Unable to cast object of type 'System.Single[*]' to type 'System.Single[]'

Question

Hi,

Would you please help? I have been struggling for two weeks without any success. I try to convert System._COMObject Type to Array type. It worked in VS2008 however when I change to VS2010 it doesn't.

int[] myLengthsArray = new int[1] { nMem };
int[] myBoundsArray = new int[1] { 1 };

myDs = Array.CreateInstance(typeof(double), myLengthsArray, myBoundsArray);//Depth D
Array myDs;

private void PopulateArrays(Multiframe.SectionList mySectionList)
{
        myDs = (Array)mySectionList.D;
}

I also try Array.ConvertAll but that didn't work either

myDs = Array.ConvertAll<object, double>(testdata, new Converter<object, double>(ConvertIntToString));
private double ConvertIntToString(object iData)
{
        double cData = Convert.ToDouble(iData);
        return cData;
}

Thanks

Rob

Maxime p · Answer

I registred an account juste for this answer. Thank you for you post, that helped me !

Vulpes · Answer

That's a relief as I was running out of suggestions :) The compile type of mySectionList.D is interesting. I think I'm right in saying that where COM methods return a variant, this is now showing up in C# 4.0 as the new 'dynamic' type which defers the checking of the actual type until runtime. Casting first to object does the same thing and must therefore be the reason why it now works.

Phung · Answer

Vulpes: private void FillArrays(Multiframe.SectionList mySectionList) { myDs = (Array)(object)mySectionList.D; } It works... THANK YOU. Object Browser show the type of mySectionList.D at runtime is dynamic{float[]}

Vulpes · Answer

One other thought. If you check the properties for the Multiframe COM dll in the project's references and it gives 'True' for Embed Interop Types, then I'd try changing it to 'False'. Embedding is a new (and, beneath the surface, extremely complex) feature in .NET 4.0 and it wouldn't be surprising if it didn't work properly with some older COM dlls.

Vulpes · Answer

Hmm, puzzling to say the least :-/ With no great confidence, I'd try casting to object before you cast to array: private void FillArrays(Multiframe.SectionList mySectionList) { myDs = (Array)(object)mySectionList.D; } If it's no better, what is the object browser showing the compile time type of Multiframe.SectionList.D to be?

Phung · Answer

Hi, Apologies for the confusion. I'm trying to connect to Multiframe via COM. The COM object (Multiframe.SectionList mySectionList) returns a single dimension array of type float with the first element of the array having index 1 rather than 0. This is why I have to create an array with first index being 1 rather than 0 (see CreateArray) Class SectionListArray { Array myDs; public SectPropArray(){} ~SectPropArray(){} public void Add(ref Multiframe.SectionList mySectionList) { int nMem = myMemberList.Count; CreateArrays(nMem); FillArrays(mySectionList); } private void CreateArrays(int nMem) { int[] myLengthsArray = new int[1] { nMem }; int[] myBoundsArray = new int[1] { 1 }; myDs = Array.CreateInstance(typeof(double), myLengthsArray, myBoundsArray);//Depth D } private void FillArrays(Multiframe.SectionList mySectionList) { myDs = (Array)mySectionList.D; } } When I converted from VS2008 to VS2010 there were no warnings or errors. The exact code executed perfectly in VS2008. The error message is Unable to cast object of type 'System.Single[*]' to type 'System.Single[]. Vulpes: I tried your code too but the error pops up at line Array temp = (Array)mySectionList.D; It is a runtime error not a compiling error. I upgraded the code to VS2010 to utilise Parallel Programming features in .NET 4 but I may have to revert back to VS2008 until the problem is sorted. Please assist! Thank you Phung

Vulpes · Answer

It's probably a runtime error because the compiler does not know the underlying type of mySectionList.D. There has been some tinkering with COM interop in VS 2010 (.NET 4.0) which seems to be producing the odd breaking change with previous code. However, AFAIK, you never have been able to cast between single dimensional arrays with different lower bounds - curiously you can convert between multi-dimensional arrays - so I'm puzzled why it should apparently work in VS 2008.

Sam Hobbs · Answer

Well I keep telling people to put everything relevant in the body. The subject should only be used to help others to decide whether to read the question. I honestly did not know that the subject had the error message. Also, I don't know if that is a compile-time error or an execution error. I hope the problem is solved by copying the data but if that is what is needed then I don't understand why that was not needed for VS 2008. My suspicion is that there is a problem with the COM object or whatever it is.

Vulpes · Answer

The error message is in the question title, Sam, but I'm struggling to reconcile it with the code that Rob has posted. The error message is telling you, Rob, that you can't convert a single dimensional float array with an unknown lower bound to a single dimensional float array with a lower bound of zero. If this is in fact what you're trying to do, then you'll need to copy the elements using GetValue() because a cast won't work. I imagine mySectionList.D is a System.__COMObject which actually represents a single dimensional float array with a lower bound of 1. So, if you want to copy that to a zero-based single dimensional double array (I notice you're not using float), I'd try the following code: Array temp = (Array)mySectionList.D; double[] myDs = new double[temp.GetLength(0)]; for(int i = 1; i { myDs[i - 1] = (float)temp.GetValue[i]; }

Sam Hobbs · Answer

When you converted to VS 2010 it did a conversion; what errors did it show? Don't ignore errors such as that. Whenever you say something doesn't work it is nearly always necessary to be specific. Please be specific about what the error is or what does not work or whatever. Also, where does the System._COMObject Type come from? Also, are you totally sure that your program is checking for errors? Have you used the debugger to ensure that there is valid data?

Unable to cast object of type 'System.Single[*]' to type 'System.Single[]'

Answers (10)