UML is attached. I want to create a readonly property of pre which is an array of string. When I create an object in the main and try to set name and pre it is showing me an error.

UML

using System;

class Unit
{
    private string _name;
    private string[] _pre;

    public Unit(string name, string[] pre)
    {
        _name = name;
        _pre = new string[2];
    }

    public string Name { get { return _name; } }
    public string[] Pre { get { return _pre; } }
}

class Program
{
    public static void DisplayInfo(Unit[] _u)
    {
        for (int i = 0; i < 2; i  )
        {
            Console.WriteLine(_u[i].Name   _u[i].Pre);
        }
    }

    static void Main(string[] args)
    {
        Unit[] unitarraytest = new Unit[2];

        unitarraytest[0] = new Unit("test 1", "test 3");
        unitarraytest[1] = new Unit("test 2", "test 4");

        DisplayInfo(unitarraytest);
    }
}

CodePudding user response：

Your example makes little sense. You Unit constructor takes a parameter for "Pre", but immediately throws it away and allocates a new empty string array instead. It should probably be written like

class Unit
{
    public Unit(string name, string[] pre)
    {
        Name = name;
        Pre  = pre;
    }

    public string Name { get;}
    public string[] Pre { get;}
}

When creating Unit objects you actually need to create an array for the "Pre" parameter. Like new Unit("Name", new []{"pre1", "pre2"});

And when outputting the strings you need to access the individual strings in the array, or combine them to a larger string, for example like Console.WriteLine(_u[i].Name string.Join(" , ", _u[i].Pre));