C# System.IndexOutOfRangeException

Question

Im having some problems trying to resolve this C# error:

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************** Exception Text **************
System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at DayZMap.ProcessMemory.CutString(String mystring) in Z:\p\Memory.cs:line 45
   at DayZMap.Map.refreshMap(Object sender, PaintEventArgs e) in Z:\p\Form1.cs:line 517
   at System.Windows.Forms.Control.OnPaint(PaintEventArgs e)
   at System.Windows.Forms.Form.OnPaint(PaintEventArgs e)
   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
   at System.Windows.Forms.Control.OnPrint(PaintEventArgs e)
   at System.Windows.Forms.Control.WmPrintClient(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

The function it is crashing on is:

public string CutString(string mystring)
{
    char[] chArray = mystring.ToCharArray();
    string str = "";
    for (int i = 0; i < mystring.Length; i++)
    {
        if ((chArray[i] == ' ') && (chArray[i + 1] == ' '))
        {
            return str;
        }
        if (chArray[i] == '\0')
        {
            return str;
        }
        str = str + chArray[i].ToString();
    }
    return mystring.TrimEnd(new char[] { '0' });
}

It throws the exception on the line:

if ((chArray[i] == ' ') && (chArray[i + 1] == ' '))

Any advice would be appreciated. Thanks.

when i = mystring.Length-1, i+1 = mystring.Length that is the problem. — cheedep
– cheedep, Commented May 24, 2013 at 18:33

qJake · Accepted Answer · 2013-05-24 18:34:39Z

1

It is very likely that when you are indexing chArray[i + 1], you are exceeding the size of the array.

Take, for example, if chArray has 5 characters, when i is 4 in your loop, it will attempt to access chArray[5] with your code, which is out of bounds (the bounds of the array in that example would be 0-4).

I don't know what you meant for this code to do, but one fix would be to limit your for by one less:

for (int i = 0; i < mystring.Length - 1; i++)

answered May 24, 2013 at 18:34

qJake

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Comments

Yuriy Faktorovich · Accepted Answer · 2013-05-24 18:34:17Z

1

chArray[i + 1] is outside the length of the array, you likely meant to iterate to mystring.Length - 1.

answered May 24, 2013 at 18:34

Yuriy Faktorovich

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Servy · Accepted Answer · 2013-05-24 18:34:06Z

0

On the last iteration of your loop i is the largest valid index of that collection.

You try to access the item at index i + 1. That index doesn't exist.

You can loop up to the second-to-last valid index if you need to access the "next" index in the body of the loop.

answered May 24, 2013 at 18:34

Servy

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Ed Swangren · Accepted Answer · 2013-05-24 18:34:23Z

0

if (... && (chArray[i + 1] == ' '))

When i == myString.Length - 1, that line goes one past the bounds of the string.

answered May 24, 2013 at 18:34

Ed Swangren

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Wolfgang Ziegler · Accepted Answer · 2013-05-24 18:34:38Z

0

If the last character is ' ' you are indexing at an out of bounds positions with chArray[i + 1]

answered May 24, 2013 at 18:34

Wolfgang Ziegler

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Daniel Conde Marin · Accepted Answer · 2013-05-24 18:43:47Z

0

Array indexing in C# starts from 0, and the Length value of the array counts from 1, so a simple fix would be to change:

for (int i = 0; i < mystring.Length; i++)

for:

for (int i = 0; i < mystring.Length - 1; i++)

There are other platforms like Matlab, that indexes arrays counting from 1, so , in there your code could have success!. Cheers!!!

answered May 24, 2013 at 18:43

Daniel Conde Marin

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