The class mshtml.HTMLDocumentClass in Microsoft.mshtml.dll assembly has a method:
public virtual void write(params object[] psarray);
Avoiding the real question for a moment, what code would you use to call write()? Would you use:
String html = "<html><body>Hello, world!</body></html>";
mshtml.HTMLDocumentClass doc;
...
doc.write(html);
or would you use:
String html = "<html><body>Hello, world!</body></html>";
mshtml.HTMLDocumentClass doc;
...
object[] params = new Object[1];
params[0] = html;
doc.write(params);
Because both of those throw an exception. (Type mismatch. 0x80020005)
The HTMLDocumentClass.write method actually comes from IHTMLDocument2 interface, which is documented as:
IHTMLDocument2::write Method
Writes one or more HTML expressions to a document in the specified window.
Syntax
HRESULT write( SAFEARRAY *psarray );Parameters
psarray
[in] A **BSTR** that specifies the text and HTML tags to write.
So in reality the write method needs a pointer to a SAFEARRAY, even though Microsoft's Microsoft.mshtml interop assembly define the write method as taking a regular array:
public virtual void write(params object[] psarray);
Ignoring the mshtml interop declaration, i have to construct a SAFEARRAY object (verses an object array), fill it with a BSTR string (verses a String), and stuff it into a parameter that must be an object array.
Note: i'm unsure of the meaning of the params keyword. It is used to indicate a variable number of parameters.
Does that mean that it can take multiple array parameters?
object[] array1 = new Object[1];
array1 [0] = alpha;
object[] array2 = new Object[1];
array2 [0] = bravo;
object[] array3 = new Object[1];
array3 [0] = charlie;
object[] array4 = new Object[1];
array4 [0] = delta;
doc.write(array1, array2, array3, array4);
Or is object[] the method in which multiple parameters are passed, and you must literally create an array?
object[] params = new Object[4];
params[0] = alpha;
params[1] = bravo;
params[2] = charlie;
params[3] = delta;
doc.write(params);
Or is the array[] just a decoy, and really you pass:
doc.write(alpha, bravo, charlie, delta);
When i originally used this code, from a native Win32 app, the BSTR was placed inside a SAFEARRAY. In IDispatch based automation, everything is inside an array. In this case the late binding code:
doc.write(html);
was converted by the compiler into a SAFEARRAY, where the zero-th element contains a BSTR string (which is a length prefixed unicode string).
My problem becomes one of trying to construct a SAFEARRAY, converting a String into a BSTR, placing the BSTR into the zero-th element of the SAFEARRAY, and passing a variable that contains a SAFEARRAY to one that only accepts an object array (object[]).
This is the real question: how to create a BSTR SAFEARRAY?
Microsoft.mshtml
C:\Program Files\Microsoft.NET\Primary Interop Assemblies\Microsoft.mshtml.dll
The declaration for the write method on the IHTMLDocument2 interface created by TLBIMP/VS.NET is incorrect. It should be:
void Write([In, MarshalAs(UnmanagedType.SafeArray)] object[] psarray);
You will have to define this interface in code and then use that.