如何在Entity Framework中的DbSet属性上设置过滤器选项？(How to set filter option on DbSet property in Entity Framework

如何在Entity Framework中的DbSet属性上设置过滤器选项？(How to set filter option on DbSet property in Entity Framework?)

我的上下文类中有一个DbSet属性，如下所示：

public class ProjectContext: DbContext { public ProjectContext(): base("name=DBCS") { } public DbSet<Employee> EmployeeDbSet { get; set; } }

此属性正在我的项目的许多地方使用。 现在我需要在Employee上设置一个通用条件，例如我只需要活跃的员工。 我可以通过简单地过滤我的linq查询来获得活跃的员工：

var employees = context.EmployeeDbSet.where(e => e.IsActive).ToList();

由于我已经在我的项目的许多地方编写了许多查询，现在我必须重写它们，这非常困难，耗时且容易出错。

由于这是一个通用条件，我想在所有查询上设置它，我正在寻找一种方法来设置EmployeeDbSet属性的条件。

可以完成吗？

谢谢你的帮助

I have a DbSet property in my context class as follows:

public class ProjectContext: DbContext { public ProjectContext(): base("name=DBCS") { } public DbSet<Employee> EmployeeDbSet { get; set; } }

This property is being used in many places of my project. Now I need to set a generic condition on Employee such as I need only active employees. I can get active employees by simply filtering my linq queries like this:

var employees = context.EmployeeDbSet.where(e => e.IsActive).ToList();

Since I've already written many queries in many places of my project, now I have to rewrite them all which is very difficult, time-consuming and error prone.

As this is a generic condition and I want to set this on all queries, I'm looking for a way to set the condition on EmployeeDbSet property instead.

Can it be accomplished?

Thanks for any help

最满意答案

您可以向DbContext添加IQueryable<Employee>属性，该属性返回活动where where条件集。

例;

public IQueryable<Employee> ActiveEmployees { get { return EmployeeDbSet.Where(e => e.IsActive); } }

通过这种方式，您可以将其与其他条件相结合;

context.ActiveEmployees.Where(x=> x.name == "john");

执行此操作后，您无法使用直接在DbSet<T>中声明的方法。 要在使用where之后使用find方法，您可以自己添加一个新的find方法，如下所示;

public static class DbModelExtensions { public static Employee Find(this IQueryable<Employee> query, int id) { return query.Where(x => x.Id == id).FirstOrDefault(); } }

如果在当前文件中引用其名称空间，则会添加一个扩展方法Find to only IQueryable<Employee> 。

然后就可以像这样使用它;

context.ActiveEmployees.Find(15);

You can add a IQueryable<Employee> property to your DbContext that returns the active where condition set.

Example;

public IQueryable<Employee> ActiveEmployees { get { return EmployeeDbSet.Where(e => e.IsActive); } }

This way you can combine it with other where conditions by just doing;

context.ActiveEmployees.Where(x=> x.name == "john");

After you do this you cant use methods that declared directly in DbSet<T>. To use find method after you use where, You can add a new find method yourself as follows;

public static class DbModelExtensions { public static Employee Find(this IQueryable<Employee> query, int id) { return query.Where(x => x.Id == id).FirstOrDefault(); } }

This adds a extension method Find to only IQueryable<Employee> if its namespace is referenced in current file.

Then you can use it like this;

context.ActiveEmployees.Find(15);