CODEWITHSUNDEEP
c#tuples
junkone
junkone

Reputation: 1465

Cannot add tuple to list

I have a list of tuples and cannot add them to a list. What causes this compile error? https://dotnetfiddle.net/vhR3vP

    using System;
    using System.Collections.Generic;               
public class Program
{
    public static void Main()
    {
        Console.WriteLine("Hello World");
         List<Tuple<string,string,string,string,string,string,string,string>> ExecutionsDetailsTuple =new  List<Tuple<string,string,string,string,string,string,string,string>>(); // format executionid, symbol, quantity, price, tradedirection, orderaction, account, executiontime
        var person= Tuple.Create<string,string,string,string,string,string,string,string>("1","2","3","4","5","6","7","8");
        ExecutionsDetailsTuple.Add(person);
        
    }
}

compile error:

Compilation error (line 10, col 3): The best overloaded method match for 'System.Collections.Generic.List<System.Tuple<string,string,string,string,string,string,string,string>>.Add(System.Tuple<string,string,string,string,string,string,string,string>)' has some invalid arguments
Compilation error (line 10, col 30): Argument 1: cannot convert from 'System.Tuple<string,string,string,string,string,string,string,System.Tuple<string>>' to 'System.Tuple<string,string,string,string,string,string,string,string>'

Upvotes: 1

Views: 530

Answers (2)

Progman
Progman

Reputation: 19545

The return type of Tuple.Create<> with eight arguments is defined as:

Tuple<T1,T2,T3,T4,T5,T6,T7,Tuple<T8>>

Notice the Tuple<T8> at the end. You think you would create a Tuple<T1,T2,T3,T4,T5,T6,T7,T8> instance with the Tuple.Create() method, but you are not.

As the number of generic parameters for the Tuple class is limited to eight, but there might be a requirement for more than eight values, the class is designed that way, that the 8th generic parameter must be a Tuple type. So the general structure will be: seven values plus an additional Tuple for the remaining values. Assuming you want to create a tuple of 25 values, you would build a chain of four Tuple instances (7+7+7+4).

When you want to use a tuple of eight values you have to change the type of your variable to List<Tuple<string,string,string,string,string,string,string,Tuple<string>>>.

Upvotes: 2

Tomasz Juszczak
Tomasz Juszczak

Reputation: 2340

Tuples should not be used in "production code" unless you deal with CLI or some other you get your input from some other language.

Because of Generics limitations in C# Tuples can have at most 8 generic values. And as per documentation: The last element of an eight element Tuple must be a Tuple.

To remove this error, convert this tuple to class, or convert your tuple so it uses a Tuple as a last element

Upvotes: 1

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