Infopath中，自己编写的ActiveX控件，为何不能绑定数据到XML属性节点

转自：http://www.mcse.ms/message1299834.html&highlight=InfopathControl.savestate

I've been recently dealing with this same issue and here's the resolution

I've come to:

1. You can ONLY use Integers, Longs and Strings to represent your data in

InfoPath. I tried stdOLE.Picture, Variant, Byte() and they all won't bind by

default (or at all after many hours of recompiling to test). Why you ask?,

InfoPath is storing the data in an XML document file as node data

(<node>datadatadatadata</node>). Most types of data are using illegal

characters in this context and utf-8 or iso-8859-1 encoding won't solve the

problem, and I'm not quite sure why.

The simple resolution to storing ANY form of binary data is to Base64 encode

the data and return it as a String. Just to be fair here, after talking with

Microsoft about this using Visual Studio .NET and creating a

custom InfoPath form with the SDK should allow for binary data, however the

reason some of us are using ActiveX controls for data representation is

because not everyone working with InfoPath is a programmer, which is what is

expected when using .NET. This process is futher complicated by having to

create custom data schemas for InfoPath in VS .NET. Again, the simple

resolution to storing ANY form of binary data is to Base64 encode the data

and return it as a String.

2. Even though some of the examples lead you to believe that you can have

your own Public Property names, InfoPath's default schema only recognizes

ENABLED and VALUE (just as the examples show, but don't clearly state this as

a condition), so you may have to adjust your code to expose those names, or

use the InfoPath SDK and extend the default schema to accomodate your public

properties, for which I haven't seen any faq's or examples.

One more thing I forgot to mention, you must use the StrConv() function to

convert to and from Unicode data for your string value. Again the reason for

this is you're dealing with XML node data. See example below.

Public Property Get Value() As String 'Needs to be called Value, data needs to be String 'Ignore all Errors or InfoPath will die an Automation Exception death

On Error Resume Next

Set m_oSig = New cSigControl

If m_Signature.Handle Then 'Convert our STDOLE Picture to Base64 encoded string.'Then convert the Base64 string to UniCode and return the value.

Value = StrConv(m_oSig.SetStreamPicture(m_Signature), vbUnicode)

End If

Set m_oSig = Nothing

End Property

Public Property Let Value(vData As String) 'Needs to be called Value, data needs to be string 'Ignore all Errors or InfoPath will die an Automation Exception death

On Error Resume Next

Set m_oSig = New cSigControl

'Convert the incoming string from Unicode, then decode the Base64 encoding

'Stream the Base64 encoding back to STDOLE Picture.

'GetStreamPricture will return true if succussfully converted Base64

stream to IPicture.

If m_oSig.GetStreamPicture(StrConv(vData, vbFromUnicode)) Then

Set m_Signature = m_oSig.UserSignature 'Double checking for validity

If Not m_Signature Is Nothing Then

Set UserControl.Picture = m_Signature

Me.SignDocument = False

PropertyChanged "Value"

End If

End If

UserControl_Paint

UserControl.Refresh

Set m_oSig = Nothing

End Property