💠 ASP.NET (C#) example

using System;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

public class BbbCreateWithOverride
{
    static string Endpoint = "https://bbb.example.com/bigbluebutton/api";
    static string Secret   = "YOUR_SHARED_SECRET";

    static string Sha1(string s)
    {
        using var sha = SHA1.Create();
        var bytes = sha.ComputeHash(Encoding.UTF8.GetBytes(s));
        var sb = new StringBuilder();
        foreach (var b in bytes) sb.Append(b.ToString("x2"));
        return sb.ToString();
    }

    public static async Task RunAsync()
    {
        var qs = new StringBuilder();
        qs.Append("name=").Append(Uri.EscapeDataString("Demo with Overrides"));
        qs.Append("&meetingID=demo-123");
        qs.Append("&attendeePW=ap");
        qs.Append("&moderatorPW=mp");
        qs.Append("&allowOverrideClientSettingsOnCreateCall=true");

        var checksum = Sha1("create" + qs + Secret);
        var url = $"{Endpoint}/create?{qs}&checksum={checksum}";

        var overrideJson =
            "{\"public\":{\"app\":{\"appName\":\"Greenlight\",\"helpLink\":\"greenlight.example.com\"}," +
            "\"defaultSettings\":{\"application\":{\"autoJoin\":true,\"askForConfirmationOnLeave\":false}," +
            "\"user\":{\"userSettingsStorage\":\"sessionStorage\",\"application\":{\"overrideLocale\":\"en\"}}}}}";

        var xmlBody = $"<modules><module name=\"clientSettingsOverride\"><![CDATA[{overrideJson}]]></module></modules>";

        using var http = new HttpClient();
        var content = new StringContent(xmlBody, Encoding.UTF8, "application/xml");
        var resp = await http.PostAsync(url, content);
        var xml = await resp.Content.ReadAsStringAsync();
        Console.WriteLine(xml);
    }
}