C# ASP.NET - No overload for method 'Add' takes 1 arguments

Question

I have this function below, what I am trying to do, is connect to the database, run a query and put the results in a List and then return the list. This is what I came up so far,

 public class AirportClass
    {
        private string connectionString;
        private SqlConnection connection;
        private SqlCommand command;
        private Dictionary<string, List<string>> items;

        public AirportClass()
        {
            connectionString = @"Server=server;database=database;uid=username;pwd=password;";
        }

        public Dictionary<string, List<string>> getListItems()
        {
            items = new Dictionary<string, List<string>>();
            connection = new SqlConnection(connectionString);
            command = new SqlCommand("SELECT * FROM Table");
            command.Connection = connection;
            connection.Open();
            SqlDataReader dataReader = command.ExecuteReader();
            while (dataReader.Read())
            {
                string data = dataReader[0].ToString();
                items.Add(data);
            }
            connection.Close();
            return items;
        }
    }

I have ran the debugger and I can see that I am getting a connection and data is getting returned, I am just have trouble putting the items into a list. I get error when I add the items.Add(data) saying No overload for method 'Add' takes 1 arguments....can anyone help me out please?

Just [check](http://msdn.microsoft.com/en-us/library/k7z0zy8k(v=vs.110).aspx) `Dictionary.Add` syntax. — mazharenko, Aug 07 '14 at 13:24
Why are you using `Dictionary`? Use `List` instead. `Dictionary` is used to store `key => value` data. — Kamil T, Aug 07 '14 at 13:24
Anyway, I can't understand why IDE lets you to debug. It mustn't compile — mazharenko, Aug 07 '14 at 13:26

score 2 · Answer 1 · answered Aug 07 '14 at 13:26

2

that's because items isn't a List<T>, it's a Dictionary If you want to add to a Dictionary, you need to provide a key (first parameter) and a value (second parameter)

since your value type of the dictionary is List<String>, the second parameter must be a List<string>

Something along the lines of

items.Add(dataReader[0].ToString(), dataReader.ToList().convertAll(itm => itm.toString()));

answered Aug 07 '14 at 13:26

Timothy Groote

8,614
26
52

note that you can't really cast a `DataReader` to `List` like that. if you want to know how to do that, look here : http://stackoverflow.com/questions/1464883/how-can-i-easily-convert-datareader-to-listt – Timothy Groote Aug 07 '14 at 13:28
I tried this `string data = dataReader[0].ToString(); items.Add(data, data.ToList().convertAll(itm => itm.toString()));` and get an error around convertAll, `System.Collections.Generic.List does not contain a definition for 'convertAll' – user3723240 Aug 07 '14 at 13:36
Read the comment i posted above yours... in a perfect world, we'd be able to solve that issue so simply, but unfortunately, it's not a perfect world. – Timothy Groote Aug 07 '14 at 14:27

Bart van der Drift · Accepted Answer · 2014-08-07T14:00:44.967

2

Use a List and not a Dictionary:

 public class AirportClass
    {
        private string connectionString;
        private SqlConnection connection;
        private SqlCommand command;
        private List<string> items;

        public AirportClass()
        {
            connectionString = @"Server=server;database=database;uid=username;pwd=password;";
        }

        public List<string> getListItems()
        {
            items = new List<string>();
            connection = new SqlConnection(connectionString);
            command = new SqlCommand("SELECT * FROM Table");
            command.Connection = connection;
            connection.Open();
            SqlDataReader dataReader = command.ExecuteReader();
            while (dataReader.Read())
            {
                string data = dataReader.GetValue(0).ToString();
                items.Add(data);
            }
            connection.Close();
            return items;
        }
    }

edited Aug 07 '14 at 14:00

answered Aug 07 '14 at 13:27

Bart van der Drift

1,287
12
30

This works, but it only returns the first row [0] how would I get all rows? – user3723240 Aug 07 '14 at 13:37
Use dataReader.GetString(0) instead of dataReader[0].ToString() – Bart van der Drift Aug 07 '14 at 13:46
This gives me an error `Unable to cast object of type 'System.Int32' to type 'System.String' – user3723240 Aug 07 '14 at 13:52

score 1 · Answer 3 · answered Aug 07 '14 at 13:27

1

You need to supply a key and a value to a Dictionary.

answered Aug 07 '14 at 13:27

Alan B

4,086
24
33

C# ASP.NET - No overload for method 'Add' takes 1 arguments

3 Answers3