用于从不同表中获取记录的通用查询 [英] Generic query to get records from different tables

问题描述

在我们的项目中，我们使用Linq-to-Entities连接到数据库。要读取有效记录，比方说，table1有方法：

In our project we connecting to database with Linq-to-Entities. To read valid records from ,let's say, table1 there is method:

public List<tableName> GetTableNameRecords()
{
    try
    {
        return (from x in _context.tableName
                          where x.valid == 1
                          select x).ToList();
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }
}

它有效，但有问题 - 我们需要为每个表编写相同的查询，只更改表名。有没有办法编写通用方法，我们只能传递表名？类似于：

It works, but there is a problem - for each table we need to write the same query and only change table name. Is there a way to write generic method where we could only pass table name? Something like:

public List<T> GetRecords<T>()
{
    try
    {
        return (from x in _context.<T>
                          where x.valid == 1
                          select x).ToList();
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }
}

推荐答案

You can use reflection for this, but you're facing some rather ugly code. However, if you're willing to change your models a little bit, you can do that in a relatively straightforward way.

Create an interface that has one property - valid, like so:

interface IValid
{
    bool valid { get; set; }
}

Make sure all your models that have this valid field implement the interface. Then you can do something like this:

List<T> GetValid<T>(DbContext context) where T: IValid
{
    return context.Set<T>().Where(x=>x.valid).ToList()
}

By having your models implement the interface, you can use an ordinary LINQ expression and have the compiler sort everything out

。

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