使用类将数据存储到列表中

Question

我有以下课程:

public class EmailData
{
    public string FirstName{ set; get; }
    public string LastName { set; get; }
    public string Location{ set; get; }
}

然后我做了以下但是没有正常工作:

List<EmailData> lstemail = new List<EmailData>(); 
lstemail.Add("JOhn","Smith","Los Angeles");

我收到一条消息,说没有方法的重载需要3个参数.

Answer 1

您需要添加该类的实例:

lstemail.Add(new EmailData { FirstName = "John", LastName = "Smith", Location = "Los Angeles"});

我建议在你的类中添加一个构造函数,但是:

public class EmailData
{
    public EmailData(string firstName, string lastName, string location)
    {
        this.FirstName = firstName;
        this.LastName = lastName;
        this.Location = location;
    }
    public string FirstName{ set; get; }
    public string LastName { set; get; }
    public string Location{ set; get; }
}

这将允许您使用构造函数将添加内容写入列表:

lstemail.Add(new EmailData("John", "Smith", "Los Angeles"));

Answer 2

如果要实例化并添加到同一行,则必须执行以下操作:

lstemail.Add(new EmailData { FirstName = "JOhn", LastName = "Smith", Location = "Los Angeles" });

或者只是事先实例化对象,并将其直接添加到:

EmailData data = new EmailData();
data.FirstName = "JOhn";
data.LastName = "Smith";
data.Location = "Los Angeles"

lstemail.Add(data);

Answer 3

您需要新建一个EmailData实例,然后添加:

var data = new EmailData { FirstName = "John", LastName = "Smith", Location = "LA" };

List<EmailData> listemail = new List<EmailData>();
listemail.Add(data);

如果你想做到:

listemail.Add("JOhn","Smith","Los Angeles");

您可以创建自己的自定义列表,通过专门化System.Collections.Generic.List并实现您自己的Add方法,或多或少像这样:

public class EmailList : List<EmailData>
{
    public void Add(string firstName, string lastName, string location)
    {
        var data = new EmailData 
                   { 
                       FirstName = firstName, 
                       LastName = lastName,
                       Location = location
                   };
        this.Add(data);
    }
}

Answer 4

一种方式(在一行中)是这样的:

listemail.Add(new EmailData {FirstName = "John", LastName = "Smith", Location = "Los Angeles"});

Answer 5

您需要创建要添加的类的实例:

lstemail.Add(new EmailData
                 {
                     FirstName = "JOhn",
                     LastName = "Smith",
                     Location = "Los Angeles"
                 });

请参见如何:使用对象初始化程序初始化对象(C#编程指南)

或者,您可以为EmailData对象声明构造函数并使用它来创建实例.

Answer 6

您没有在列表中添加该类的新实例.试试这个:

lstemail.Add(new EmailData { FirstName="John", LastName="Smith", Location="Los Angeles" });`

List是一个通用类.指定a时List<EmailData>,该Add方法期望一个类型为的对象EmailData.以更详细的语法表达的上述示例将是:

EmailData data = new EmailData();
data.FirstName="John";
data.LastName="Smith;
data.Location = "Los Angeles";
lstemail.Add(data);

Answer 7

你正试图打电话

列表<EmailData>.新增(字符串,字符串,字符串)

.试试这个:

lstemail.add(new EmailData{ FirstName="John", LastName="Smith", Location="Los Angeles"});

Answer 8

您如何期望List<EmailData>.Add知道如何将三个strings变成一个实例EmailData？你期待太多的框架.没有重载List<T>.Add需要三个字符串参数.事实上,唯一超载的List<T>.Add是T.因此,您必须创建一个实例EmailData并将其传递给List<T>.Add.这就是上面的代码所做的.

尝试:

lstemail.Add(new EmailData {
    FirstName = "JOhn", 
    LastName = "Smith",
    Location = "Los Angeles"
});

这使用C#对象初始化语法.或者,您可以向类中添加构造函数

public EmailData(string firstName, string lastName, string location) {
    this.FirstName = firstName;
    this.LastName = lastName;
    this.Location = location;
}

然后:

lstemail.Add(new EmailData("JOhn", "Smith", "Los Angeles"));

Answer 9

这行是你的问题:

lstemail.Add("JOhn","Smith","Los Angeles");

从3个字符串到您的自定义类没有直接强制转换.编译器无法弄清楚你要用这条线做什么.您需要Add()该类的实例lstemail:

lstemail.Add(new EmailData { FirstName = "JOhn", LastName = "Smith", Location = "Los Angeles" });

Answer 10

这是扩展方法版本:

public static class ListOfEmailDataExtension
{
    public static void Add(this List<EmailData> list, 
        string firstName, string lastName, string location)
    {
        if (null == list)
            throw new NullReferenceException();

        var emailData = new EmailData
                            {
                                FirstName = firstName, 
                                LastName = lastName, 
                                Location = location
                            };
        list.Add(emailData);
    }
}

用法:

List<EmailData> myList = new List<EmailData>();
myList.Add("Ron", "Klein", "Israel");