update

code/src/Shared/Win.Sfs.Shared/Filter/FilterExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Text.Json;
@@ -77,6 +78,7 @@ namespace Win.Sfs.Shared.Filter
                 //var constant = Expression.Constant(filterCondition.Value);//创建常数
 
                 ConstantExpression constant = null;
+
                 if (filterCondition.Action != EnumFilterAction.In && filterCondition.Action != EnumFilterAction.NotIn)
                 {
                     constant = CreateConstantExpression(member.Type, filterCondition.Value);
@@ -150,12 +152,13 @@ namespace Win.Sfs.Shared.Filter
                 if (propertyType.IsGenericType &&
                     propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
                 {
-                    var objValue = Convert.ChangeType(value, propertyType.GetGenericArguments()[0]);
+                    var type = propertyType.GetGenericArguments()[0];
-                    constant = Expression.Constant(objValue);
+                    var objValue = type.IsEnum ? (Enum)Enum.Parse(type, value, true) : Convert.ChangeType(value, type);
+                    constant = Expression.Constant(new NullableConverter(propertyType).ConvertFrom(objValue));
                 }
                 else if (propertyType.IsEnum)
                 {
-                    var enumValue = (Enum)Enum.Parse(propertyType, value, true);
+                    var enumValue = (Enum?)Enum.Parse(propertyType, value, true);
                     constant = Expression.Constant(enumValue);
                 }
                 else
@@ -174,7 +177,11 @@ namespace Win.Sfs.Shared.Filter
 
             return constant;
         }
-
+        public static T? CreateNullable<T>(this T item) where T : struct
+        {
+            T? v = (T?)(new NullableConverter(typeof(T?))).ConvertFrom(item);
+            return v;
+        }
         private static Expression<Func<T, bool>> GetExpressionLikeMethod<T>(string methodName,
             FilterCondition filterCondition)
         {