c# - 转换varchar值时转换失败

Question

当我尝试运行此命令时，它给我以下错误消息:

Conversion failed when converting the varchar value 'category_id' to data type int.

这是我的SQL和参数代码，我认为应该可以，但不能。

mycmd.CommandText="SELECT * FROM categories WHERE @db_property = @property_id"; 

// This contains a string "category_id", which is correct.
mycmd.Parameters.Add("@db_property", SqlDbType.VarChar).Value=db_property_field; 

// This contains an Int, referring to the category_id in database. As of now, this is 1
mycmd.Parameters.Add("@property_id", SqlDbType.Int).Value=property_id; 

在检查完这段代码后，我通过阅读器运行它，这就是上面显示错误消息的地方。一直问老师，和我类的优秀学生一样，没人能找到问题所在的线索。

Answer 1

您不应该添加字段名称作为参数。尝试更改您的脚本以包括实际的字段ID:

mycmd.CommandText = "SELECT * FROM categories WHERE category_id = @property_id";
mycmd.Parameters.Add("@property_id", SqlDbType.Int).Value = property_id;