Problem with List (of Integer)

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hello

I am new with generic types.I have made a function which returns list of integers.

VB

Private Function calculate(ByVal eid As String, ByVal fn As String, ByVal from As String) As List(Of Integer)

Dim Sol As New List(Of Integer)

        Sol.Add(CountNoOfInstallment)
        Sol.Add(NoOfInstallment)
        Sol.Add(InstallmentAmount)
        Sol.Add(FinalAmount)

  End Function

here all the 4 values i have calculated inside this function. I want to know is this the the right way to do it ??

now i am calling this function on pageload

Dim MyList As List(Of Integer) = calculate(Request.QueryString("eid").ToString(), Request.QueryString("fn").ToString(), Year)

 Dim CountNoOFInstallment As Int32 = MyList.Item(0)
                Dim NoOfInstallment As Int32 = MyList.Item(1)

when i used breakpoints MyList shows nothing in it also there is error saying object refrence not set to an instance of object. I know there are many things wrong with the code. please tell me what is wrong and how can it be corrected. I googled but wasn't able to understand then my friend suggested me this website to ask help for.

Posted 20-Jun-12 18:59pm

Aakash Sharma

Updated 20-Jun-12 19:05pm

v4

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Pankaj Nikam 21-Jun-12 1:22am

Have you verified that are getting the values inside the QueryStrings you mentioned?

Aakash Sharma 21-Jun-12 1:33am

yeah!! there are values inside query string.

Pankaj Nikam 21-Jun-12 4:24am

Check out the answer I have mentioned below. Does it help? If it does, please mark it as answer.

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Pankaj Nikam · Answer 1 · 2012-06-20T19:25:00

I guess the

VB

Return

statement is missing from the Function calculate.

Please include the following line before the

VB

End Function

VB

Return Sol

So the overall code will look like... :

VB

Private Function calculate(ByVal eid As String, ByVal fn As String, ByVal from As String) As List(Of Integer)
'Your calculations here

Dim Sol As New List(Of Integer)
Sol.Add(CountNoOfInstallment)
Sol.Add(NoOfInstallment)
Sol.Add(InstallmentAmount)
Sol.Add(FinalAmount)

Return Sol

End Function

Sergey Alexandrovich Kryukov · Answer 2 · 2012-06-20T19:25:00

Yes, many things are wrong, but major wrong thing is that nothing is clear. Next time, try to create a very short but complete code sample for the sole purpose of addressing a particular isolated problem and asking a question (but in many cases it will help you to find the solution by yourself).

Let's see:
The method calculate accepts two strings which are not used in its code. Why would you need those two parameters? Now, you don't show where CountNoOfInstallment, NoOfInstallment, InstallmentAmount, FinalAmount come from? Not from parameters. They must come from some external context; they could be the members of declaring class. Why showing this code if you don't show their declaration.

But the main problem is: you do not return anything (it should not compile). You see, you instantiate Sol (do yourself a big favor, never use abbreviations in variable names), add four elements and just return nothing. The result of this operation will be lost and eventually garbage-collected because you simply leave it unreachable (http://en.wikipedia.org/wiki/Garbage_collection_%28computer_science%29#Reachability_of_an_object[^]). Return the instance of the list you create. That's it.

—SA

Problem with List (of Integer)

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