How can I insert an "array" of strings into a value?

Console.ReadLine() only reads one line. string input = Console.ReadLine() reads first line When you get into new line. In your case only first line is read then for the second line your program only gets first character and exits.

Check This:

    int numberOfElements = Convert.ToInt32(Console.ReadLine());   

    int sum= 0;
    for (int i=0; i< numberOfElements; i++)
    {

        string input = Console.ReadLine();     
        sum += Array.ConvertAll(input.Split(' '), int.Parse).Sum();
    }

    Console.WriteLine(sum);

Working Fiddle

Obviously when you paste in Carriage returns, ReadLine only takes up to the first Carriage Return, you will need a loop of some description

int numberOfElements = Convert.ToInt32(Console.ReadLine());

var sb = new StringBuilder();

for (int i = 0; i < numberOfElements; i++)
{
   Console.WriteLine($"Enter value {i+1}");
   sb.AppendLine(Console.ReadLine());
}

var input = sb.ToString();

// do what ever you want here

Console.ReadKey();

I'm assuming that you're looking for a way to allow a user to paste something from another source into your console program, so you're looking for an answer where you can process a multi-line string input from the user (where they paste a string that contains one or more newline characters).

If this is the case, then one way to do this would be to check the value of Console.KeyAvailable after the first call to ReadLine to see if there's still more input in the buffer, and if there is, add it to the input you've already captured.

For example, here's a method that takes in a prompt (to display to the user), and then returns a List<string> that contains an entry for each row the user pasted (or typed):

private static List<string> GetMultiLineStringFromUser(string prompt)
{
    Console.Write(prompt);

    // Create a list and add the first line to it
    List<string> results = new List<string> { Console.ReadLine() };

    // KeyAvailable will return 'true' if there is more input in the buffer
    // so we keep adding the lines until there are none left
    while(Console.KeyAvailable)
    {
        results.Add(Console.ReadLine());
    }

    // Return the list of lines
    return results;
}

In use, this might look something like:

private static void Main()
{
    var input = GetMultiLineStringFromUser("Paste a multi-line string and press enter: ");

    Console.WriteLine("\nYou entered: ");
    foreach(var line in input)
    {
        Console.WriteLine(line);
    }

    GetKeyFromUser("\nDone!\nPress any key to exit...");
}

Output

What you do next depends on what you want to accomplish. If you want to take all the lines, split them on the space character, and return all the results as a list of individual integers, you could do something like this:

private static void Main()
{
    int temp = 0;

    List<int> numbers =
        GetMultiLineStringFromUser("Paste a multi-line string and press enter: ")
            .SelectMany(i => i.Split()) // Get all the individual entries
            .Where(i => int.TryParse(i, out temp)) // Where the entry is an int
            .Select(i => Convert.ToInt32(i)) // And convert the entry to an int
            .ToList();

    Console.WriteLine("\nYou entered: ");
    foreach (var number in numbers)
    {
        Console.WriteLine(number);
    }

    GetKeyFromUser("\nDone!\nPress any key to exit...");
}

Output

Or you could even do something fancy like:

Console.WriteLine($"\n{string.Join(" + ", numbers)} = {numbers.Sum()}");

Output