Accumulate [C #]-1, 1, 2, 3, 5, 8, 13, 21 .... Calculate 30th bits (recursion )!

Question: Uses Recursion to calculate 1, 1, 2, 3, 5, 8, 13, and 21 ...... 30th bits!

Effect:

Code:

 1   Protected   Void Button#click ( Object  Sender, eventargs E)  2   {  3               If (Tb1.text! = "" & Tb1.text! = Null  )  4  {  5                   If (! Isnum (tb1.text ))  6   {  7 Response. Write ( "  <SCRIPT type = 'text/JavaScript '> alert ('Enter the number'); </SCRIPT>  "  );  8   }  9                   Else 10   {  11                       Int A = Convert. toint32 (tb1.text );  12 Tb2.text = Convert. tostring (FOO ());  13   }  14   }  15               Else  16   { 17 Response. Write ( "  <SCRIPT type = 'text/JavaScript '> alert ('cannot be blank'); </SCRIPT>  "  );  18   }  19   }  20           Public   Static   Int Foo ( Int  I) 21   {  22               If (I < 0  )  23   {  24                   Return   0  ;  25   }  26               Else   If (I>0 & I <= 2  )  27   {  28                   Return   1  ;  29   }  30               Else  31   {  32                   Return Foo (I-1 ) + Foo (I- 2  );  33   }  34   }  35           Public   Static   Bool Isnum ( String  S)  36   {  37               String Pattern = @"  ^ \ D * $  "  ;  38               Return  RegEx. ismatch (S, pattern );  39 }