Quick fix Custom converter supporting from nullable ValueType

src/Mapster.Tests/WhenMappingNullablePrimitives.cs

@@ -158,8 +158,48 @@ public void MappingNullTuple()
             result.Application.ShouldBeNull();
         }
 
+        [TestMethod]
+        public void CustomConverterWorkWithNullablePrimitiveTypes()
+        {
+            TypeAdapterConfig config = new TypeAdapterConfig();
+            config.NewConfig<string?, bool?>().MapWith(src => Helper992.ParseToNullableBool(src));
+            config.Compile();
+
+            var src = new Source992 { Prop1 = "yes" };
+            var result = src.Adapt<Destination992>(config);
+
+            result.Prop1.ShouldBe(true);
+
+        }
+
+
         #region TestClasses
 
+        static class Helper992
+        {
+            public static bool? ParseToNullableBool(string? value)
+            {
+                if (string.IsNullOrWhiteSpace(value))
+                    return null;
+
+                return value.Trim().ToLower() switch
+                {
+                    "true" or "t" or "yes" or "1" => true,
+                    "false" or "f" or "no" or "0" => false,
+                    _ => null
+                };
+            }
+        }
+
+        public class Source992
+        {
+            public string? Prop1 { get; set; }
+        }
+
+        public class Destination992
+        {
+            public bool? Prop1 { get; set; }
+        }
 
         public class Output414
         {

src/Mapster/Adapters/NullableAdapter.cs

@@ -1,4 +1,5 @@
-using Mapster.Utils;
+using Mapster.Models;
+using Mapster.Utils;
 using System.Linq.Expressions;
 
 namespace Mapster.Adapters
@@ -19,6 +20,22 @@ protected override bool CanInline(Expression source, Expression? destination, Co
 
         protected override Expression? CreateInlineExpression(Expression source, CompileArgument arg, bool IsRequiredOnly = false)
         {
+            if (arg.ExplicitMapping)
+            {
+                LambdaExpression? Convert = null;
+
+                TypeAdapterRule? getsettings;
+                arg.Context.Config.RuleMap.TryGetValue(new TypeTuple(arg.SourceType, arg.DestinationType), out getsettings);
+
+                if (getsettings != null)
+                    if (arg.MapType == MapType.MapToTarget)
+                        Convert = getsettings.Settings.ConverterToTargetFactory(arg);
+                    else
+                        Convert = getsettings.Settings.ConverterFactory(arg);
+                if (Convert != null)
+                    return Convert.Apply(arg.MapType, source);
+            }
+
             var _source = source.Type.IsNullable() 
                 ? Expression.Convert(source, source.Type.GetGenericArguments()[0]) 
                 : source;