“System.InvalidCastException"从SQL Server 2012 Express检索

本文关键字：Server SQL 2012 Express 检索 System InvalidCastException quot | 更新日期: 2023-09-27 18:03:48

我正在尝试测试一种方法，从SQL Server 2012 Express实例中检索一些信息并将其"添加"到列表中。问题是，当我试图运行测试时，我得到错误:

"系统。InvalidCastException "

代码如下:

List<Reference> lst = new List<Reference>();
//DB Connections is a class instance that takes care of the
//connection with the db.
DBConnections db = new DBConnections(DbConfig.conStr);
db.UpdateCmd("SELECT * FROM freelancers_references");
SqlDataReader dr = db.ExecuteReader();
if (dr.HasRows) {
    lst = dr.Cast<IDataRecord>().Select(r =>
        new Reference {
            Id = (int)dr["id"],
            OwnerId = (int)dr["owner_id"],
            Name = (string)dr["name"],
            Active = (bool)dr["active"]
        }).ToList<Reference>();
}
dr.Close();
return lst;

编辑:@Dan提供了一个可行的答案。虽然使用Convert.ToInt/ToString()等方法也能达到同样的效果

“System.InvalidCastException"从SQL Server 2012 Express检索

DBConnections db = new DBConnections(DbConfig.conStr);
db.UpdateCmd("SELECT * FROM freelancers_references");
SqlDataReader dr = db.ExecuteReader();
if (dr.HasRows) {
    lst = dr.OfType<IDataRecord>().Select(r =>
        new Reference {
            Id = (int)dr["id"],
            OwnerId = (int)dr["owner_id"],
            Name = (string)dr["name"],
            Active = (bool)dr["active"]
        }).ToList();
}
dr.Close();

检查columns是否允许为空。如果是，则使类型为空，即

OwnerId = (int?)dr["owner_id"],
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