How to display list items on console window in C#

Question

I have a List that contains all databases names. I have to display the items contained in that list in the Console (using Console.WriteLine()). How can I achieve this?

Answer 1

Actually you can do it pretty simple, since the list have a ForEach method and since you can pass in Console.WriteLine as a method group. The compiler will then use an implicit conversion to convert the method group to, in this case, an Action<int> and pick the most specific method from the group, in this case Console.WriteLine(int):

  var list = new List<int>(Enumerable.Range(0, 50));

  list.ForEach(Console.WriteLine);

Works with strings too =)

To be utterly pedantic (and I'm not suggesting a change to your answer - just commenting for the sake of interest) Console.WriteLine is a method group. The compiler then uses an implicit conversion from the method group to Action<int>, picking the most specific method (Console.WriteLine(int) in this case).

Answer 2

While the answers with List<T>.ForEach are very good.

I found String.Join<T>(string separator, IEnumerable<T> values) method more useful.

Example :

List<string> numbersStrLst = new List<string>
            { "One", "Two", "Three","Four","Five"};

Console.WriteLine(String.Join(", ", numbersStrLst));//Output:"One, Two, Three, Four, Five"

int[] numbersIntAry = new int[] {1, 2, 3, 4, 5};
Console.WriteLine(String.Join("; ", numbersIntAry));//Output:"1; 2; 3; 4; 5"

Remarks :

If separator is null, an empty string (String.Empty) is used instead. If any member of values is null, an empty string is used instead.

Join(String, IEnumerable<String>) is a convenience method that lets you concatenate each element in an IEnumerable(Of String) collection without first converting the elements to a string array. It is particularly useful with Language-Integrated Query (LINQ) query expressions.

This should work just fine for the problem, whereas for others, having array values. Use other overloads of this same method, String.Join Method (String, Object[])

Reference: https://msdn.microsoft.com/en-us/library/dd783876(v=vs.110).aspx

Answer 3

Assuming the items override ToString appropriately:

public void WriteToConsole(IEnumerable items)
{
    foreach (object o in items)
    {
        Console.WriteLine(o);
    }
}

(There'd be no advantage in using generics in this loop - we'd end up calling Console.WriteLine(object) anyway, so it would still box just as it does in the foreach part in this case.)

EDIT: The answers using List<T>.ForEach are very good.

My loop above is more flexible in the case where you have an arbitrary sequence (e.g. as the result of a LINQ expression), but if you definitely have a List<T> I'd say that List<T>.ForEach is a better option.

One advantage of List<T>.ForEach is that if you have a concrete list type, it will use the most appropriate overload. For example:

List<int> integers = new List<int> { 1, 2, 3 };
List<string> strings = new List<string> { "a", "b", "c" };

integers.ForEach(Console.WriteLine);
strings.ForEach(Console.WriteLine);

When writing out the integers, this will use Console.WriteLine(int), whereas when writing out the strings it will use Console.WriteLine(string). If no specific overload is available (or if you're just using a generic List<T> and the compiler doesn't know what T is) it will use Console.WriteLine(object).

Note the use of Console.WriteLine as a method group, by the way. This is more concise than using a lambda expression, and actually slightly more efficient (as the delegate will just be a call to Console.WriteLine, rather than a call to a method which in turn just calls Console.WriteLine).

Answer 4

You can also use List's inbuilt foreach, such as:

List<T>.ForEach(item => Console.Write(item));

This code also runs significantly faster!

The above code also makes you able to manipulate Console.WriteLine, such as doing:

List<T>.ForEach(item => Console.Write(item + ",")); //Put a,b etc.

Answer 5

Console.WriteLine(string.Join<TYPE>("\n", someObjectList));

Answer 6

I found this easier to understand:

List<string> names = new List<string> { "One", "Two", "Three", "Four", "Five" };
        for (int i = 0; i < names.Count; i++)
        {
            Console.WriteLine(names[i]);
        }

Answer 7

Assume that we need to view some data in command prompt which are coming from a database table. First we create a list. Team_Details is my property class.

    List<Team_Details> teamDetails = new List<Team_Details>();

Then you can connect to the database and do the data retrieving part and save it to the list as follows.

            string connetionString = "Data Source=.;Initial Catalog=your DB name;Integrated Security=True;MultipleActiveResultSets=True";
            using (SqlConnection conn = new SqlConnection(connetionString)){
            string getTeamDetailsQuery = "select * from Team";
            conn.Open();
            using (SqlCommand cmd = new SqlCommand(getTeamDetailsQuery, conn))
                    {
                        SqlDataReader rdr = cmd.ExecuteReader();
                    {
                        teamDetails.Add(new Team_Details
                        {
                            Team_Name = rdr.GetString(rdr.GetOrdinal("Team_Name")),
                            Team_Lead = rdr.GetString(rdr.GetOrdinal("Team_Lead")),
                        });
                    }

Then you can print this list in command prompt as follows.

foreach (Team_Details i in teamDetails)
                        {
                            Console.WriteLine(i.Team_Name);
                            Console.WriteLine(i.Team_Lead);
                        }