Error cs1503 argument 1 cannot convert from string to char

The problem is that I keep getting this error

Cannot convert from OmzetApplicatie.lib.Category to string

The error occurs on this line of code:

categories.Add(new Category(item));

Complete code:

List<string> categories;

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    string[] categorynames = { "Vlees", "Snacks", "Drank", "Groenten en Fruit", "Droge voeding", "Sauzen", "Diepvries" };

    foreach (string item in categorynames)
    {
        categories.Add(new Category(item));
    }

    Product[][] products = {
            new Product[] { new Product("gehakt", 6.4M, 5.30M), new Product("hamburger", 9.0M, 6.25M), new Product("kip", 9.7M, 7.13M), new Product("biefstuk", 17.9M, 13.38M), new Product("preparé", 10.3M, 7.86M) },
            new Product[] { new Product("chips", 1.8M, 1.51M), new Product("nootjes", 7.00M, 5.83M), new Product("suikerwafels", 0.9M, 0.73M), new Product("snoep", 1.9M, 1.34M) },
            new Product[] { new Product("water", 0.3M, 0.23M), new Product("cola", 2.0M, 1.55M), new Product("ice-tea", 1.8M, 1.23M), new Product("fanta", 1.8M, 1.34M), new Product("sprite", 1.8M, 1.36M) },
            new Product[] { new Product("appels", 1.2M, 1.03M), new Product("komkommer", 0.4M, 0.36M), new Product("paprika", 2.4M, 2.05M), new Product("banaan", 1.4M, 1.15M), new Product("champignons", 0.8M, 0.63M) },
            new Product[] { new Product("spaghetti", 1.3M, 1.05M), new Product("rijst", 2.2M, 2.03M), new Product("hamburgerbroodjes", 2.4M, 2.17M), new Product("brood", 1.4M, 1.03M), new Product("macaroni", 0.3M, 0.26M) },
            new Product[] { new Product("ketchup", 2.7M, 2.27M), new Product("mayonaise", 1.7M, 1.12M), new Product("pesto", 0.8M, 0.63M), new Product("tomatensaus", 0.5M, 0.38M) },
            new Product[] { new Product("ijs", 1.7M, 1.34M), new Product("frieten", 1.7M, 1.62M), new Product("kroketten", 3.2M, 3.05M), new Product("frikandel", 1.9M, 1.62M), new Product("pizza", 2.3M, 2.16M) }
    };

    for (int i = 0; i < products.Length; i++)
    {
        foreach (Product p in products[i])
        {
            categories[i].AddProduct(p);
        }
    }
}

This is my class from my class library

namespace OmzetApplicatie.lib
{
    public class Category
    {
        public string item;
        public string[] categorynames;

        public Category(string item)
        {
            this.item = item;
        }
    }
}

using System;
using System.IO;
using System.Collections.Generic;
 
namespace Grapher
{ class Program
{
    static void Main(string[] args)
    {
        string[] data = File.ReadAllLines("массив.txt");
        int length = data[0].Split(';').Length, i;
        Graph graph = new Graph();
        for (i = 0; i < length; i++)
        {
            string[] str = data[i].Split(';');
            var vertices = new Dictionary<char, int>();
            for (int j = 0; j < length; j++)
                if (Convert.ToInt32(str[j]) != 0)
                    vertices.Add(Char.Parse((j + 1).ToString()), Convert.ToInt32(str[j]));
 
            graph.add_vertex(Char.Parse((i + 1).ToString()), vertices);
        }
       
        string start = Console.ReadLine(); // Номер начального пункта
            string end = Console.ReadLine(); // Номер конечного пункта
        var result = graph.all_ways(start, end, "", 0);
 
        using (var sw = new StreamWriter("результат.txt"))
        {
            foreach (var item in result)
                sw.WriteLine(item);
            sw.WriteLine("Кратчайшее расстояние равно " + graph.shortest_path(start, end));
        }
        Console.Write("Результат был сохранен в файле результат.txt");
        Console.ReadLine();
    }
}
}

    class Graph
    {
        Dictionary<char, Dictionary<char, int>> vertices = new Dictionary<char, Dictionary<char, int>>();
        public void add_vertex(char name, Dictionary<char, int> edges)
        {
            vertices[name] = edges;
        }
        public List<string> all_ways(char current, char end, string path, int weight)
        {
            List<string> pathes = new List<string>();
            if (path.IndexOf(current.ToString() + " ") != -1)
 
                return pathes;
            else
                if (path == "")
                path = current.ToString() + " = 0";
            else
            {
                int index = path.IndexOf("=");
                string temp = path.Substring(0, index);
                string sum = path.Substring(index + 1);
                weight += Convert.ToInt32(sum);
                path = temp + "-> " + current.ToString() + " = " + weight.ToString();
            }
            if (current == end)
            {
                pathes.Add(path);
                return pathes;
            }
            foreach (KeyValuePair<char, int> pair in vertices[current])
            {
                List<string> result = all_ways(pair.Key, end, path, pair.Value);
                if (result.Count != 0)
                    pathes.AddRange(result);
            }
            return pathes;
        }
        public int shortest_path(char start, char finish)
        {
            var previous = new Dictionary<char, char>();
            var distances = new Dictionary<char, int>();
            var nodes = new List<char>();
 
            List<char> path = null;
 
            foreach (var vertex in vertices)
            {
                if (vertex.Key == start)
                {
                    distances[vertex.Key] = 0;
                }
                else
                {
                    distances[vertex.Key] = int.MaxValue;
                }
 
                nodes.Add(vertex.Key);
            }
 
            while (nodes.Count != 0)
            {
                nodes.Sort((x, y) => distances[x] - distances[y]);
 
                var smallest = nodes[0];
                nodes.Remove(smallest);
 
                if (smallest == finish)
                {
                    path = new List<char>();
                    while (previous.ContainsKey(smallest))
                    {
                        path.Add(smallest);
                        smallest = previous[smallest];
                    }
 
                    break;
                }
 
                if (distances[smallest] == int.MaxValue)
                {
                    break;
                }
 
                foreach (var neighbor in vertices[smallest])
                {
                    var alt = distances[smallest] + neighbor.Value;
                    if (alt < distances[neighbor.Key])
                    {
                        distances[neighbor.Key] = alt;
                        previous[neighbor.Key] = smallest;
                    }
                }
            }
            if (path.Count > 0)
                return distances[path[0]];
            else
                return 0;
        }
    }

Error cs1503 argument 1 cannot convert from string to char

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Answered by:

Question

HI ! I am expirienced C++ programmer , but new to C#

1. What is the difference between string and String ? when is each one used ?

2. I tried to use «ToCharArray» , because I need the text in simple characters array.

private System.Windows.Forms.TextBox UserName ;

char [] name1;

name1 = new char [64];

name1 = this.UserName.Text.ToCharArray();

But when tried to print it :

MessageBox.Show( name1.ToString ());

it printed on the meesage box : «System.char [] » , which is not the text that is there.

MessageBox.Show( this.UserName.Text ); worked fine

3. I dont know what is wrong . ?

4. Is c# characters array is like C character array or not ?

good morning sunshine

Answers

I’m not sure why you’re getting the compile error but you shouldn’t be. Maybe the following code (tested) will help.

For the dll file:

For the .Net app:

1) EntryPoint doesn’t need to be specified if your C# function declaration has the exact same name that’s exported from the dll.

2) When using pinvoke, you MUST be aware of and match the calling convention used by the C dll. In the above, I specified __stdcall in the dll because .Net defaults to WinApi (which means it uses __stdcall on Windows machines. cdecl on WindowsCE). If the calling convention is other than StdCall, you must specify it in your DllImport:

The bottom line is: If you don’t match the calling conventions you risk corrupting the stack (and getting program exceptions).

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