bool type return rule in dapper

问题:

I use dapper ORM.So i use two rules Query & QuerySingle . Query return the list & QuerySingle return the single object.

So,I want to get a bool type.(Actually i wanted to get a bool is true or false record)

My Query

  public IEnumerable<T> Query<T>(string SqlString) where T : class
    {
        return this.conn.Query<T>(SqlString);
    }

So,How can i write bool type return ?

回答1:

So, I want to get a bool type. (Actually I wanted to get a bool is true or false record)

You can write a method like this:

public bool GetBooleanValue(string sql)
{
    return the_connection.Query<bool>(sql).FirstOrDefault();
}

The beauty about the FirstOrDefault is that when your query returns an empty row, Dapper will give you false. That suggested code will work as long as your query returns a value that can be translated into a boolean by your data provider. In case of SQL Server you would get:

• TRUE for GetBooleanValue("select 1");
• FALSE for GetBooleanValue("select 0");

where 1 and 0 are values from a table column of boolean type.

You can even use the code if you want to test if something exists or a group of values exists something like GetBooleanValue("select COUNT(*) from the_table where the_column='some_filter'").