Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

Last post 05-13-2004 2:11 PM by cnahr. 3 replies.

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03-23-2004 4:08 PM

kblaney
Joined on 03-23-2004
Posts 3
Points 100

Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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My CodeSmith-generated hashtable throws an exception in a case when Hashtable does not.

When I use CodeSmith to generate a StringCarHashtable class where the keys are of type string and the values are of type Car (a class), the following code throws an ArgumentException.

StringCarHashtable stringCarHashtable = new StringCarHashtable();
string[] stringArray = new string[ stringCarHashtable.Keys.Count ];
stringCarHashtable.Keys.CopyTo( stringArray, 0 );

When I replace StringCarHashtable with Hashtable, no exception is thrown.

The exception throw when StringCarHashtable is used is as follows:

Unhandled Exception: System.ArgumentException: Argument must be less than array length.
Parameter name: arrayIndex
at ConsoleApplication1.StringCarHashtable.CheckTargetArray(Array array, Int32 arrayIndex) in d:\visualstudioprojects\consoleapplication1\class3.cs:line 2443

Kyle Blaney

Post Points: 90

03-23-2004 6:00 PM In reply to

kblaney
Joined on 03-23-2004
Posts 3
Points 100

RE: Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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I believe this problem can be fixed by changing the implementation of the CheckTargetArray method in Hashtable.cst as follows:

Change this line:

if (arrayIndex >= array.Length)
throw new ArgumentException(
"Argument must be less than array length.", "arrayIndex");

to the following:

if ((arrayIndex >= array.Length) &&
((arrayIndex != 0) || (array.Length != 0)))
throw new ArgumentException(
"Argument must be less than array length.", "arrayIndex");

Kyle Blaney

Post Points: 5

03-23-2004 7:02 PM In reply to

ejsmith
Joined on 12-27-2002
Dallas, TX USA
Posts 2,185
Points 873,825

RE: Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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Kyle,

I will pass this on to Chris. He is the maintainer of these collection templates.

Thanks,
Eric J. Smith

Eric J. Smith
CodeSmith Tools, LLC
Chief Software Architect

Post Points: 5

03-29-2004 5:46 PM In reply to

kblaney
Joined on 03-23-2004
Posts 3
Points 100

RE: Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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Note that the same problem occurs with a CodeSmith generated ArrayList. For example, the following code throws an ArgumentException when it should not:

IntArrayList intArrayList = new IntArrayList();
int[] intArray = new int[0];
intArrayList.CopyTo( intArray );

This problem can be fixed by making the same modifications to the CheckTargetArray method as detailed above.

Post Points: 5

03-30-2004 5:22 PM In reply to

cnahr
Joined on 06-03-2003
Posts 105
Points 2,275

RE: Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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Sorry for the late reply, I'm rather busy these days and won't be able to produce a fix right away.

Actually I was a bit doubtful at first if a fix was needed at all. CopyTo(array, index) is an ICollection method whose MSDN documentation clearly states that it SHOULD throw an ArgumentException if "index is equal to or greater than the length of array". If array is empty, an index of zero is illegal according to that rule.

So you might argue that the template is correct and the Microsoft class is wrong!

However, you have a good point with ArrayList.CopyTo(array). This one shouldn't throw if array is empty as long as the ArrayList is empty, too.

Seeing that I'll have to fix this anyway I'll reproduce Microsoft's undocumented ICollection.CopyTo behavior as well, in all the templates, as soon as I get around to it.

Post Points: 5

05-13-2004 2:11 PM In reply to

cnahr
Joined on 06-03-2003
Posts 105
Points 2,275

RE: Hashtable.Keys.CopyTo() when hashtable is empty throws ArgumentException

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Fixed in the latest version 1.5.1 for all templates. Thanks for reporting!

Post Points: 5

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