diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToNonValue.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToNonValue.cs
index a7639eb1d..74bf90d85 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToNonValue.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToNonValue.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using DocumentFormat.OpenXml.Framework;
+using System.Text;
 
 namespace DocumentFormat.OpenXml.Validation.Semantic
 {
@@ -59,17 +60,20 @@ public AttributeAbsentConditionToNonValue(OpenXmlQualifiedName absentAttribute,
                 }
             }
 
-            string valueString = "'" + _values[0] + "'";
+            var sb = new StringBuilder();
+            sb.Append('\'').Append(_values[0]).Append('\'');
             if (_values.Length > 1)
             {
                 for (int i = 1; i < _values.Length - 1; i++)
                 {
-                    valueString += ", '" + _values[i] + "'";
+                    sb.Append(", '").Append(_values[i]).Append('\'');
                 }
 
-                valueString += " and '" + _values[_values.Length - 1] + "'";
+                sb.Append(" and '").Append(_values[_values.Length - 1]).Append('\'');
             }
 
+            string valueString = sb.ToString();
+
             return new ValidationErrorInfo()
             {
                 Id = "Sem_AttributeAbsentConditionToNonValue",
diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToValue.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToValue.cs
index d4221913a..0bd5f3c0d 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToValue.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeAbsentConditionToValue.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using DocumentFormat.OpenXml.Framework;
+using System.Text;
 
 namespace DocumentFormat.OpenXml.Validation.Semantic
 {
@@ -55,17 +56,20 @@ public AttributeAbsentConditionToValue(OpenXmlQualifiedName absentAttribute, Ope
             {
                 if (AttributeValueEquals(conditionAttribute.Value, value, false))
                 {
-                    string valueString = "'" + _values[0] + "'";
+                    var sb = new StringBuilder();
+                    sb.Append('\'').Append(_values[0]).Append('\'');
                     if (_values.Length > 1)
                     {
                         for (int i = 1; i < _values.Length - 1; i++)
                         {
-                            valueString += ", '" + _values[i] + "'";
+                            sb.Append(", '").Append(_values[i]).Append('\'');
                         }
 
-                        valueString += " or '" + _values[_values.Length - 1] + "'";
+                        sb.Append(" or '").Append(_values[_values.Length - 1]).Append('\'');
                     }
 
+                    string valueString = sb.ToString();
+
                     return new ValidationErrorInfo()
                     {
                         Id = "Sem_AttributeAbsentConditionToValue",
diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeMutualExclusive.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeMutualExclusive.cs
index 1197ee40f..8ad401a7c 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeMutualExclusive.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeMutualExclusive.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using DocumentFormat.OpenXml.Framework;
+using System.Text;
 
 namespace DocumentFormat.OpenXml.Validation.Semantic
 {
@@ -57,13 +58,18 @@ private AttributeMutualExclusive(OpenXmlQualifiedName[] attributes)
                 return null;
             }
 
-            var attributes = string.Empty;
-            var existAttribute = string.Empty;
-            var existAttribute2 = string.Empty;
+            var attributesSb = new StringBuilder();
+            var existAttributeSb = new StringBuilder();
+            string? existAttribute2 = null;
 
             foreach (var attribute in _attributes)
             {
-                attributes += "," + attribute;
+                if (attributesSb.Length > 0)
+                {
+                    attributesSb.Append(',');
+                }
+
+                attributesSb.Append(attribute);
 
                 if (!TryFindAttribute(element, attribute, out var found))
                 {
@@ -72,16 +78,21 @@ private AttributeMutualExclusive(OpenXmlQualifiedName[] attributes)
 
                 if (found.Value is not null)
                 {
-                    if (!string.IsNullOrEmpty(existAttribute2))
+                    if (existAttribute2 is not null)
                     {
-                        existAttribute += "," + existAttribute2;
+                        if (existAttributeSb.Length > 0)
+                        {
+                            existAttributeSb.Append(',');
+                        }
+
+                        existAttributeSb.Append(existAttribute2);
                     }
 
                     existAttribute2 = found.ToString();
                 }
             }
 
-            if (string.IsNullOrEmpty(existAttribute))
+            if (existAttributeSb.Length == 0)
             {
                 return null;
             }
@@ -93,9 +104,9 @@ private AttributeMutualExclusive(OpenXmlQualifiedName[] attributes)
                 Node = element,
                 Description = SR.Format(
                     ValidationResources.Sem_AttributeMutualExclusive,
-                    existAttribute.Substring(1),
+                    existAttributeSb.ToString(),
                     existAttribute2,
-                    attributes.Substring(1)),
+                    attributesSb.ToString()),
             };
         }
     }
diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeValueConditionToAnother.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeValueConditionToAnother.cs
index e1380a2cc..37744f78f 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeValueConditionToAnother.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/AttributeValueConditionToAnother.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using DocumentFormat.OpenXml.Framework;
+using System.Text;
 
 namespace DocumentFormat.OpenXml.Validation.Semantic
 {
@@ -65,28 +66,34 @@ public AttributeValueConditionToAnother(OpenXmlQualifiedName attribute, OpenXmlQ
             {
                 if (AttributeValueEquals(conditionAttribute.Value, value, false))
                 {
-                    string attributeValueString = "'" + _values[0] + "'";
+                    var sb = new StringBuilder();
+                    sb.Append('\'').Append(_values[0]).Append('\'');
                     if (_values.Length > 1)
                     {
                         for (int i = 1; i < _values.Length - 1; i++)
                         {
-                            attributeValueString += ", '" + _values[i] + "'";
+                            sb.Append(", '").Append(_values[i]).Append('\'');
                         }
 
-                        attributeValueString += " or '" + _values[_values.Length - 1] + "'";
+                        sb.Append(" or '").Append(_values[_values.Length - 1]).Append('\'');
                     }
 
-                    string otherAttributeValueString = "'" + _otherValues[0] + "'";
+                    string attributeValueString = sb.ToString();
+
+                    var otherSb = new StringBuilder();
+                    otherSb.Append('\'').Append(_otherValues[0]).Append('\'');
                     if (_otherValues.Length > 1)
                     {
                         for (int i = 1; i < _otherValues.Length - 1; i++)
                         {
-                            otherAttributeValueString += ", '" + _otherValues[i] + "'";
+                            otherSb.Append(", '").Append(_otherValues[i]).Append('\'');
                         }
 
-                        otherAttributeValueString += " or '" + _otherValues[_otherValues.Length - 1] + "'";
+                        otherSb.Append(" or '").Append(_otherValues[_otherValues.Length - 1]).Append('\'');
                     }
 
+                    string otherAttributeValueString = otherSb.ToString();
+
                     return new ValidationErrorInfo()
                     {
                         Id = "Sem_AttributeValueConditionToAnother",