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for(int i = 0;i<arr.Length && arr[i]!=valueToFind;i++) 
{
}

int i = 0;
while (i<arr.Length && arr[i]!=valueToFind)
i++;

Book[] arr = books; 
for(int i = 0; i<arr.Length; i++) 
{
  int books_index = i;
  Book book = arr[books_index];

  if(book.name == find_book) {
    return books_index;
  }
  else if(book.name != find_book) {
    continue;
  }
  else {
    found_flag = false;
  }
}

q1:
    if((pc.Current>='0'&& pc.Current<='9')||
        (pc.Current>='A'&& pc.Current<='Z')||
        (pc.Current=='_')||
        (pc.Current>='a'&& pc.Current<='z')) {
        sb.Append((char)pc.Current);
        pc.Advance();
        goto q1;
    }
    return new System.Collections.Generic.KeyValuePair<System.String,string>("id",sb.ToString());