar);
             }
+
             int surrogateChar = XmlCharType.CombineSurrogateChar(lowChar, highChar);
 
             if (_cacheAttrValue)
@@ -244,9 +243,9 @@ internal void WriteSurrogateCharEntity(char lowChar, char highChar)
                 _attrValue.Append(lowChar);
             }
 
-            _textWriter.Write("&#x");
-            _textWriter.Write(surrogateChar.ToString("X", NumberFormatInfo.InvariantInfo));
-            _textWriter.Write(';');
+            Span<char> span = stackalloc char[12];
+            int charsWritten = WriteCharToSpan(span, surrogateChar);
+            _textWriter.Write(span.Slice(0, charsWritten));
         }
 
         internal void Write(ReadOnlySpan<char> text)
@@ -478,8 +477,6 @@ internal void WriteRaw(char[] array, int offset, int count)
             _textWriter.Write(array, offset, count);
         }
 
-
-
         internal void WriteCharEntity(char ch)
         {
             if (XmlCharType.IsSurrogate(ch))
@@ -487,16 +484,17 @@ internal void WriteCharEntity(char ch)
                 throw new ArgumentException(SR.Xml_InvalidSurrogateMissingLowChar);
             }
 
-            string strVal = ((int)ch).ToString("X", NumberFormatInfo.InvariantInfo);
+            Span<char> span = stackalloc char[12];
+            int charsWritten = WriteCharToSpan(span, ch);
+            ReadOnlySpan<char> ros = span.Slice(0, charsWritten);
+
             if (_cacheAttrValue)
             {
                 Debug.Assert(_attrValue != null);
-                _attrValue.Append("&#x");
-                _attrValue.Append(strVal);
-                _attrValue.Append(';');
+                _attrValue.Append(ros);
             }
 
-            WriteCharEntityImpl(strVal);
+            _textWriter.Write(ros);
         }
 
         internal void WriteEntityRef(string name)
@@ -518,14 +516,21 @@ internal void WriteEntityRef(string name)
 
         private void WriteCharEntityImpl(char ch)
         {
-            WriteCharEntityImpl(((int)ch).ToString("X", NumberFormatInfo.InvariantInfo));
+            Span<char> span = stackalloc char[12];
+            int charsWritten = WriteCharToSpan(span, ch);
+            _textWriter.Write(span.Slice(0, charsWritten));
         }
 
-        private void WriteCharEntityImpl(string strVal)
+        private static int WriteCharToSpan(Span<char> destination, int ch)
         {
-            _textWriter.Write("&#x");
-            _textWriter.Write(strVal);
-            _textWriter.Write(';');
+            Debug.Assert(destination.Length >= 12);
+            destination[0] = '&';
+            destination[1] = '#';
+            destination[2] = 'x';
+            ((uint)ch).TryFormat(destination.Slice(3), out int charsWritten, "X");
+            Debug.Assert(charsWritten != 0);
+            destination[charsWritten + 3] = ';';
+            return charsWritten;
         }
 
         private void WriteEntityRefImpl(string name)