C# methods with multiple return parameters [duplicate]

This question already has answers here: Return multiple values to a method caller (28 answers) Closed 9 years ago.

Is there a need for multiple return parameters in c#/.net?

public string, string GetFirstNameAndLastName(int id)
{
    var person = from p in Peop开发者_JS百科le
                 where p.Id = id
                 select p;
    return(p.FirstName, p.LastName);
}

Usage:

public void Main(string[] args)
{
    string firstName, lastName;
    (firstName, lastName) = GetFirstNameAndLastName(1);

    Console.WriteLine(firstName + ", " + lastName);
}

---

You can achieve this in a lightweight fashion using Tuple in C# 4.0

public Tuple<string, string> GetFirstNameAndLastName(int id)
{
   var person = from p in People
             where p.Id = id
             select p;
   return new Tuple<string, string>(p.FirstName, p.LastName);

   // OR
   // return Tuple.Create(p.FirstName, p.LastName);
}

System.Tuple also has the benefit of interoperating with F# native tuple type (well, it IS F#'s native tuple type, there just happens to be F#-specific syntax support for declaring tuples and functions that return them).

Given the existence of multiple approaches here: System.Tuple, multiple out parameters or returning a POCO with FirstName and LastName properties, I suspect that Anders Hejlsberg is probably not going to add explicit support for multiple return values.

---

No, just use out parameters.

public void GetFirstNameAndLastName(int id, out string first, out string last)
{
    var person = from p in People
                 where p.Id = id
                 select p;
    first = p.FirstName;
    last = p.LastName;
}

---

As suggested by @James Webster you can use tuple or you can use dynamic and ExpandoObject

class Program
{
    static void Main(string[] args)
    {
        var d = GetUserDynamic();
        Console.WriteLine("{0}.{1}", d.FirstName, d.LastName);
    }

    private static dynamic GetUserDynamic()
    {
        dynamic d = new ExpandoObject();
        d.FirstName = "amandeep";
        d.LastName = "tur";
        return d;
    }
}

---

No. You should return a more useful data type like a class if the elements are related.

public MyPersonClassGetFirstNameAndLastName(int id)
{
    var person = from p in People
                 where p.Id = id
                 select p;

    MyPersonClassreturnValue = new MyPersonClass;
    returnValue.FirstName = p.FirstName; 
    returnValue.LastName= p.LastName;
    return returnValue;
}

---

Next to the possibilities pointed out in other answers, there is are more ways to archieve this:

1. create your own return type (similar to the Tuple method) and return an instance of it
2. ref parameters: http://msdn.microsoft.com/en-us/library/14akc2c7%28v=vs.80%29.aspx

---

Depends on the situation. In your case you could return the whole person record back,

public string, string GetFirstNameAndLastName(int id)
{
    var person = from p in People
             where p.Id = id
             select p;
    return person;
}

or if the situation required it you could create your own data type.

---

You can do what you want like this:

public void GetFirstNameAndLastName(int id, out string firstName, out string lastName)
{
    var person = from p in People
                 where p.Id = id
                 select p;
    firstName = p.FirstName;
    lastName =  p.LastName;
}

and then call it like this:

public void Main(string[] args)
{
    string firstName, lastName;
    GetFirstNameAndLastName(1, out firstName, out lastName);

    Console.WriteLine(firstName + ", " + lastName);
}