c# - app stops responding with no apparent reason -

my dice roller app contains 7 text boxes (three pairs of 'no. of dice' , 'dice type' , bonus one) , button. intended each pair of text boxes read separately, , if doesn't contains valid numbers ('fate' , '%' read numbers app reasons) ignores it.

the problem when not enter valid numbers in 1 of 'no. of dice' text box app stops responding, , returns loading page.

note i've tested each method separately already.

here code:

namespace diceroller { public sealed partial class mainpage : diceroller.common.layoutawarepage {     public mainpage()     {         this.initializecomponent();     }      random r = new random();      //regular, untouched basic page code here      private void btnroll1_click(object sender, routedeventargs e)     {         //the problem number boxes.         list<int>[] results = new list<int>[3];         if (!(readinput(textboxnumber1.text) == 0 || readinput(textboxtype1.text) == 0))         {             results[0] = roll(readinput(textboxtype1.text), readinput(textboxnumber1.text));         }         if (!(readinput(textboxnumber2.text) == 0 || readinput(textboxtype2.text) == 0))         {             results[1] = roll(readinput(textboxtype2.text), readinput(textboxnumber2.text));         }         if (!(readinput(textboxnumber3.text) == 0 || readinput(textboxtype3.text) == 0))         {             results[2] = roll(readinput(textboxtype3.text), readinput(textboxnumber3.text));         }         textblockoutput1.text = "results:" + string.join(", ",results[0]) + ", " + string.join(", ", results[1]) + ", " + string.join(", ", results[2]) + system.environment.newline + "total:" + ((results[0].sum() + results[1].sum() + results[2].sum() + readinput(textboxbonus.text)).tostring());     }      //methods      private int readinput(string input) //tested     {         int returnvalue = 0;         if (int.tryparse(input, out returnvalue)) ; //the 'out' make sure number has passed         else if (input == "%") returnvalue = 100;         else if (input.tolower() == "fate") returnvalue = 6;         else if (input == "") ;         else textblockoutput1.text = "error: text boxes should contain number,       strings '%', 'fate'(not case sensitive) or blank";         return returnvalue;     }      private int roll(int dicetype) //tested     {         return r.next(dicetype - 1) + 1;     }      private list<int> roll(int dicetype, int dicenumber)//tested     {         list<int> results = new list<int>();         (int = 1; <= dicenumber; i++) results.add(roll(dicetype));//if 1 of no. textboxes read '0', couln't operate         return results;     } } 

}

-thanks in advance helpers

edit: looked @ debugger advised in comments (thanks) , error 'value cannot null'. value? doesn't give clues. again.

you've made array of lists

list<int>[] results = new list<int>[3];

what wanted list<int>() results = new list<int>();

then add values results.add(roll());

you'll have more debugging make sure there 3 values final text set

edit 2 supports theory

edit..

just realised have 2 roll methods, should initialize sucn before setting them

for(int = 0; < 3; i++) { results[i] = new list<int>(); }