Csharp/C Sharp/Language Basics/Function Parameters

Arrays as Function Returns and Parameters

 
using System;
public class Starter {
    public static void Main() {
        int[] zArray = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
        string[] xArray = { "a", "b", "c", "d" };
        Console.WriteLine("List Numbers");
        MyClass.ListArray(zArray);
        Console.WriteLine("List Letters");
        MyClass.ListArray(xArray);
        Console.WriteLine("Total Numbers");
        MyClass.Total(zArray);
    }
}

public class MyClass {
    public static void ListArray(Array a) {
        foreach (object element in a) {
            Console.WriteLine(element);
        }
    }
    public static void Total(int[] iArray) {
        int total = 0;
        foreach (int number in iArray) {
            total += number;
        }
        Console.WriteLine(total);
    }
}

creates instances of a value and a reference type

 
using System;
class Starter {
    static void Main() {
        int localvalue = 5;
        MyClass objZ = new MyClass();
        DisplayType(localvalue);
        DisplayType(objZ);
    }
    static void DisplayType(object parameterObject) {
        Type parameterType = parameterObject.GetType();
        string name = parameterType.Name;
        Console.WriteLine("Type is " + name);
        if (name == "MyClass") {
            ((MyClass)parameterObject).Display();
        }
    }
}
class MyClass {
    public void Display() {
        Console.WriteLine("MyClass::Display");
    }
}

Passing parameters to methods

 
using System;
class ParameterTest {
    static void SomeFunction(int[] ints, int i) {
        ints[0] = 100;
        i = 100;
    }
    public static void Main() {
        int i = 0;
        int[] ints = { 0, 1, 2, 4, 8 };
        Console.WriteLine("i = " + i);
        Console.WriteLine("ints[0] = " + ints[0]);
        Console.WriteLine("Calling SomeFunction...");
        SomeFunction(ints, i);
        Console.WriteLine("i = " + i);
    }
}

Pass integer by reference

 
using System;
public class Starter {
    public static void MethodA(ref int parameter) {
        parameter = parameter + 5;
    }
    public static void Main() {
        int var = 2;
        MethodA(ref var);
        Console.WriteLine(var); // 7
    }
}

Pass valuel by pointer

 
using System;
public class Starter {
    public unsafe static void Main() {
        int val = 5;
        int* pA = &val;
        int* pB;
        pB = MethodA(pA);
        Console.WriteLine("*pA = {0} | *pB = {0}", *pA, *pB);
    }
    public unsafe static int* MethodA(int* pArg) {
        *pArg += 15;
        return pArg;
    }
}

ref pointer parameter

 
using System;
public class Starter {
    public unsafe static void Main() {
        int val = 5;
        int* pA = &val;
        Console.WriteLine("Original: {0}", (int)pA);
        MethodA(pA);
        Console.WriteLine("MethodA:  {0}", (int)pA);
        MethodB(ref pA);
        Console.WriteLine("MethodB:  {0}", (int)pA);
    }
    public unsafe static void MethodA(int* pArg) {
        ++pArg;
    }
    public unsafe static void MethodB(ref int* pArg) {
        ++pArg;
    }
}

Use out to mark an object parameter

 
using System;
class XInt {
    public int iField = 5;
}
class Starter {
    public static void MethodA(out XInt alias) {
        XInt inner = new XInt();
        alias = inner;
    }
    public static void Main() {
        XInt obj;
        MethodA(out obj);
        Console.WriteLine(obj.iField); // 5
    }
}

Use ref to mark an object parameter

 
using System;
public class XInt {
    public int iField = 2;
}
public class Starter {
    public static void MethodA(ref XInt alias) {
        XInt inner = new XInt();
        inner.iField = 5;
        alias = inner;
    }
    public static void Main() {
        XInt obj = new XInt();
        MethodA(ref obj);
        Console.WriteLine(obj.iField); // 5
    }
}