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up vote 0 down vote favorite

i have this piece of code here , basically i am doing a for loop as i retrieve records from database( using entity framework ) but when i want to compare using if statement theres an error :

       IList<Model.question> lstQuestion = qn.GetRecords(taskID, activityID);

        for(int i = 0 ; i <lstQuestion.Count()-1 ; i++)
        {
             .... //code here

            if(lstQuestion[i].QuestionNo == lstQuestion[i++].QuestionNo) // error at i++
            {
                tb.Text = lstQuestion[i++].QuestionContent;
                sp1.Children.Add(tb);
            }

i tried

lstQuestion.Count() instead of lstQuestion.Count()-1;

also doesn't work .

QuestionNo is a column in my database table .

Full ERROR :

enter image description here

When i remove the whole if statement , it works fine .

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InnerException says {"Specified Visual is already a child of another Visual or the root of a CompositionTarget."} –  user2376998 Jul 17 '13 at 3:37
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5 Answers

up vote 0 down vote

you're incrementing i three times. Try this:

for(int i = 0 ; i <lstQuestion.Count(); i++)
        {
             .... //code here

            if(lstQuestion[i].QuestionNo == 1stQuestion[i+1].QuestionNo) // error at i++
            {
                tb.Text = lstQuestion[i+1].QuestionContent;
                sp1.Children.Add(tb);
            }
share|improve this answer
    
tried , i have updated the error –  user2376998 Jul 17 '13 at 3:41
    
it sounds like it's the line sp1.Children.Add(tb); that's causing you trouble. I'm not entirely sure what you're trying to do there without seeing it in context. tb is apparently already a child of something else. –  Bodacious Jul 17 '13 at 4:00
    
i didn't paste the full code because i tot it was not related , sp1 is the name of the stackpanel that i am adding the tb to. –  user2376998 Jul 17 '13 at 4:00
    
i removed sp1.children.add(tb) and tb.text line but i keep the if statement , the error is still –  user2376998 Jul 17 '13 at 4:01
    
Is it the exact same error? –  Bodacious Jul 17 '13 at 4:06
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up vote 0 down vote

you have a number 1 in the == 1stQuestion[i] instead of the lowercase L like in the ohter lstQuestion[i] references.

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typo , i changed it already –  user2376998 Jul 17 '13 at 3:38
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up vote 0 down vote

the above answers regarding (i++) are correct. also, since collections use zero based index, your should use (Count() - 2) --- // (Count() -2) + 1 is your last item in the collection

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up vote 0 down vote

This should solve your problem with if statement.

    for(int i = 0 ; i <lstQuestion.Count()-1; i++)
    {
         .... //code here

        if(lstQuestion[i].QuestionNo == 1stQuestion[i+1].QuestionNo) 
        {
            tb.Text = lstQuestion[i+1].QuestionContent;
            sp1.Children.Add(tb);
        }

But i think you are getting error on this line 

                      sp1.Children.Add(tb);
share|improve this answer
add comment
up vote 0 down vote

Try using ++i instead of i++. 

IList<Model.question> lstQuestion = qn.GetRecords(taskID, activityID);

        for(int i = 0 ; i <lstQuestion.Count()-1 ; i++)
        {
             .... //code here

            if(lstQuestion[i].QuestionNo == lstQuestion[++i].QuestionNo) // error at i++
            {
                tb.Text = lstQuestion[i].QuestionContent;
                sp1.Children.Add(tb);
            }
share|improve this answer
add comment

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