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Asked: 2026-05-11T05:39:38+00:00

The class mshtml.HTMLDocumentClass in Microsoft.mshtml.dll assembly has a method: public virtual void write(params object[]

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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

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1 Answer

  1. 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.

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