实际使用中发现很多问题 如果用EFcore 框架，这个表达式树生成一个新的实体
导致EFcore 跟踪失败！
/// <summary>
/// 生成表达式目录树 泛型缓存
/// </summary>
/// <typeparam name="TIn"></typeparam>
/// <typeparam name="TOut"></typeparam>
public class ExpressionGenericMapper<TIn, TOut>//Mapper`2
{
private static Func<TIn, TOut> _FUNC = null;
private static Func<TIn, TOut, TOut> _FUNC2 = null;
public static TOut Trans(TIn t)
{
return _FUNC(t);
}
/// <summary>
/// 批量实体转换
/// </summary>
/// <param name="list">被转换的实体List</param>
/// <returns></returns>
public static List<TOut> TransList(List<TIn> list)
{
List<TOut> outs = new List<TOut>();
foreach (var item in list)
{
outs.Add(Trans(item));
}
return outs;
}
/// <summary>
/// 把TOut 按照TIn来更新
/// </summary>
/// <param name="news"></param>
/// <param name="old"></param>
/// <returns></returns>
public static TOut Modify(TIn news, TOut old)
{
return _FUNC2(news, old);
}
static ExpressionGenericMapper()
{
Type stringType = typeof(string);
#region 创建构造对象的委托
{
ParameterExpression parameterExpression = Expression.Parameter(typeof(TIn), "m");
List<MemberBinding> memberBindingList = new List<MemberBinding>();
foreach (var item in typeof(TOut).GetProperties())
{
var type = typeof(TIn);
if (item.PropertyType.IsClass && item.PropertyType != stringType)//排除String以外的引用类型，不进行赋值
{
continue;
}
var prop = type.GetProperty(item.GetMappingName());//从Out类找映射的字段名
if (prop != null)//如果TIn里能找到该属性
{
MemberExpression property = Expression.Property(parameterExpression, prop);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
}
foreach (var item in typeof(TOut).GetFields())
{
var type = typeof(TIn);
if (item.FieldType.IsClass && item.FieldType != stringType)//排除String以外的引用类型，不进行赋值
{
continue;
}
var prop = type.GetField(item.GetMappingName());//从Out类找映射的字段名
if (prop != null)
{
MemberExpression property = Expression.Field(parameterExpression, prop);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
}
MemberInitExpression memberInitExpression = Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList.ToArray());
Expression<Func<TIn, TOut>> lambda = Expression.Lambda<Func<TIn, TOut>>(memberInitExpression, new ParameterExpression[]
{
parameterExpression
});
_FUNC = lambda.Compile();//拼装是一次性的
}
#endregion
#region 修改对象的委托
{
ParameterExpression oExpression = Expression.Parameter(typeof(TOut), "o");
ParameterExpression nExpression = Expression.Parameter(typeof(TIn), "n");
List<MemberBinding> memberBindingList = new List<MemberBinding>();
foreach (var item in typeof(TOut).GetProperties())
{
var type = typeof(TIn);
if (item.PropertyType.IsClass && item.PropertyType != stringType)//排除String以外的引用类型，不进行赋值
{
continue;
}
var prop = type.GetProperty(item.GetMappingName());
if (prop != null)
{
MemberExpression property = Expression.Property(nExpression, prop);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
else
{
var propOld = typeof(TOut).GetProperty(item.Name);
MemberExpression property = Expression.Property(oExpression, propOld);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
}
foreach (var item in typeof(TOut).GetFields())
{
var type = typeof(TIn);
if (item.FieldType.IsClass && item.FieldType != stringType)//排除String以外的引用类型，不进行赋值
{
continue;
}
var prop = type.GetField(item.GetMappingName());
if (prop != null)
{
MemberExpression property = Expression.Field(nExpression, prop);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
else
{
var propOld = typeof(TOut).GetField(item.Name);
MemberExpression property = Expression.Field(oExpression, propOld);
MemberBinding memberBinding = Expression.Bind(item, property);
memberBindingList.Add(memberBinding);
}
}
MemberInitExpression memberInitExpression = Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList.ToArray());
Expression<Func<TIn, TOut, TOut>> lambda = Expression.Lambda<Func<TIn, TOut, TOut>>(memberInitExpression, new ParameterExpression[]
{
nExpression, oExpression
});
_FUNC2 = lambda.Compile();//拼装是一次性的
}
#endregion
}
}
public static class ExpressionGenericMapperExtend
{
public static string GetMappingName(this PropertyInfo prop)
{
if (prop.IsDefined(typeof(MappingAttribute), true))
{
MappingAttribute display = prop.GetCustomAttribute(typeof(MappingAttribute)) as MappingAttribute;
return display.MappingName;
}
return prop.Name;
}
public static string GetMappingName(this FieldInfo prop)
{
if (prop.IsDefined(typeof(MappingAttribute), true))
{
MappingAttribute display = prop.GetCustomAttribute(typeof(MappingAttribute)) as MappingAttribute;
return display.MappingName;
}
return prop.Name;
}
}
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class MappingAttribute : Attribute
{
public string MappingName;
public MappingAttribute(string _MappingName)
{
this.MappingName = _MappingName;
}
}
