Quick way to create a list of values in C#?

Check out C# 3.0's Collection Initializers.

var list = new List<string> { "test1", "test2", "test3" };

If you're looking to reduce clutter, consider

var lst = new List<string> { "foo", "bar" };

This uses two features of C# 3.0: type inference (the var keyword) and the collection initializer for lists.

Alternatively, if you can make do with an array, this is even shorter (by a small amount):

var arr = new [] { "foo", "bar" };

In C# 3, you can do:

IList<string> l = new List<string> { "test1", "test2", "test3" };

This uses the new collection initializer syntax in C# 3.

In C# 2, I would just use your second option.

IList<string> list = new List<string> {"test1", "test2", "test3"}

You can do that with

var list = new List<string>{ "foo", "bar" };

Here are some other common instantiations of other common Data Structures:

Dictionary

var dictionary = new Dictionary<string, string> 
{
    { "texas",   "TX" },
    { "utah",    "UT" },
    { "florida", "FL" }
};

Array list

var array = new string[] { "foo", "bar" };

Queue

var queque = new Queue<int>(new[] { 1, 2, 3 });

Stack

var queque = new Stack<int>(new[] { 1, 2, 3 });

As you can see for the majority of cases it is merely adding the values in curly braces, or instantiating a new array followed by curly braces and values.

You can drop the new string[] part:

List<string> values = new List<string> { "one", "two", "three" };

You can simplify that line of code slightly in C# by using a collection initialiser.

var lst = new List<string> {"test1","test2","test3"};

You can just:

var list = new List<string> { "red", "green", "blue" };

or

List<string> list = new List<string> { "red", "green", "blue" };

Checkout: Object and Collection Initializers (C# Programming Guide)

If you want to create a typed list with values, here's the syntax.

Assuming a class of Student like

public class Student {
   public int StudentID { get; set; }
   public string StudentName { get; set; }
 }   

You can make a list like this:

IList<Student> studentList = new List<Student>() { 
                new Student(){ StudentID=1, StudentName="Bill"},
                new Student(){ StudentID=2, StudentName="Steve"},
                new Student(){ StudentID=3, StudentName="Ram"},
                new Student(){ StudentID=1, StudentName="Moin"}
            };

If we assume there is a class named Country , than we can do like this:

var countries = new List<Country>
{
    new Country { Id=1, Name="Germany", Code="De" },
    new Country { Id=2, Name="France",  Code="Fr" }
};