fix problem, when enum property has nullable type.

Author: cioxideru

src/SpatialFocus.EntityFrameworkCore.Extensions/EnumLookupExtension.cs

@@ -27,7 +27,7 @@ public static void ConfigureEnumLookup(this ModelBuilder modelBuilder, EnumLooku
 					continue;
 				}
 
-				if (enumOptions.UseEnumsWithAttributesOnly && !propertyType.GetCustomAttributes(typeof(EnumLookupAttribute), true).Any())
+				if (enumOptions.UseEnumsWithAttributesOnly && !propertyType.HasEnumWithAttribute())
 				{
 					continue;
 				}
@@ -43,7 +43,8 @@ public static void ConfigureEnumLookup(this ModelBuilder modelBuilder, EnumLooku
 				string tableName = enumOptions.NamingFunction(typeName);
 				enumLookupBuilder.ToTable(tableName);
 
-				string keyName = enumOptions.UseNumberLookup ? nameof(EnumWithNumberLookup<Enum>.Id)
+				string keyName = enumOptions.UseNumberLookup
+					? nameof(EnumWithNumberLookup<Enum>.Id)
 					: nameof(EnumWithStringLookup<Enum>.Id);
 
 				modelBuilder.Entity(entityType.Name).HasOne(concreteType).WithMany().HasPrincipalKey(keyName).HasForeignKey(property.Name);
@@ -108,6 +109,26 @@ private static Type GetEnumOrNullableEnumType(this Type propertyType)
 			return propertyType.IsEnum ? propertyType : propertyType.GetGenericArguments()[0];
 		}
 
+
+		private static bool HasEnumWithAttribute(this Type propertyType)
+		{
+
+			if (propertyType.GetCustomAttributes(typeof(EnumLookupAttribute), true).Any())
+			{
+				return true;
+			}
+
+			if (propertyType.IsGenericType && propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
+			{
+				if (propertyType.GetGenericArguments()[0].GetCustomAttributes(typeof(EnumLookupAttribute), true).Any())
+				{
+					return true;
+				}
+			}
+
+			return false;
+		}
+
 		private static bool IsEnumOrNullableEnumType(this Type propertyType)
 		{
 			if (propertyType.IsEnum)