diff --git a/src/Mapster.Tests/WhenLookingUpHiddenMembers.cs b/src/Mapster.Tests/WhenLookingUpHiddenMembers.cs
new file mode 100644
index 00000000..8743296b
--- /dev/null
+++ b/src/Mapster.Tests/WhenLookingUpHiddenMembers.cs
@@ -0,0 +1,285 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using Shouldly;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Mapster.Tests
+{
+    [TestClass]
+    public class WhenLookingUpHiddenMembers
+    {
+        [TestMethod]
+        public void DropHiddenMembers_CurrentMembers_AreEnumeratedOnce()
+        {
+            var members = typeof(Source).GetProperties().Cast<MemberInfo>().ToArray();
+            var current = new CountingCollection(members);
+            var result = Filter(members, current);
+
+            current.Enumerations.ShouldBe(0);
+            using (result.GetEnumerator())
+                current.Enumerations.ShouldBe(0);
+            result.ToArray().ShouldBe(members);
+            current.Enumerations.ShouldBe(1);
+            result.ToArray().ShouldBe(members);
+            current.Enumerations.ShouldBe(2);
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_Source_IsEnumeratedOnce()
+        {
+            var members = typeof(Source).GetProperties().Cast<MemberInfo>().ToArray();
+            var visits = 0;
+            var source = members.Select(member =>
+            {
+                visits++;
+                return member;
+            });
+
+            var result = Filter(source, members);
+            visits.ShouldBe(0);
+            using (result.GetEnumerator())
+                visits.ShouldBe(0);
+            result.ToArray().ShouldBe(members);
+            visits.ShouldBe(members.Length);
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_PartialEnumeration_DoesNotTraverseRemainingSource()
+        {
+            var member = typeof(Source).GetProperty(nameof(Source.First));
+            var visits = 0;
+            var source = Enumerable.Repeat<MemberInfo>(member, 10).Select(item =>
+            {
+                visits++;
+                return item;
+            });
+
+            Filter(source, new[] { member }).First().ShouldBeSameAs(member);
+            visits.ShouldBe(1);
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_HiddenProperty_PreservesInheritedMembersAndOrder()
+        {
+            var inherited = typeof(BaseSource).GetProperty(nameof(BaseSource.Inherited));
+            var hidden = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var visible = typeof(DerivedSource).GetProperty(nameof(DerivedSource.Value), BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);
+            MemberInfo[] members = { inherited, hidden, visible, inherited };
+
+            Filter(members, new MemberInfo[] { visible }).ShouldBe(new MemberInfo[] { inherited, visible, inherited });
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_FieldHidesProperty_PreservesMetadataTokenSelection()
+        {
+            var hidden = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var visible = typeof(FieldSource).GetField(nameof(FieldSource.Value));
+
+            Filter(new MemberInfo[] { hidden, visible }, new MemberInfo[] { visible }).ShouldBe(new MemberInfo[] { visible });
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_DuplicateCurrentNames_FirstMemberWins()
+        {
+            var hidden = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var visible = typeof(DerivedSource).GetProperty(nameof(DerivedSource.Value), BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);
+
+            Filter(new MemberInfo[] { hidden, visible }, new MemberInfo[] { visible, hidden }).ShouldBe(new MemberInfo[] { visible });
+            Filter(new MemberInfo[] { hidden, visible }, new MemberInfo[] { hidden, visible }).ShouldBe(new MemberInfo[] { hidden });
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_DifferentlyCasedNames_AreDistinct()
+        {
+            var upper = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var lower = typeof(CaseSource).GetProperty(nameof(CaseSource.value));
+
+            Filter(new MemberInfo[] { upper, lower }, new MemberInfo[] { lower }).ShouldBe(new MemberInfo[] { upper, lower });
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_EmptyCurrentMembers_PreservesAllMembers()
+        {
+            MemberInfo[] members = typeof(BaseSource).GetProperties();
+
+            Filter(members, Array.Empty<MemberInfo>()).ShouldBe(members);
+            Filter(Array.Empty<MemberInfo>(), members).ShouldBeEmpty();
+            Filter(Array.Empty<MemberInfo>(), Array.Empty<MemberInfo>()).ShouldBeEmpty();
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_PrivateMemberHidesPublicMember_PreservesSelection()
+        {
+            var hidden = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var visible = typeof(PrivateSource).GetProperty("Value", BindingFlags.NonPublic | BindingFlags.Instance);
+
+            Filter(new MemberInfo[] { hidden }, new MemberInfo[] { visible }).ShouldBeEmpty();
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_ReenumeratedResult_RecomputesSelection()
+        {
+            var first = typeof(BaseSource).GetProperty(nameof(BaseSource.Value));
+            var second = typeof(DerivedSource).GetProperty(nameof(DerivedSource.Value), BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);
+            var current = new List<MemberInfo> { second };
+            var result = Filter(new MemberInfo[] { first, second }, current);
+
+            result.ToArray().ShouldBe(new MemberInfo[] { second });
+            current[0] = first;
+            result.ToArray().ShouldBe(new MemberInfo[] { first });
+        }
+
+        [TestMethod]
+        public void Adapt_HiddenProperty_UsesDerivedValueAndInheritedProperty()
+        {
+            var config = new TypeAdapterConfig();
+            config.NewConfig<DerivedSource, Destination>();
+            config.Compile();
+            var source = new DerivedSource { Value = "derived", Inherited = 42 };
+            ((BaseSource)source).Value = 7;
+
+            var result = source.Adapt<Destination>(config);
+            var target = source.Adapt(new Destination(), config);
+
+            result.Value.ShouldBe("derived");
+            result.Inherited.ShouldBe(42);
+            target.Value.ShouldBe("derived");
+            target.Inherited.ShouldBe(42);
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_PropertyHidesField_PreservesSelection()
+        {
+            var hidden = typeof(FieldSource).GetField(nameof(FieldSource.Value));
+            var visible = typeof(PropertySource).GetProperty(nameof(PropertySource.Value), BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly);
+
+            Filter(new MemberInfo[] { hidden, visible }, new MemberInfo[] { visible })
+                .ShouldBe(new MemberInfo[] { visible });
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_NameAccesses_GrowLinearly()
+        {
+            const int count = 64;
+            var members = Enumerable.Range(0, count)
+                .Select(index => new CountingMember("Member" + index, index)).ToArray();
+
+            Filter(members, members).ToArray().ShouldBe(members);
+
+            // Allow a constant number of name reads per member, but not a scan per match.
+            members.Sum(member => member.NameReads).ShouldBeLessThanOrEqualTo(8 * count);
+        }
+
+        [TestMethod]
+        public void DropHiddenMembers_UnmatchedCurrentMember_DoesNotReadMetadataToken()
+        {
+            var source = typeof(Source).GetProperty(nameof(Source.First));
+            var unmatched = new CountingMember("Unmatched");
+
+            Filter(new MemberInfo[] { source }, new MemberInfo[] { unmatched })
+                .ShouldBe(new MemberInfo[] { source });
+        }
+
+        private sealed class CountingMember : MemberInfo
+        {
+            private readonly string _name;
+            private readonly int? _token;
+
+            public CountingMember(string name, int? token = null)
+            {
+                _name = name;
+                _token = token;
+            }
+
+            public int NameReads { get; private set; }
+            public override string Name
+            {
+                get
+                {
+                    NameReads++;
+                    return _name;
+                }
+            }
+
+            public override int MetadataToken => _token ?? throw new InvalidOperationException("Unexpected token access");
+            public override Type DeclaringType => typeof(Source);
+            public override Type ReflectedType => typeof(Source);
+            public override MemberTypes MemberType => MemberTypes.Property;
+            public override object[] GetCustomAttributes(bool inherit) => throw new NotSupportedException();
+            public override object[] GetCustomAttributes(Type attributeType, bool inherit) => throw new NotSupportedException();
+            public override bool IsDefined(Type attributeType, bool inherit) => throw new NotSupportedException();
+        }
+
+        private static IEnumerable<MemberInfo> Filter(IEnumerable<MemberInfo> source, ICollection<MemberInfo> current)
+        {
+            return source.DropHiddenMembers(current);
+        }
+
+        private sealed class CountingCollection : ICollection<MemberInfo>
+        {
+            private readonly MemberInfo[] _members;
+            public CountingCollection(MemberInfo[] members) => _members = members;
+            public int Enumerations { get; private set; }
+            public int Count => _members.Length;
+            public bool IsReadOnly => true;
+            public IEnumerator<MemberInfo> GetEnumerator()
+            {
+                Enumerations++;
+                return ((IEnumerable<MemberInfo>)_members).GetEnumerator();
+            }
+            IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+            public bool Contains(MemberInfo item) => _members.Contains(item);
+            public void CopyTo(MemberInfo[] array, int index) => _members.CopyTo(array, index);
+            public void Add(MemberInfo item) => throw new NotSupportedException();
+            public void Clear() => throw new NotSupportedException();
+            public bool Remove(MemberInfo item) => throw new NotSupportedException();
+        }
+
+        public class BaseSource
+        {
+            public int Value { get; set; }
+            public int Inherited { get; set; }
+        }
+
+        public class DerivedSource : BaseSource
+        {
+            public new string Value { get; set; }
+        }
+
+        public class FieldSource : BaseSource
+        {
+            public new int Value;
+        }
+
+        public class CaseSource : BaseSource
+        {
+            public int value { get; set; }
+        }
+
+        public class PropertySource : FieldSource
+        {
+            public new string Value { get; set; }
+        }
+
+        public class PrivateSource : BaseSource
+        {
+            private new int Value { get; set; }
+        }
+
+        public class Destination
+        {
+            public string Value { get; set; }
+            public int Inherited { get; set; }
+        }
+
+        public class Source
+        {
+            public int First { get; set; }
+            public int Second { get; set; }
+            public int Third { get; set; }
+        }
+    }
+}
diff --git a/src/Mapster/Utils/ReflectionUtils.cs b/src/Mapster/Utils/ReflectionUtils.cs
index 8203858f..fe7bc6bd 100644
--- a/src/Mapster/Utils/ReflectionUtils.cs
+++ b/src/Mapster/Utils/ReflectionUtils.cs
@@ -80,35 +80,51 @@ public static IEnumerable<IMemberModelEx> GetFieldsAndProperties(this Type type,
                  BindingFlags.DeclaredOnly | BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,
                  (x, y) => true, type.FullName);
 
+            var firstMembersByName = CreateFirstMembersByName(currentTypeMembers);
+
             if (type.GetTypeInfo().IsInterface)
             {
                 var allInterfaces = GetAllInterfaces(type);
-                return allInterfaces.SelectMany(x => GetPropertiesFunc(x, currentTypeMembers));
+                return allInterfaces.SelectMany(GetPropertiesFunc);
             }
 
-            return GetPropertiesFunc(type, currentTypeMembers).Concat(GetFieldsFunc(type, currentTypeMembers));
+            return GetPropertiesFunc(type).Concat(GetFieldsFunc(type));
 
-            IEnumerable<IMemberModelEx> GetPropertiesFunc(Type t, MemberInfo[] currentTypeMembers) => t.GetProperties(bindingFlags)
-                .Where(x => x.GetIndexParameters().Length == 0).DropHiddenMembers(currentTypeMembers)
+            IEnumerable<IMemberModelEx> GetPropertiesFunc(Type t) => t.GetProperties(bindingFlags)
+                .Where(x => x.GetIndexParameters().Length == 0).DropHiddenMembers(firstMembersByName)
                 .Select(CreateModel);
 
-            IEnumerable<IMemberModelEx> GetFieldsFunc(Type t, MemberInfo[] overlapMembers) =>
-                t.GetFields(bindingFlags).DropHiddenMembers(overlapMembers)
+            IEnumerable<IMemberModelEx> GetFieldsFunc(Type t) =>
+                t.GetFields(bindingFlags).DropHiddenMembers(firstMembersByName)
                 .Select(CreateModel);
         }
 
         public static IEnumerable<T> DropHiddenMembers<T>(this IEnumerable<T> allMembers, ICollection<MemberInfo> currentTypeMembers) where T : MemberInfo
         {
-            var compareMemberNames = LinqCompat.IntersectBy(
-                allMembers,
-                currentTypeMembers.Select(x => x.Name),
-                x => x.Name).Select(x => x.Name);
+            var firstMembersByName = CreateFirstMembersByName(currentTypeMembers);
+            foreach (var member in allMembers.DropHiddenMembers(firstMembersByName))
+                yield return member;
+        }
 
+        private static Dictionary<string, MemberInfo> CreateFirstMembersByName(ICollection<MemberInfo> currentTypeMembers)
+        {
+            var firstMembersByName = new Dictionary<string, MemberInfo>(StringComparer.Ordinal);
+            foreach (var member in currentTypeMembers)
+            {
+                if (!firstMembersByName.ContainsKey(member.Name))
+                    firstMembersByName.Add(member.Name, member);
+            }
+
+            return firstMembersByName;
+        }
+
+        private static IEnumerable<T> DropHiddenMembers<T>(this IEnumerable<T> allMembers, Dictionary<string, MemberInfo> firstMembersByName) where T : MemberInfo
+        {
             foreach (var member in allMembers)
             {
-                if (compareMemberNames.Contains(member.Name))
+                if (firstMembersByName.TryGetValue(member.Name, out var currentMember))
                 {
-                    if (currentTypeMembers.First(x => x.Name == member.Name).MetadataToken == member.MetadataToken)
+                    if (currentMember.MetadataToken == member.MetadataToken)
                         yield return member;
                 }
                 else