using System;

using System.Text;

public class Program

{

    public static readonly string _identityClientUrlDev = "https://localhost:44392";

    public static readonly string _identityPostingListApi = "/api/app/posting/posting-list";

    public static void Main()

    {

        var requestUrl = $"{_identityClientUrlDev}{_identityPostingListApi}?idList=16144&idList=16669&idList=16788";

        var idList = new int[] { 16144, 16669, 16788 };

        var generatedUrl = BuildUrl(idList);

        var buildUrl = Builder(idList);

        // Console.WriteLine(generatedUrl);

        Console.WriteLine(String.Equals(requestUrl, generatedUrl));

        Console.WriteLine(buildUrl);

        Console.WriteLine(String.Equals(requestUrl, buildUrl));

    }

    public static string BuildUrl(int[] idList) 

    {

        var identityApiUrl = $"{_identityClientUrlDev}{_identityPostingListApi}";

        var sb = new StringBuilder();

        sb.Append(identityApiUrl);

        sb.Append("?");

        for (int i = 0; i < idList.Length; i++)

        {

            sb.Append("idList=");

            sb.Append(idList[i]);

            if(i < idList.Length - 1)

                sb.Append("&");

        }

        return sb.ToString();

    }

    public static string Builder(int[] idList)

    {

        var identityApiUrl = $"{_identityClientUrlDev}{_identityPostingListApi}";

        var idListParameters = string.Join("&", Array.ConvertAll(idList, id => $"idList={id}"));

​

        var sb = new StringBuilder();

        sb.Append(identityApiUrl);

        sb.Append("?");

        sb.Append(idListParameters);

        return sb.ToString();

    }

}