C# 从列表中的所有项目中获取特定属性
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Get specific property from all items from the list
提问by inside
I have list of Contacts:
我有联系人列表：
public class Contact
{
private string _firstName;
private string _lastName;
private int _age;
/// <summary>
/// Constructor
/// </summary>
/// <param name="fname">Contact's First Name</param>
/// <param name="lname">Contact's Last Name</param>
/// <param name="age">Contact's Age</param>
public Contact(string fname, string lname, int age)
{
_firstName = fname;
_lastName = lname;
_age = age;
}
/// <summary>
/// Contact Last Name
/// </summary>
public string LastName
{
get
{
return _lastName;
}
set
{
_lastName = value;
}
}
/// <summary>
/// Contact First Name
/// </summary>
public string FirstName
{
get
{
return _firstName;
}
set
{
_firstName = value;
}
}
/// <summary>
/// Contact Age
/// </summary>
public int Age
{
get
{
return _age;
}
set
{
_age = value;
}
}
}
and here I am creating my list:
我在这里创建我的列表：
private List<Contact> _contactList;
_contactList = new List<Contact>();
_contactList.Add(new Contact("John", "Hymanson", 45));
_contactList.Add(new Contact("Hyman", "Doe", 20));
_contactList.Add(new Contact("Jassy", "Dol", 19));
_contactList.Add(new Contact("Sam", "Josin", 44));
Right now I am trying to get all the first names of all the contacts in separate list using LINQ.
现在我正在尝试使用 LINQ 在单独的列表中获取所有联系人的所有名字。
So far I tried:
到目前为止，我尝试过：
public List<string> FirstNames
{
get
{
return _contactList.Where(C => C.FirstName.ToList());
}
}
采纳答案by Mike Perrenoud
You want to use the Selectmethod, not Wherehere:
您想使用该Select方法，而不是Where在这里：
_contactList.Select(C => C.FirstName).ToList();
Further, the need for the ToList()only exists because the propertydemands it. You could return an IEnumerable<string>instead if you wanted to get rid of that.
此外，对ToList()唯一的需要是因为property需要它而存在。IEnumerable<string>如果你想摆脱它，你可以返回一个。
回答by Reda
public List<string> FirstNames
{
get
{
return _contactList.Select(C => C.FirstName).ToList();
}
}
