diff --git a/src/DocumentFormat.OpenXml.Framework/EnumerableExtensions.cs b/src/DocumentFormat.OpenXml.Framework/EnumerableExtensions.cs
deleted file mode 100644
index c13d46d06..000000000
--- a/src/DocumentFormat.OpenXml.Framework/EnumerableExtensions.cs
+++ /dev/null
@@ -1,33 +0,0 @@
-// Copyright (c) Microsoft. All rights reserved.
-// Licensed under the MIT license. See LICENSE file in the project root for full license information.
-
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace DocumentFormat.OpenXml;
-
-internal static class EnumerableExtensions
-{
-    /// <summary>
-    /// Similar to <see cref="Enumerable.FirstOrDefault{TSource}(IEnumerable{TSource})"/> but will also verify that at most there is one.
-    /// </summary>
-    public static T? FirstOrDefaultAndMaxOne<T>(this IEnumerable<T> enumerable, Func<Exception>? exceptionFactory = null)
-    {
-        using var e = enumerable.GetEnumerator();
-
-        if (e.MoveNext())
-        {
-            var first = e.Current;
-
-            if (e.MoveNext())
-            {
-                throw exceptionFactory?.Invoke() ?? throw new InvalidOperationException(ExceptionMessages.FirstOrDefaultMaxOne);
-            }
-
-            return first;
-        }
-
-        return default;
-    }
-}
diff --git a/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.Designer.cs b/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.Designer.cs
index cf1eaed38..8419ed6c2 100644
--- a/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.Designer.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.Designer.cs
@@ -330,15 +330,6 @@ internal static string FileNotFound {
             }
         }
         
-        /// <summary>
-        ///   Looks up a localized string similar to The enumerable contained more than a single element when only zero or one are allowed..
-        /// </summary>
-        internal static string FirstOrDefaultMaxOne {
-            get {
-                return ResourceManager.GetString("FirstOrDefaultMaxOne", resourceCulture);
-            }
-        }
-        
         /// <summary>
         ///   Looks up a localized string similar to The root XML element &quot;{0}&quot; in the part is incorrect. The expected root XML element is: &quot;{1}&quot;..
         /// </summary>
diff --git a/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.resx b/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.resx
index b0aaa58a4..171275b81 100644
--- a/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.resx
+++ b/src/DocumentFormat.OpenXml.Framework/Resources/ExceptionMessages.resx
@@ -117,9 +117,6 @@
   <resheader name="writer">
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
-  <data name="AddedPartIsNotAllowed" xml:space="preserve">
-    <value>The part cannot be added here.</value>
-  </data>
   <data name="CannotChangeDocumentType" xml:space="preserve">
     <value>Cannot change the document type.</value>
   </data>
@@ -411,7 +408,7 @@
   <data name="FailedToOpenPackage" xml:space="preserve">
     <value>Package could not be opened for stream. See inner exception for details and be aware that there are behavior differences in stream support between .NET Framework and Core.</value>
   </data>
-  <data name="FirstOrDefaultMaxOne" xml:space="preserve">
-    <value>The enumerable contained more than a single element when only zero or one are allowed.</value>
+  <data name="AddedPartIsNotAllowed" xml:space="preserve">
+    <value>The part cannot be added here.</value>
   </data>
 </root>
\ No newline at end of file
diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/RelationshipTypeConstraint.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/RelationshipTypeConstraint.cs
index 2e04de7dc..dd0efffbc 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/RelationshipTypeConstraint.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/RelationshipTypeConstraint.cs
@@ -64,7 +64,7 @@ public RelationshipTypeConstraint(OpenXmlQualifiedName attribute, string type)
             {
                 var pair = current.Part.Parts
                     .Where(p => p.RelationshipId == attribute.Value.InnerText)
-                    .FirstOrDefaultAndMaxOne();
+                    .SingleOrDefault();
 
                 if (pair is { })
                 {
diff --git a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/SemanticConstraint.cs b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/SemanticConstraint.cs
index 6793e17ec..4ce094d37 100644
--- a/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/SemanticConstraint.cs
+++ b/src/DocumentFormat.OpenXml.Framework/Validation/Semantic/SemanticConstraint.cs
@@ -241,6 +241,7 @@ protected static bool GetAttrNumVal(OpenXmlSimpleType attributeValue, out double
                 CultureInfo.InvariantCulture, out value);
         }
 
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Performance", "CA1851:Possible multiple enumerations of 'IEnumerable' collection", Justification = "We're resetting the parts variable, but the analyzer doesn't realize that")]
         private static OpenXmlPart? GetPartThroughPartPath(IEnumerable<IdPartPair> pairs, string[] path)
         {
             var foundPart = default(OpenXmlPart);
@@ -251,7 +252,7 @@ protected static bool GetAttrNumVal(OpenXmlSimpleType attributeValue, out double
                 foundPart = parts
                     .Where(p => p.OpenXmlPart.GetType().Name == path[i])
                     .Select(t => t.OpenXmlPart)
-                    .FirstOrDefaultAndMaxOne(static () => new System.IO.FileFormatException(ValidationResources.MoreThanOnePartForOneUri));
+                    .SingleOrDefault();
 
                 if (foundPart is not { })
                 {