MS Word Automation in C# – Unable to cast object of type ‘System.String[*]’ to type ‘System.String[]’

calendar_today Asked Aug 16, 2011
thumb_up 7 upvotes
history Updated April 16, 2026

Question posted 2011 · +9 upvotes

I use this code to get a String array of headings used in a MS Word 2007 document (.docx):

dynamic arr = Document.GetCrossReferenceItems(WdReferenceType.wdRefTypeHeading);

Using the debugger, I see that arr is dynamically assigned a String array with titles of all my headings in the document (about 40 entries). So far so good.

Then, I want to access the strings, but no matter how I do it, I get the following exception:

InvalidCastException: 
           Unable to cast object of type 'System.String[*]' to type 'System.String[]'.

I have tried different ways of accessing the strings:

By index:

String arr_elem = arr[1];

By casting to an IEnumerable:

IEnumerable list = (IEnumerable)arr;

By using a simple foreach loop:

foreach (String str in arr)
{
   Console.WriteLine(str);
}

However, no matter what I try, I always end up with the same exception as shown above.

Can anyone explain what I am missing here / what I am doing wrong? And especially String[*] – what does it mean?

Accepted answer +7 upvotes

string[] is a vector – a 1-d, 0-based array. string[*], however, is a regular array that just happens to have one dimension. Basically, you are going to have to handle it as Array, and either copy the data out, or use the Array API rather than the string[] API.

This is the same as the difference between typeof(string).MakeArrayType() (the vector) and typeof(string).MakeArrayType(1) (a 1-d non-vector).

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