"Error: invalid types 'char[int]' for array subscript" while trying to access an array with the keypad input

Using Arduino Programming Questions
#1 
#include <Keypad.h>
#include <IRremote.h>
const int ROW_NUM = 4; //four rows
const int COLUMN_NUM = 4; //four columns
int RECV_PIN = 11;
IRrecv irrecv(RECV_PIN);
decode_results results;
IRsend irsend;
int A[] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
int B[] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
int C[] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
int D[] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};

char keys[ROW_NUM][COLUMN_NUM] = {
  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte pin_rows[ROW_NUM] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
byte pin_column[COLUMN_NUM] = {6, 7, 8, 9}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

void setup(){
  Serial.begin(9600);
  Serial.begin(9600);
  irrecv.enableIRIn(); // Start the receiver
}

void loop(){
  char key = keypad.getKey();

  if (key == "#"){
    irsend.sendRC5(0x0, 8); //send 0x0 code (8 bits)
    delay(200);
    irsend.sendRC5(0x1, 8); 
    delay(200); 
    **char array_choice = keypad.getKey();** // The source of my misery
    if (array_choice == A) {
      int index_of_signal = keypad.getKey();
      if (index_of_signal == 0) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 1) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 2) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 3) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 4) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 5) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 6) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 7) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 8) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 9) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      }
    if (array_choice == B) {
      int index_of_signal = keypad.getKey();
      if (index_of_signal == 0) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 1) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 2) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 3) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 4) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 5) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 6) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 7) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 8) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      if (index_of_signal == 9) {
        irsend.sendRC5(array_choice[index_of_signal], 8);
        }
      }
    }
    if (key == "*") {
      if (irrecv.decode(&results)) {
      Serial.println(results.value, HEX);
      irrecv.resume();
      }
  }
}

This code is for a universal IR remote, it's supposed to get the value of the IR signal in the selected array and transmit the signal.

Yet when I try to get the keypad input to select the array the user would like to use, I get the error mentioned in the title. I know that my mistake is that the keypad is storing the selection as a char, because of that, it is unable to recognise that the input is supposed to select a specific array and access it.

How would I go about fixing this problem? Any help would be appreciated.

#2 

 if (key == "#"){

key is of type char but "#" is not. You should use '#' (single quotes NOT double quotes).

It's not clear whether the asterisks are really in the line that you marked. They don't belong, or perhaps you intended to confuse me.

#3

That’s because the call is non blocking so it probably return NO KEY (which is 0) and code goes on

And use single quotes for all your tests
if (array_choice == 'A') {

#4

If you want to wait for a key, use keypad.waitForKey() instead of keypad.getKey().