using System;
using System.Text.RegularExpressions;
public class Test
{
public static void Main()
{
string pattern = @"(?i)\bInvoice[ _:.]+(?<anr>[A-Z/-]*[0-9][A-Z0-9/-]*)(?!\S)";
string input = @"Payer:_xxxxxxx
Waybill Invoice_5IN280625-3/4 Nimetus_EAN
Invoice issuer: John
Selle Invoice tasumisel palume m lisada Kesolev Invoice on poolte
vahel Invoice mittetähtaegsel tasumisel on müüjal õigus nõuda viivist 0,1% tasumata summalt päevas.
Kuni Invoice Second280625-3/4 sumiseni k";
Match m = Regex.Match(input, pattern);
if (m.Success) {
Console.WriteLine(m.Groups["anr"]);
}
}
}
dXNpbmcgU3lzdGVtOwp1c2luZyBTeXN0ZW0uVGV4dC5SZWd1bGFyRXhwcmVzc2lvbnM7CgpwdWJsaWMgY2xhc3MgVGVzdAp7CglwdWJsaWMgc3RhdGljIHZvaWQgTWFpbigpCgl7CiAgICAgICAgc3RyaW5nIHBhdHRlcm4gPSBAIig/aSlcYkludm9pY2VbIF86Ll0rKD88YW5yPltBLVovLV0qWzAtOV1bQS1aMC05Ly1dKikoPyFcUykiOwogICAgICAgIHN0cmluZyBpbnB1dCA9IEAiUGF5ZXI6X3h4eHh4eHgKV2F5YmlsbCBJbnZvaWNlXzVJTjI4MDYyNS0zLzQgTmltZXR1c19FQU4gIApJbnZvaWNlIGlzc3VlcjogSm9obgpTZWxsZSBJbnZvaWNlIHRhc3VtaXNlbCBwYWx1bWUgbSBsaXNhZGEgS2Vzb2xldiBJbnZvaWNlIG9uIHBvb2x0ZQp2YWhlbCBJbnZvaWNlIG1pdHRldMOkaHRhZWdzZWwgdGFzdW1pc2VsIG9uIG3DvMO8amFsIMO1aWd1cyBuw7V1ZGEgdmlpdmlzdCAwLDElIHRhc3VtYXRhIHN1bW1hbHQgcMOkZXZhcy4KS3VuaSBJbnZvaWNlICBTZWNvbmQyODA2MjUtMy80IHN1bWlzZW5pIGsiOwogICAgCiAgICAgICAgTWF0Y2ggbSA9IFJlZ2V4Lk1hdGNoKGlucHV0LCBwYXR0ZXJuKTsKICAgICAgICBpZiAobS5TdWNjZXNzKSB7CiAgICAgICAgICAgIENvbnNvbGUuV3JpdGVMaW5lKG0uR3JvdXBzWyJhbnIiXSk7CiAgICAgICAgfQoJfQp9Cg==