/*
Ajouter votre référence web puis ajouter cette fonction dans la référence

protected override System.Net.WebRequest GetWebRequest(Uri uri)
{
    HttpWebRequest request;
    request = (HttpWebRequest)base.GetWebRequest(uri);

    if (PreAuthenticate)
    {
        NetworkCredential networkCredentials = Credentials.GetCredential(uri, "Basic");

        if (networkCredentials != null)
        {
            byte[] credentialBuffer = new UTF8Encoding().GetBytes(networkCredentials.UserName + ':' + networkCredentials.Password);
            request.Headers["Authorization"] = "Basic " + Convert.ToBase64String(credentialBuffer);
        }
        else
        {
            throw new ApplicationException("No network credentials");
        }
    }
    return request;
}
*/

string login = "";
string password = "";

// Create a new instance of the MD5CryptoServiceProvider object.
MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();

// Convert the input string to a byte array and compute the hash.	
byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(login + "|" + password));
StringBuilder sBuilder = new StringBuilder();
for (int i = 0; i < data.Length; i++)
{
    sBuilder.Append(data[i].ToString("x2"));
}
string hash = sBuilder.ToString();

        
EntrepriseService service = new EntrepriseService();
                        
NetworkCredential Auth = new NetworkCredential(login, hash);

Uri uri = new Uri(service.Url);
ICredentials credentials = Auth.GetCredential(uri, "Basic");
service.Credentials = credentials;

service.PreAuthenticate = true;