使用带有 Linq.Dynamic 库的 DateDiff 来获取今天的记录

Using DateDiff with Linq.Dynamic library for fetching today records(使用带有 Linq.Dynamic 库的 DateDiff 来获取今天的记录)

问题描述

我正在尝试通过 MVC 5/Entity Framework 6 应用程序中的 Linq 表达式使用 DateDiff SQL 语法获取今天添加的所有记录.DateDiff 函数抛出运行时错误

I am trying to fetch all records added today using DateDiff SQL syntax via Linq expression in MVC 5 / Entity Framework 6 application. DateDiff function throw runtime error

其实我想用 linq 动态解析下面的 linq WHERE 子句

Actually i want to the following linq WHERE clause to parse with linq dynamics

.Where(p => DbFunctions.DiffDays(p.added_date, DateTime.Now) == 0)

为了获取今天添加的记录.我正在使用的示例代码如下所示

in order to fetch today added records. Sample code that i am using shown below

var _list = new vsk_error_log();
using (var entities = new vskdbEntities())
{
   _list = entities.vsk_error_log
  //.Where("DateDiff(DAY,added_date,getdate())=0")
  .Where(p => DbFunctions.DiffDays(p.added_date, DateTime.Now) == 0)
  .ToList();
}
return _list;

关于 Linq.Dynamic 表达式 - 如何编写 where 子句

Regarding Linq.Dynamic Expressions - how to write where clause

LINQ 中的动态 WHERE 子句

推荐答案

使用DbFunctions

.Where(p => DbFunctions.DiffDays(p.AddedDate, DateTime.Now) == 0)

如果您想动态调用它，您需要修改动态 LINQ 的代码.

If you want to invoke this dynamically, you'll need to modify code for the Dynamic LINQ.

1. 下载 包含 DynamicLibrary.cs 的示例项目.该文件位于 App_Code 文件夹下.
2. 找到 predefinedTypes 的静态定义并在最后添加 typeof(DbFunctions).

1. Download the sample project containing DynamicLibrary.cs. The file is located under App_Code folder.
2. Find the static definition for predefinedTypes and add typeof(DbFunctions) at the very end.

现在你可以这样做了:

.Where("DbFunctions.DiffDays(AddedDate, DateTime.Now) = 0")

它会被翻译成这个SQL:

And it will be translated to this SQL:

WHERE 0 = (DATEDIFF (day, [Extent1].[AddedDate], SysDateTime()))

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