Question

我有一个客户对象类：

  public class customerObject
  {
    private string _address1;
    private string _address2;
    private string _address3;
    private string _category;
    private string _country;
    private string _county;
    private string _custcode;
    private string _fullname;
    private string _int_rep_hou;
    private string _int_rep_key;
    private double _lat;
    private double _lng;
    private string _postcode;
    private string _rep_code;
    private string _telephone;

    public customerObject()
    {
    }

    public string Address1
    {
        get { return _address1; }
        set { _address1 = value; }
    }

    public string Address2
    {
        get
        {
            return _address2;
        }

        set { _address2 = value; }
    }

    public string Address3 { get { return _address3; } set { _address3 = value; } }

    public string Category
    {
        get { return _category; }
        set { _category = value; }
    }

    public string Country { get { return _country; } set { _country = value; } }

    public string County { get { return _county; } set { _county = value; } }

    public string Custcode
    {
        get { return _custcode; }
        set { _custcode = value; }
    }

    public string Fullname
    {
        get { return _fullname; }
        set { _fullname = value; }
    }

    public string Int_rep_hou
    {
        get { return _int_rep_hou; }
        set { _int_rep_hou = value; }
    }

    public string Int_rep_key
    {
        get { return _int_rep_key; }
        set { _int_rep_key = value; }
    }

    public double Lat { get { return _lat; } set { _lat = value; } }

    public double Lng { get { return _lng; } set { _lng = value; } }

    public string Postcode { get { return _postcode; } set { _postcode = value; } }

    public string Rep_code
    {
        get { return _rep_code; }
        set { Rep_code = value; }
    }
    public string Telephone { get { return _telephone; } set { _telephone = value; } 

 }
}

我有一个CustomCollections类

public class CustomerCollection
{

    public List<customerObject> Customers { get; set; }


}

循环遍历dt行并转换为客户对象的方法

  public List<Valueobjects.CustomerCollection> dolist(DataTable temptablename)
    {
        //Create Collection Object
        Valueobjects.CustomerCollection Collection = new Valueobjects.CustomerCollection();

        foreach (DataRow row in temptablename.Rows)
        {
            //Create Customer Object
            Valueobjects.customerObject Customer = new Valueobjects.customerObject();

            //set values of customer object
            Customer.Rep_code = "";
            Customer.Int_rep_key = "";
            Customer.Int_rep_hou = "";
            Customer.Fullname = row["Fullname"].ToString().Trim();
            Customer.Custcode = row["Custcode"].ToString().Trim();
            Customer.Category = row["Category"].ToString().Trim();
            Customer.Address1 = row["Address1"].ToString().Trim();
            Customer.Address2 = row["Address2"].ToString().Trim();
            Customer.Address3 = row["Address3"].ToString().Trim();
            Customer.Postcode = row["Postcode"].ToString().Trim();
            Customer.Country = row["Country"].ToString().Trim();
            Customer.Telephone = row["Telephone"].ToString().Trim();
            Customer.Lat = Convert.ToDouble(row["Lat"]);
            Customer.Lng = Convert.ToDouble(row["Lng"]);
            Customer.County = row["County"].ToString().Trim();

            //add to the collection (list)
            Collection.Customers.Add(Customer);
        }

        temptablename = null;

        return Collection;
    }

但是，当我创建一个新的Customer对象和一个新的CustomerCollection对象时，我将客户添加到集合列表时收到错误。

错误：

错误32无法隐式转换类型 'Classes.Valueobjects.CustomerCollection'来 'System.Collections.Generic.List'

Answer 1

您的方法返回List<CustomerCollection>：

public List<Valueobjects.CustomerCollection> dolist(DataTable temptablename)
{
    //...
}

但是代码试图返回CustomerCollection：

return Collection;

正如错误所说，这两种类型是不同的。

如果CustomerCollection已经是客户的集合，那么在语义上什么是List<Valueobjects.CustomerCollection>？收藏品集合？看起来你过度多元化你的对象：）

这里有两种方法。从方法中返回CustomerCollection：

public CustomerCollection dolist(DataTable temptablename)
{
    //...
}

如果您想使用通用列表作为收集容器，请使用List<Customer>：

public List<Customer> dolist(DataTable temptablename)
{
    //...
    var Collection = new List<Customer>();
    //...
    Collection.Add(Customer);
    //...

    return Collection;
}

附注：您可能希望坚持使用C＃约定来进行变量命名。正如您在Stack Overflow上突出显示的代码中所看到的，您的变量名称很容易被误认为类/类型，这可能会在支持代码时引起混淆。

Answer 2

返回CustomerCollection而不是List<Valueobjects.CustomerCollection>：

public Valueobjects.CustomerCollection Dolist(DataTable temptablename)
{
// ...

您的对象有列表，不是列表。

MSDN：Inheritance

自定义集合/列表存储自定义对象

2 个答案: