diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/CachedSymbol.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/CachedSymbol.cs
index 5c72aa4d90e..8dd3694a715 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/CachedSymbol.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/CachedSymbol.cs
@@ -82,12 +82,12 @@ namespace Semmle.Extraction.CSharp.Entities
         /// The location which is stored in the database and is used when highlighting source code.
         /// It's generally short, e.g. a method name.
         /// </summary>
-        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Symbol.Locations.FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Symbol.Locations.BestOrDefault();
 
         /// <summary>
         /// The full text span of the entity, e.g. for binding comments.
         /// </summary>
-        public virtual Microsoft.CodeAnalysis.Location? FullLocation => Symbol.Locations.FirstOrDefault();
+        public virtual Microsoft.CodeAnalysis.Location? FullLocation => Symbol.Locations.BestOrDefault();
 
         public virtual IEnumerable<Extraction.Entities.Location> Locations
         {
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs
index 74c4c09c0f9..047a7b68ae6 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs
@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Conversion.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Conversion.cs
index eb6def9aebc..7fdd9168dca 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Conversion.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Conversion.cs
@@ -24,7 +24,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     .OfType<ConversionOperatorDeclarationSyntax>()
                     .Select(s => s.FixedLocation())
                     .Concat(Symbol.Locations)
-                    .FirstOrDefault();
+                    .BestOrDefault();
             }
         }
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Indexer.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Indexer.cs
index 1c41974a3a2..9ab2514918b 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Indexer.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Indexer.cs
@@ -93,7 +93,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     .OfType<IndexerDeclarationSyntax>()
                     .Select(s => s.GetLocation())
                     .Concat(Symbol.Locations)
-                    .First();
+                    .Best();
             }
         }
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Property.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Property.cs
index 07e74e82164..99f64e46c7b 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Property.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Property.cs
@@ -111,7 +111,7 @@ namespace Semmle.Extraction.CSharp.Entities
                     .OfType<PropertyDeclarationSyntax>()
                     .Select(s => s.GetLocation())
                     .Concat(Symbol.Locations)
-                    .First();
+                    .Best();
             }
         }
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs
index 791a1be3e45..5a840e3b9ef 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/DynamicType.cs
@@ -11,7 +11,7 @@ namespace Semmle.Extraction.CSharp.Entities
 
         public static DynamicType Create(Context cx, IDynamicTypeSymbol type) => DynamicTypeFactory.Instance.CreateEntityFromSymbol(cx, type);
 
-        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Context.Compilation.ObjectType.Locations.FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => Context.Compilation.ObjectType.Locations.BestOrDefault();
 
         public override void Populate(TextWriter trapFile)
         {
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs
index 5b8eb20bb1a..75a931e2266 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Entities/Types/NamedType.cs
@@ -124,7 +124,7 @@ namespace Semmle.Extraction.CSharp.Entities
                 );
         }
 
-        public override Microsoft.CodeAnalysis.Location? ReportingLocation => GetLocations(Symbol).FirstOrDefault();
+        public override Microsoft.CodeAnalysis.Location? ReportingLocation => GetLocations(Symbol).BestOrDefault();
 
         private bool IsAnonymousType() => Symbol.IsAnonymousType || Symbol.Name.Contains("__AnonymousType");
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Extractor/TracingAnalyser.cs b/csharp/extractor/Semmle.Extraction.CSharp/Extractor/TracingAnalyser.cs
index 417b45c37bb..cbed64db3a2 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Extractor/TracingAnalyser.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Extractor/TracingAnalyser.cs
@@ -130,7 +130,7 @@ namespace Semmle.Extraction.CSharp
                     return Path.ChangeExtension(entryPointFile, ".exe");
                 }
 
-                var entryPointFilename = entry.Locations.First().SourceTree!.FilePath;
+                var entryPointFilename = entry.Locations.Best().SourceTree!.FilePath;
                 return Path.ChangeExtension(entryPointFilename, ".exe");
             }
 
diff --git a/csharp/extractor/Semmle.Extraction.CSharp/Populators/Locations.cs b/csharp/extractor/Semmle.Extraction.CSharp/Populators/Locations.cs
index befeabba24e..885a19158eb 100644
--- a/csharp/extractor/Semmle.Extraction.CSharp/Populators/Locations.cs
+++ b/csharp/extractor/Semmle.Extraction.CSharp/Populators/Locations.cs
@@ -107,7 +107,7 @@ namespace Semmle.Extraction.CSharp.Populators
         {
             return symbol.DeclaringSyntaxReferences.Any() ?
                 symbol.DeclaringSyntaxReferences.First().GetSyntax().FixedLocation() :
-                symbol.Locations.First();
+                symbol.Locations.Best();
         }
     }
 }
diff --git a/csharp/extractor/Semmle.Extraction/Context.cs b/csharp/extractor/Semmle.Extraction/Context.cs
index c83a79fbddc..a1a43034c0c 100644
--- a/csharp/extractor/Semmle.Extraction/Context.cs
+++ b/csharp/extractor/Semmle.Extraction/Context.cs
@@ -379,7 +379,7 @@ namespace Semmle.Extraction
         {
             if (!(optionalSymbol is null))
             {
-                ExtractionError(message, optionalSymbol.ToDisplayString(), CreateLocation(optionalSymbol.Locations.FirstOrDefault()));
+                ExtractionError(message, optionalSymbol.ToDisplayString(), CreateLocation(optionalSymbol.Locations.BestOrDefault()));
             }
             else if (!(optionalEntity is null))
             {
diff --git a/csharp/extractor/Semmle.Extraction/InternalError.cs b/csharp/extractor/Semmle.Extraction/InternalError.cs
index 7ab8050bab6..f162316618e 100644
--- a/csharp/extractor/Semmle.Extraction/InternalError.cs
+++ b/csharp/extractor/Semmle.Extraction/InternalError.cs
@@ -13,7 +13,7 @@ namespace Semmle.Extraction
         {
             Text = msg;
             EntityText = symbol.ToString() ?? "";
-            Location = symbol.Locations.FirstOrDefault();
+            Location = symbol.Locations.BestOrDefault();
         }
 
         public InternalError(SyntaxNode node, string msg)
diff --git a/csharp/extractor/Semmle.Extraction/Message.cs b/csharp/extractor/Semmle.Extraction/Message.cs
index 34dd31d2ac4..7239c5880cb 100644
--- a/csharp/extractor/Semmle.Extraction/Message.cs
+++ b/csharp/extractor/Semmle.Extraction/Message.cs
@@ -27,7 +27,7 @@ namespace Semmle.Extraction
 
         public static Message Create(Context cx, string text, ISymbol symbol, string? stackTrace = null, Severity severity = Severity.Error)
         {
-            return new Message(text, symbol.ToString(), cx.CreateLocation(symbol.Locations.FirstOrDefault()), stackTrace, severity);
+            return new Message(text, symbol.ToString(), cx.CreateLocation(symbol.Locations.BestOrDefault()), stackTrace, severity);
         }
 
         public static Message Create(Context cx, string text, SyntaxNode node, string? stackTrace = null, Severity severity = Severity.Error)