Adding fields depending on event message in Logstash not working

I have solved the problem. I get the expected results with the following code in "logstash.conf":

input {   file {    path => "C:\xxx.log"  }}filter {  grok {    patterns_dir => "C:\elk\patterns"    match => [ "message", "%{ERROR1:error1}" ]    match => [ "message", "%{ERROR2:error2}" ]  }  if [message] =~ /error1_regex/ {    grok {        patterns_dir => "C:\elk\patterns"        match => [ "message", "%{ERROR1:error1}" ]    }    mutate {        add_field => [ "id_error", "1" ]        add_field => [ "descripcio", "Error1!" ]        remove_field => [ "message" ]        remove_field => [ "error1" ]    }  }  else if [message] =~ /error2_regex/ {    grok {        patterns_dir => "C:\elk\patterns"        match => [ "message", "%{ERROR2:error2}" ]    }    mutate {        add_field => [ "id_error", "2" ]        add_field => [ "descripcio", "Error2!" ]        remove_field => [ "message" ]        remove_field => [ "error2" ]    }  }  if ("_grokparsefailure" in [tags]) { drop {} }}output {  elasticsearch {    host => "localhost"    protocol => "http"    index => "xxx-%{+YYYY.MM.dd}"  }}