Help creating alphanumeric string

Projects Programming
5

I just need help making the function to randomly generate an alphaNumerical string.
This is what I have so far but it's not working
void randStr(int lengt){
String randString;
int randN;
for(int x; x < lengt; x++){
randN = rand(97, 122);
randString = randString + to_string(randN);
randN = rand(0, 9);
randString = randString + to_string(randN);
}
}