c# - Set datagrid row background color WPF - Loop -

i have 1 task go throw datagridrow , task. when finish set background color row. added cancel button stop task, , continue button continue finished last time. work perfect except changing background color row.

this xaml code, i'm new wpf it's not big datagrid

<datagrid       name="datagridviewmygroups"       grid.row="0" columnwidth="*"       verticalscrollbarvisibility="auto"       isreadonly="true"       selectionunit="fullrow"       selectionmode="single"          mousedoubleclick="datagridviewmygroups_mousedoubleclick"> </datagrid> 

here c# code changing background color.

datagridrow rowcolor = (datagridrow)datagridviewmygroups.itemcontainergenerator                     .containerfromindex(number);                                   rowcolor.background = new solidcolorbrush(system.windows.media.color.fromrgb(223, 227, 238));  

this code work when click on start button , change background color each row. problem when click cancel button , click on continue button, got nullreferenceexception. continue button check last id in database table.

int number=0; foreach (groupsinlist group in datagridviewmygroups.items) {    if (fbgroupid != null && check==true)    {        number++;        if (fbgroupid != grouplink)        {          continue;        }        check = false;        continue;    }       //do , change background (code above).      number++; } 

code continue button work except changing row's background.

update: code cancel button:

 if (messagebox.show("do want stop posting?", "confirmation",   messageboxbutton.yesno, messageboximage.question) == messageboxresult.yes)         {             tokensource.cancel();          } 

code continue button:

        int postid;         string fbgroupid;         int listid;          using (oledbconnection connection = new oledbconnection(conn))         {             //code getting value `db table`              postid = list[0].postid;             fbgroupid = list[0].fbgroupid;             listid = list[0].listforgroupid;         }          cmbselectlist.selectedvalue = listid;         cmbsavedposts.selectedvalue = postid;         loadgroupsinlist(); //maybe problem because here update(reload) datagrid again.          tokensource = new cancellationtokensource();          try         {                                           await taskposttogroup(tokensource.token, fbgroupid, true);         }         catch (operationcanceledexception ex)         {             system.windows.messagebox.show(ex.message, "canceled", messageboxbutton.ok, messageboximage.stop);         }         catch (nullreferenceexception)         {             //i don't have solution changing background color each row when continue button clicked         }         catch (exception ex)         {             system.windows.messagebox.show(ex.message + "\n\n" + ex.stacktrace, "exception", messageboxbutton.ok, messageboximage.error);         } 

ok think see problem now. it's there in own code:

int number=0; foreach (groupsinlist group in datagridviewmygroups.items) {     if (fbgroupid != null && check==true)     {         number++;         if (fbgroupid != grouplink)         {              continue;         }         check = false;         continue;     }     //do , change background (code above).    number++; } 

your foreach loop runs many times there rows in datagrid. inside increment number variable twice in cases depending on logic. is, if go in if statement increase once, , again @ end of loop. whenever go in if statement increment row count twice.

which why counter goes higher value actual number of rows have. need remove increment inside if statement.