使用DapperExtensions进行谓词化(Predicate with DapperExtensions)

 我试图用DapperExtensions创建一个通用的Find方法 
 
 这是我的方法 
 
 public IEnumerable<T> Find(Expression<Func<T, object>> expression)
    {
        using (IDbConnection cn = GetCn())
        {
            cn.Open();

            var predicate = Predicates.Field<T>(expression, Operator.Eq, true);
            return cn.GetList<T>(predicate);
        }
    }
 
 但是我在这行上得到了System.NullReferenceException var predicate = Predicates.Field<T>(expression, Operator.Eq, true); 
 
 这是来自DapperExtensions帮助文档但我尝试将其转换为Generic方法。 
 
using (SqlConnection cn = new SqlConnection(_connectionString))
{
    cn.Open();
    var predicate = Predicates.Field<Person>(f => f.Active, Operator.Eq, true);
    IEnumerable<Person> list = cn.GetList<Person>(predicate);
    cn.Close();
}

Im trying to make a generic Find method with DapperExtensions
 
This is my method
 
 public IEnumerable<T> Find(Expression<Func<T, object>> expression)
    {
        using (IDbConnection cn = GetCn())
        {
            cn.Open();

            var predicate = Predicates.Field<T>(expression, Operator.Eq, true);
            return cn.GetList<T>(predicate);
        }
    }
 
But i get System.NullReferenceException on this row var predicate = Predicates.Field<T>(expression, Operator.Eq, true);
 
This is from the DapperExtensions help documentation But I try convert this to a Generic method.
 
using (SqlConnection cn = new SqlConnection(_connectionString))
{
    cn.Open();
    var predicate = Predicates.Field<Person>(f => f.Active, Operator.Eq, true);
    IEnumerable<Person> list = cn.GetList<Person>(predicate);
    cn.Close();
}

原文：https://stackoverflow.com/questions/14585212