如何从 SQL 服务器填充自定义类型列表<>

Question

我有一个名为 Author.cs 的 class 定义为：

public class Author : Interfaces.INode
{
    private List<INode> _targetList;
    private List<IAttribute> _attributeObject;

    // Author class Constructor
    public Author()
    {
        _targetList = new List<INode>();
    }
    //implementazion of _TargetObject INode method
    public List<INode> _TargetObject
    {
        get
        {
             return _targetList;
        }
    }
    //implementazion of _AttributeObject INode method
    public List<IAttribute> _AttributeObject
    {
        get
        {
             return _attributeObject;
        }
    }

    public int _aID { get; set; }
    public string _aName { get; set; }  
    // 'CoAuthor', 'Venue' and 'Paper' are classes that  
    // implements an interface i.e. `IAttribute`
    public List<CoAuthor> _aCoAuthors { get; set; } 
    public List<Venue> _aVenue { get; set; }
    public List<Paper> _aPapers { get; set; }
    public string _aArea { get; set; }
}

它在名为 Interfaces.INode.cs 的 Interfaces 文件夹中实现了一个接口，定义为：

public interface INode
{
    List<INode> _TargetObject { get; }
    List<IAttribute> _AttributeObject { get; }
}

public interface IAttribute : INode
{}

现在我想填写一个列表，即 List<Author> 即在另一个名为 AuthorCollector.cs

的 class 中

List<Author> _eAthors = new List<Author>();

我试过：

try
{
    SqlCommand _myCommand_1 = _con.CreateCommand();
    _myCommand_1.CommandText = @"SELECT Author_ID FROM M_DataFull  
                                 ORDER BY Author_ID, Year";
    var _AuthID = 0;
    int _Row_Counter = 0;

    using (SqlDataReader _myReader_1 = _myCommand_1.ExecuteReader())
    {
        while (_myReader_1.Read())
        {
            _Row_Counter++;
            _eAthors.Add(Convert.ToInt32(_myReader_1["Author_ID"]));
        }
        _myReader_1.Close();
     }
}
catch(Exception e)
{
     Console.WriteLine(e.Message);
}

错误是：

The best overloaded method match for _eAuthors.Add() has some invalid arguments.

Answer 1

您尝试将一个整数添加到作者列表中。伪代码：

_eAthors.Add(new Author(Convert.ToInt32(_myReader_1["Author_ID"])));

或

    _eAthors.Add(new Author(){_aID =Convert.ToInt32(_myReader_1["Author_ID"]}));

无论如何，我会为此使用 ORM 框架，例如 NHibernate 或 EntityFramework。这比自己做所有 SQL 映射要容易得多...

Answer 2

using (SqlDataReader _myReader_1 = _myCommand_1.ExecuteReader())
{
    while (_myReader_1.Read())
    {
       _Row_Counter++;
       Author author = new Author();
       author._aId = Convert.ToInt32(_myReader_1["Author_ID"]);
       author._aName = Convert.ToString(_myReader_1["Author_Name"]);
       //etc...
       _eAthors.Add(author);
    }
    _myReader_1.Close();
}

Answer 3

_eAthors 是 Authors 的集合，但代码试图添加一个 int 值，这在这种情况下会导致错误。

修改这一行

_eAthors.Add(Convert.ToInt32(_myReader_1["Author_ID"]))

到

_eAthors.Add(new Author
             {
                _aid= Convert.ToInt32(_myReader_1["Author_ID"]),  
                // add additional properties if you have one.                     
             });

如何从 SQL 服务器填充自定义类型列表<>

How to fill a custom typed List<> from SQL Server

c#

sql-server

list

class

user-defined