當設定.AsNoTracking()時，後續實體不會再更新，所以如果實體類中的導航實體中還包含實體，則無法附加到其中。

另外附加Expression Helper幫助類

using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using System.Linq;
using System.Text;
using TemplateNetCore.Framwork.Extensions;

namespace TemplateNetCore.Framwork.
 
Helpers
{
    public static class LambdaHelper
    {
        /// <summary>
        /// 建立lambda表示式：p=>true
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static Expression<Func<T, bool>> True
 
<T>()
        {
            return p => true;
        }

        /// <summary>
        /// 建立lambda表示式：p=>false
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static Expression<Func<T, bool
 
>> False<T>()
        {
            return p => false;
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TKey"></typeparam>
        /// <param name="sort"></param>
        /// <returns></returns>
        public static Expression<Func<T, TKey>> OrderExpression<T, TKey>(string propertyName)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");
            return Expression.Lambda<Func<T, TKey>>(Expression.Property(parameter, propertyName), parameter);
        }

        #region build selecter
        /// <summary>
        /// 建立lambda selecter：p=>{p.propertyName,p.propertyName1}
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TKey"></typeparam>
        /// <param name="Fields">欄位，‘,’隔開</param>
        /// <returns></returns>
        public static Expression<Func<TSource, T>> SelecterExpression<TSource, T>(string Fields) where TSource : class
        {
            ParameterExpression parameter = Expression.Parameter(typeof(TSource), "p");

            var tType = typeof(TSource);
            var props = tType.GetProperties();

            var dType = typeof(T);
            var dMembers = dType.GetMembers();
            List<MemberBinding> bindings = new List<MemberBinding>();

            foreach (string field in Fields.Split(',', StringSplitOptions.RemoveEmptyEntries))
            {
                if (props.Where(s => s.Name.ToUpper() == field.ToUpper()).Count() > 0)
                {
                    MemberExpression memberExpression = Expression.PropertyOrField(parameter, field);
                    bindings.Add(Expression.Bind(Array.Find(dMembers, m => m.Name.ToUpper() == field.ToUpper()), memberExpression));
                }
            }
            Expression body = Expression.MemberInit(Expression.New(dType), bindings);
            Expression<Func<TSource, T>> selector = (Expression<Func<TSource, T>>)Expression.Lambda(body, parameter);
            return selector;
        }

        /// <summary>
        /// 建立lambda selecter：p=>{p.propertyName,p.propertyName1} ，如果須要查詢子項如 x = a.b 或者 x = a.b.c
        /// </summary>
        /// <typeparam name="TSource"></typeparam>
        /// <typeparam name="TTarget"></typeparam>
        /// <param name="members"></param>
        /// <returns></returns>
        public static Expression<Func<TSource, TTarget>> BuildSelector<TSource, TTarget>(string members) => BuildSelector<TSource, TTarget>(members.Split(',').Select(m => m.Trim()));

        public static Expression<Func<TSource, TTarget>> BuildSelector<TSource, TTarget>(IEnumerable<string> members)
        {
            var parameter = Expression.Parameter(typeof(TSource), "e");
            var body = NewObject(typeof(TTarget), parameter, members.Select(m => m.Split('.')));
            return Expression.Lambda<Func<TSource, TTarget>>(body, parameter);
        }

        static Expression NewObject(Type targetType, Expression source, IEnumerable<string[]> memberPaths, int depth = 0)
        {
            var bindings = new List<MemberBinding>();
            var target = Expression.Constant(null, targetType);
            foreach (var memberGroup in memberPaths.GroupBy(path => path[depth]))
            {
                var memberName = memberGroup.Key;
                var targetMember = Expression.PropertyOrField(target, memberName);
                var sourceMember = Expression.PropertyOrField(source, memberName);
                var childMembers = memberGroup.Where(path => depth + 1 < path.Length);
                var targetValue = !childMembers.Any() ? sourceMember :
                    NewObject(targetMember.Type, sourceMember, childMembers, depth + 1);
                bindings.Add(Expression.Bind(targetMember.Member, targetValue));
            }
            return Expression.MemberInit(Expression.New(targetType), bindings);
        }
        #endregion

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName == propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> EqualExpression<T>(string propertyName, object propertyValue)
        {
            Type tProp = typeof(T).GetProperty(propertyName).PropertyType;

            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);

            ConstantExpression constant = null;
            if (tProp.FullName.Contains("Int"))
            {
                propertyValue = (int)propertyValue;
                if (tProp.FullName.Contains("Nullable"))
                {
                    constant = Expression.Constant(propertyValue, typeof(int?));
                }
            }
            else if (tProp.FullName.Contains("String"))
            {
                propertyValue = propertyValue.ToString();
                constant = Expression.Constant(propertyValue);
            }
            else if (tProp.FullName.Contains("DateTime"))
            {
                propertyValue = DateTime.Parse(propertyValue.ToString());
                if (tProp.FullName.Contains("Nullable"))
                {
                    constant = Expression.Constant(propertyValue, typeof(DateTime?));
                }
            }
            else
            {
                constant = Expression.Constant(propertyValue);
            }
            if (!tProp.FullName.Contains("Nullable"))
            {
                constant = Expression.Constant(propertyValue);
            }

            return Expression.Lambda<Func<T, bool>>(Expression.Equal(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName != propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="propertyName"></param>
        /// <param name="propertyValue"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> NotEqualExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            ConstantExpression constant = Expression.Constant(propertyValue);//建立常數
            return Expression.Lambda<Func<T, bool>>(Expression.NotEqual(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName > propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> GreaterThanExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            ConstantExpression constant = Expression.Constant(propertyValue);//建立常數
            return Expression.Lambda<Func<T, bool>>(Expression.GreaterThan(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName < propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> LessThanExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            ConstantExpression constant = Expression.Constant(propertyValue);//建立常數
            return Expression.Lambda<Func<T, bool>>(Expression.LessThan(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName >= propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> GreaterThanOrEqualExpression<T>(string propertyName, object propertyValue)
        {
            Type tProp = typeof(T).GetProperty(propertyName).PropertyType;

            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);

            ConstantExpression constant = null;
            if (tProp.FullName.Contains("Int"))
            {
                propertyValue = (int)propertyValue;
                if (tProp.FullName.Contains("Nullable"))
                {
                    constant = Expression.Constant(propertyValue, typeof(int?));
                }
            }
            else if (tProp.FullName.Contains("String"))
            {
                propertyValue = propertyValue.ToString();
                constant = Expression.Constant(propertyValue);
            }
            else if (tProp.FullName.Contains("DateTime"))
            {
                propertyValue = DateTime.Parse(propertyValue.ToString());
                if (tProp.FullName.Contains("Nullable"))
                {
                    constant = Expression.Constant(propertyValue, typeof(DateTime?));
                }
            }
            else
            {
                constant = Expression.Constant(propertyValue);
            }
            if (!tProp.FullName.Contains("Nullable"))
            {
                constant = Expression.Constant(propertyValue);
            }
            return Expression.Lambda<Func<T, bool>>(Expression.GreaterThanOrEqual(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName <= propertyValue
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> LessThanOrEqualExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");//建立引數p
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            ConstantExpression constant = Expression.Constant(propertyValue);//建立常數
            return Expression.Lambda<Func<T, bool>>(Expression.LessThanOrEqual(member, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：p=>p.propertyName.Contains(propertyValue)
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> ContainsExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
            ConstantExpression constant = Expression.Constant(propertyValue, typeof(string));
            return Expression.Lambda<Func<T, bool>>(Expression.Call(member, method, constant), parameter);
        }

        /// <summary>
        /// 建立lambda表示式：!(p=>p.propertyName.Contains(propertyValue))
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="column"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> NotContainsExpression<T>(string propertyName, object propertyValue)
        {
            ParameterExpression parameter = Expression.Parameter(typeof(T), "p");
            MemberExpression member = Expression.PropertyOrField(parameter, propertyName);
            MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
            ConstantExpression constant = Expression.Constant(propertyValue, typeof(string));
            return Expression.Lambda<Func<T, bool>>(Expression.Not(Expression.Call(member, method, constant)), parameter);
        }
    }
    public static class DataTypeHelper1
    {
        public static object ChanageType(this object value, Type convertsionType)
        {
            //判斷convertsionType型別是否為泛型，因為nullable是泛型類,
            if (convertsionType.IsGenericType &&
                //判斷convertsionType是否為nullable泛型類
                convertsionType.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
            {
                if (value == null || value.ToString().Length == 0)
                {
                    return null;
                }
                //如果convertsionType為nullable類，宣告一個NullableConverter類，該類提供從Nullable類到基礎基元型別的轉換
                System.ComponentModel.NullableConverter nullableConverter = new System.ComponentModel.NullableConverter(convertsionType);
                //將convertsionType轉換為nullable對的基礎基元型別
                convertsionType = nullableConverter.NullableType;
            }
            return Convert.ChangeType(value, convertsionType);
        }
    }


}