Storing data into list with class

Question

I have the following class:

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

I then did the following but was not working properly:

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

I get a message that says no overload for method takes 3 arguments.

@Morpheus: Someone posts a question. What we see: `On your marks, get set, go!` — George Duckett, Dec 05 '11 at 21:14
@GeorgeDuckett just when i was about to type the answer i do a refresh pop 5 answers already! — Venki, Dec 05 '11 at 21:15
@Christopher Estep This is the 3rd question i missed out. I upvoted every answer because everyone responded in a jiffy — Venki, Dec 05 '11 at 21:18
@Christopher Yeah I down-voted because of the incorrect uppercase in "JOhn". — log0, Dec 05 '11 at 21:37
@Ugo You cost a guy reputation because of a sticky shift key? Wow, I thought *I* was pedantic! — Chris E, Dec 05 '11 at 21:46

score 87 · Answer 1 · answered Dec 05 '11 at 21:09

87

You need to add an instance of the class:

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

I would recommend adding a constructor to your class, however:

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; }
}

This would allow you to write the addition to your list using the constructor:

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

answered Dec 05 '11 at 21:09

Reed Copsey

554,122
78
1,158
1,373

I wouldn't recommend that at all! Why not simply use the Object Initialization syntax!?!?!? Unless you have logic in the constructor, or need to force certain parameters to be set, I wouldn't add a constructor. – John B Dec 09 '11 at 17:19
5

@JohnBubriski It's unlikely that there is a valid meaning for an `EmailData` class (in this instance) without a name or location. Using a default constructor would allow a user to inadvertently create a class that is in an invalid state. Whenever possible, it's ALWAYS a good idea to force constructors to include all required data to initialize the object into a meaningful state, as this will prevent errors from occurring over time. – Reed Copsey Dec 09 '11 at 17:27
@JohnBubriski Also for the cases where you want to make your objects immutable it's a way to avoid a public setter. – Roman Dec 12 '11 at 04:09
@R0MANARMY Sure, but that's a specific piece of functionality. – John B Dec 13 '11 at 13:19
@JohnBubriski Yes, it is. You asked why not use object initialization syntax, Reed and I gave you two reasons. Admittedly his is much better than mine. – Roman Dec 13 '11 at 14:26
Conversely, not having a default constructor means you can't select instances of EmailData with some LINQ queries. – Tetsujin no Oni Dec 14 '11 at 16:45
@TetsujinnoOni How so? This is not an issue with LINQ to Objects, but does require you to be explicit about using the constructor... – Reed Copsey Dec 14 '11 at 19:04

score 84 · Accepted Answer · answered Dec 05 '11 at 21:11

84

If you want to instantiate and add in the same line, you'd have to do something like this:

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

or just instantiate the object prior, and add it directly in:

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

lstemail.Add(data);

answered Dec 05 '11 at 21:11

slandau

23,528
42
122
184

1

How can I read the data from the list once I add some data into the list. Consider I have added three records. – Random User Jan 16 '14 at 06:44
Random user - add a foreach loop, and iterate over your list – GokuMizuno Apr 27 '19 at 12:19

Christian Horsdal · Answer 3 · 2013-11-11T10:47:00.310

You need to new up an instance of EmailData and then add that:

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

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

If you want to able to do:

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

you can create your own custom list, by specializing System.Collections.Generic.List and implementing your own Add method, more or less like this:

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);
    }
}

TheBoyan · Answer 4 · 2015-08-28T08:23:30.850

15

One way(in one line) to do it is like this:

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

edited Aug 28 '15 at 08:23

answered Dec 05 '11 at 21:10

TheBoyan

6,802
3
45
61

score 13 · Answer 5 · answered Dec 05 '11 at 21:09

You need to create an instance of the class to add:

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

See How to: Initialize Objects by Using an Object Initializer (C# Programming Guide)

Alternatively you could declare a constructor for you EmailData object and use that to create the instance.

score 8 · Answer 6 · answered Dec 05 '11 at 21:09

You're not adding a new instance of the class to the list. Try this:

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

List is a generic class. When you specify a List<EmailData>, the Add method is expecting an object that's of type EmailData. The example above, expressed in more verbose syntax, would be:

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

score 8 · Answer 7 · answered Dec 05 '11 at 21:10

8

You are attempting to call

List<EmailData>.Add(string,string,string)

. Try this:

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

answered Dec 05 '11 at 21:10

Tetsujin no Oni

7,300
2
29
46

score 6 · Answer 8 · answered Dec 05 '11 at 21:09

How do you expect List<EmailData>.Add to know how to turn three strings into an instance of EmailData? You're expecting too much of the Framework. There is no overload of List<T>.Add that takes in three string parameters. In fact, the only overload of List<T>.Add takes in a T. Therefore, you have to create an instance of EmailData and pass that to List<T>.Add. That is what the above code does.

Try:

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

This uses the C# object initialization syntax. Alternatively, you can add a constructor to your class

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

Then:

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

score 6 · Answer 9 · answered Dec 05 '11 at 21:09

6

This line is your problem:

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

There is no direct cast from 3 strings to your custom class. The compiler has no way of figuring out what you're trying to do with this line. You need to Add() an instance of the class to lstemail:

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

answered Dec 05 '11 at 21:09

David

208,112
36
198
279

The second line won't compile, either - need to specify the property names in an object initializer... – Reed Copsey Dec 05 '11 at 21:11
+0.5 Good explanation, but that's not how the C# object-initialization syntax works. See answers above. :) – Dan J Dec 05 '11 at 21:11
D'oh! That'll teach me to free-hand code without testing it :) – David Dec 05 '11 at 21:12

Ron Klein · Answer 10 · 2011-12-10T10:01:08.013

6

Here's the extension method version:

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);
    }
}

Usage:

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

edited Dec 10 '11 at 10:01

answered Dec 09 '11 at 09:46

Ron Klein

9,178
9
55
88

No need of the null check - list.Add will throw it anyway. – Sunny Milenov Dec 13 '11 at 14:49
@Sunny, I agree, but I still think it's a better practice to check for null value before executing additional code. – Ron Klein Dec 13 '11 at 20:08

score 2 · Answer 11 · answered Apr 04 '14 at 07:16

  public IEnumerable<CustInfo> SaveCustdata(CustInfo cust)
        {
            try
            {
                var customerinfo = new CustInfo
                {
                    Name = cust.Name,
                    AccountNo = cust.AccountNo,
                    Address = cust.Address
                };
                List<CustInfo> custlist = new List<CustInfo>();
                custlist.Add(customerinfo);
                return custlist;
            }
            catch (Exception)
            {
                return null;
            }
        }

score 2 · Answer 12 · answered Dec 13 '11 at 14:53

2

And if you want to create the list with some elements to start with:

var emailList = new List<EmailData>
{
   new EmailData { FirstName = "John", LastName = "Doe", Location = "Moscow" },
   new EmailData {.......}
};

answered Dec 13 '11 at 14:53

Sunny Milenov

21,990
6
80
106

score 0 · Answer 13 · answered Aug 26 '14 at 12:16

0

EmailData clsEmailData = new EmailData();
List<EmailData> lstemail = new List<EmailData>(); 

clsEmailData.FirstName="JOhn";
clsEmailData.LastName ="Smith";
clsEmailData.Location ="Los Angeles"

lstemail.add(clsEmailData);

answered Aug 26 '14 at 12:16

Mayank Pandey

185
1
11

Sorry because i didn't understand ur question meaning will u pls elaborate ur question so i can help? Thanks – Mayank Pandey Feb 05 '16 at 14:07

Storing data into list with class

13 Answers13

Linked