[英]Convert string to Func<T,Object>
我有以下方法
public List<ServicesLogModel> Paging(Func<ServicesLogModel, bool> condition, string columnOrder, bool? orderDescending, int? pageIndex, int? pageSize, out int total)
{
return _mongoRepository.Paging(condition, order => order.Message, orderDescending.Value, pageIndex.Value, pageSize.Value, out total);
}
columnOrder
參數是一個字符串作為 lambda 表達式(例如: order => order.Message
),我必須將其轉換為Func<T, object>
我正在嘗試Expression.Parameter
var parm = Expression.Parameter(typeof(ServicesLogModel), "order");
var propName = Expression.Property(parm, columnOrder);
Expression predicateBody = Expression.Assign(parm, propName);
var test=Expression.Lambda<Func<ServicesLogModel, object>>(predicateBody, parm);
它不起作用錯誤:您不能使用“System.String”類型的表達式來分配“ServicesLogModel”類型
編輯:方法簽名
public List<T> Paging(Func<T, bool> condition, Func<T, object> order, bool orderDescending, int pageIndex, int pageSize,out int total)
調用方法
[HttpGet]
[Route("Admin/GetReaderConnectorLog/{Apikey}/{SecretKey}/{index}/{pagesize}/{orderAsc}/{columnOrder}")]
public IActionResult GetReaderConnectorLog(string Apikey, string SecretKey, int? index, int? pagesize, bool? orderAsc, string columnOrder)
{
try
{
_userService.BeginTransaction();
// _webApiHelper.ValidateApiKey(Apikey, SecretKey, Context, _userService, true);
int total;
//TEST
var listModel = _connectorLogService.Paging(_ => true, $"order => order.{columnOrder}", orderAsc, index, pagesize, out total);
_userService.Commit();
return _webApiHelper.OkResponse($"{_appSettings.Options.UserTag}[Send List User]", Context, new PaginationModel<ServicesLogModel> { ListData = listModel, Total = total, Apikey = Apikey, SecretKey = SecretKey });
}
catch (Exception e)
{
_userService.Rollback();
return _webApiHelper.ResolveException(Context, e);
}
}
問候
嗯,最終的解決方案是這樣的
public Func<T, object> GetLambda<T>(string property)
{
var param = Expression.Parameter(typeof(T), "p");
Expression parent = Expression.Property(param, property);
if (!parent.Type.IsValueType)
{
return Expression.Lambda<Func<T, object>>(parent, param).Compile();
}
var convert = Expression.Convert(parent, typeof(object));
return Expression.Lambda<Func<T, object>>(convert, param).Compile();
}
由於您的方法需要Func<T,object>
而不是Expression<Func<T,object>>
,一個簡單的解決方案是使用反射:
public Func<T, object> GetPropertyFunc<T>(string property_name)
{
return t => typeof (T).GetProperty(property_name).GetMethod.Invoke(t, new object[] {});
}
此方法采用屬性的名稱,並返回所需的函數。
這是您可以測試它的方法:
ServicesLogModel model = new ServicesLogModel()
{
Message = "my message"
};
Func<ServicesLogModel, object> func = GetPropertyFunc < ServicesLogModel>("Message"); //I am assuming the property name is "Message", but you can pass any string here
var message = func(model) as string;
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