IndexOutOfRange Exception in code converted from VB to C#

Question

I have this VB code

 Public Function InitJobTicketConcaveItemsType() As JobTicketConcaveItemsType
        Dim OutData As JobTicketConcaveItemsType
        With OutData
            .NumJobItems = 1
            ReDim .JobItems(.NumJobItems - 1)
            .JobItems(0) = JobDataConcaveEnum.JDBDryData
        End With
        Return OutData
    End Function

The converted C# code

public static JobTicketConcaveItemsType InitJobTicketConcaveItemsType()
        {
            JobTicketConcaveItemsType OutData = default(JobTicketConcaveItemsType);
            var _with25 = OutData;

            _with25.NumJobItems = 1;
            // ERROR: Not supported in C#: ReDimStatement - replaced with the statement below
            Array.Resize(ref _with25.JobItems, _with25.NumJobItems - 1);

            _with25.JobItems[0] = FrontEndEnums.JobDataConcaveEnum.JDBDryData;
            return OutData;
        }

When I try to run the application , I get a the Error IndexOutOfRangeException was unhandled. I have made sure to use Array.Resize() to reallocate the array

The code in VB doesn´t give errors. Any clues ?

JDBDryData has been defined as below

public enum JobDataConcaveEnum
        {
            JDBWetData = 0,
            JDBDryData,
            JDBWetCylinder,
            JDBAxis
        }

I get the error at the statement

_with25.JobItems[0]=FrontEndEnums.JobDataConcaveEnum.JDBDryData;

Possible duplicate of [Redim Preserve in C#?](http://stackoverflow.com/questions/327916/redim-preserve-in-c) — Alex B., Jul 12 '16 at 06:17
No its not.. I have already used Array.Resize(). Even after doing this I am getting error — Apoorv, Jul 12 '16 at 06:20
Isn't `_with25.NumJobItems - 1` zero ? This is not the start index, this is the length of the array. — Zein Makki, Jul 12 '16 at 06:25
If the size is zero, you can't access element at index 0 (element 1) — Zein Makki, Jul 12 '16 at 06:29
the code in VB is not throwing errors. I dont know why? is Array.Resize() is an alternate to Redim ? — Apoorv, Jul 12 '16 at 06:31

Dehan Wjiesekara · Answer 1 · 2016-07-12T06:32:19.087

1

Why you resize the _with25.JobItems array to size 0 in following line of your code.

Array.Resize(ref _with25.JobItems, _with25.NumJobItems - 1);

then what happen is your array size become zero. when it comes to line

_with25.JobItems[0] = FrontEndEnums.JobDataConcaveEnum.JDBDryData;

which you get the ArrayIndexOutOfBound exception, you can see, you are trying to set a value to zero'th element of an array where there is no elements at all(array of zero size)

remove the Array.Resize(ref _with25.JobItems, _with25.NumJobItems - 1); Or edit the same line as follows Array.Resize(ref _with25.JobItems, _with25.NumJobItems); and see.

edited Jul 12 '16 at 06:32

answered Jul 12 '16 at 06:21

Dehan Wjiesekara

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NullReferenceException was unhandled. Object Reference not set to instance of the object – Apoorv Jul 12 '16 at 06:23
@Apoorv check `Array.Resize(ref _with25.JobItems, _with25.NumJobItems);` – Dehan Wjiesekara Jul 12 '16 at 06:25

score 1 · Accepted Answer · answered Jul 12 '16 at 07:06

In VB array declarations, you specify the last valid index:

'Declare a single-dimension array of 5 values
Dim numbers(4) As Integer

In C# array declarations, you specify the length of the array.

That means that you should always add 1 when converting a VB array declaration to a C# one. So, simply, don't subtract that 1:

Array.Resize(ref _with25.JobItems, _with25.NumJobItems);

score 1 · Answer 3 · answered Jul 12 '16 at 07:07

The problem is that you cannot resize array to size 0, as other answers mentioned already. Also, you need to know that Array size declared in VBscript is 1 more than C#. So make sure that you provide the proper size. Therefore, in your case you cannot blatantly convert _with25.NumJobItems - 1 from VBScript to C# without adjusting the number.

Regarding Array size in VBScript and C#:

VB script:

Dim arr(5)

' Size is 6, and you can access them by arr(0), arr(1), ... arr(5)
C#

MyType[] arr = new MyType[5];

// Size is 5, and you can access them by arr[0], arr[1], ... arr[4]

MakePeaceGreatAgain · Answer 4 · 2016-07-12T07:13:29.727

0

You won´t need to use Array.Resizeat all, simply copy the content from the existing array into a new one and store this into the original one using Array.CopyTo:

var tmp = with25.JobItems;

with25.JobItems = new MyType[_with25.NumJobItems]; 
tmp.CopyTo(with25.JobItems, 0);

edited Jul 12 '16 at 07:13

answered Jul 12 '16 at 06:37

MakePeaceGreatAgain

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No, [`With` blocks](https://msdn.microsoft.com/en-us/library/wc500chb.aspx) are just shorthand for avoiding having to specify the same variable (or variable + chain or property accessors) for multiple statements that interact with the same object. Nothing "transactional" here. – Damien_The_Unbeliever Jul 12 '16 at 07:12

score 0 · Answer 5 · answered Jul 12 '16 at 18:36

Most of the answers are confusing 'ReDim' with 'ReDim Preserve'. For the conversion of a simple 'ReDim', no Array.Resize call is necessary or even recommended - the C# equivalent is just:

public JobTicketConcaveItemsType InitJobTicketConcaveItemsType()
{
    JobTicketConcaveItemsType OutData = new JobTicketConcaveItemsType();
    OutData.NumJobItems = 1;
    OutData.JobItems = new foo[OutData.NumJobItems];
    OutData.JobItems[0] = JobDataConcaveEnum.JDBDryData;
    return OutData;
}

IndexOutOfRange Exception in code converted from VB to C#

5 Answers5