Details of the method of C# function returning multiple values

introduction

According to the C# language specification, it is impossible to return multiple values ​​from a method. Using some other features provided by C#, we can return multiple values ​​to the caller method. This article outlines some available alternatives to achieve this.

1. Use the ref parameter

We can userefKeywords Return values ​​to the caller by reference. We can use it to return multiple values ​​from a method,

As shown below:

using System;
public class Example
{
    private static void fun(ref int x, ref int y)
    {
        x = 1;
        y = 2;
    }

    public static void Main()
    {
        int x = 0;
        int y = 0;
 
        fun(ref x, ref y);
 
        ("x = {0}, y = {1}", x, y);
    }
}
/*
     Output: x = 1, y = 2
 */

Please note thatrefKeywords do not apply toAsyncandIteratormethod.

2. Use out parameter modifier

outKeywords cause parameters to be passed by reference. It's like the ref keyword, except that ref requires that it be initialized before passing the variable.

The following example demonstrates using the out parameter to return multiple values ​​from a method.

using System;
 
public class Example
{
    private static void fun(out int x, out int y)
    {
        x = 1;
        y = 2;
    }
 
    public static void Main()
    {
        int x = 0;
        int y = 0;
 
        fun(out x, out y);
 
        ("x = {0}, y = {1}", x, y);
    }
}
 
/*
     Output: x = 1, y = 2
 */

Note that the out parameter does not apply to Async and Iterator methods.

3. Use tuple classes

A tuple is a data structure that allows you to easily package multiple values ​​into a single object. Tuples are usually used to return multiple values ​​from a method.

The following example creates a 2 tuple and from the fun() method:

using System;
 
public class Example
{
    private static Tuple<int, int> fun() {
        return (1, 2);
    }
 
    public static void Main()
    {
        Tuple<int, int> tuple = fun();
 
        ("x = {0}, y = {1}", tuple.Item1, tuple.Item2);
    }
}
 
/*
     Output: x = 1, y = 2
 */

tupleIt is a tuple that supports up to 7 elements, and any number of them need to be implemented in nesting and other methods.

The method of defining a function using tuples is as follows:

public static Tuple<string,string> TupleFun()
        {
            string[] T = {'hello','world'};
            Tuple<string, string> tup = new Tuple<string, string>(T[0], T[1]);
            return tup;
        }

Tuples also support multiple types of values.

public static Tuple<string,int> TupleFun()
        {
            string T = ‘hello';
            int q = 6;
            Tuple<string, int> tup = new Tuple<string, int>(T, q);
            return tup;
        }

When calling a function, use Item* to call elements within the tuple.

var tuple = TupleFun();
print(tuple.Item1);
print((tuple.Item2));

4. Use C#7 ValueTuple

Value tuples, introduced in .NET Framework 4.7, are tuple types that are used to provide runtime implementations of tuples in C#. Like a tuple class, we can use it to return multiple values ​​from a method in a more efficient way.

The following example uses type inference to deconstruct the 2 tuple returned by the method.

using System;
 
public class Example
{
    private static (int, int) fun() {
        return (1, 2);
    }
 
    public static void Main()
    {
        (int x, int y) = fun();
 
        ("x = {0}, y = {1}", x, y);
    }
}
 
/*
     Output: x = 1, y = 2
 */

5. Use structure or class

Here, the idea is to return an instance of a class that contains all the fields we want to return. The following code example returns multiple values ​​from a method using struct.

using System;
 
public class Example
{
    private struct Pair
    {
        public int x;
        public int y;
    }
 
    private static Pair fun() {
        return new Pair { x = 1, y = 2 };
    }
 
    public static void Main()
    {
        Pair pair = fun();
 
        ("x = {0}, y = {1}", , );
    }
}
 
/*
     Output: x = 1, y = 2
 */

This is all about returning multiple values ​​from a method in C#.

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