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I have a C# WinForms .NET 3.5 application that I need to call a COM DLL written in Visual FoxPro 7. I have added the COM object to the C# project fine, and can

view the objects and its members in the object browser fine.

However when I attempt to call any methods or access any properties from the COM object I get the following exception thrown :

System.AccessViolationException was unhandled Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt. Source=Interop.emscosting StackTrace: at emscosting.ComBaseClass.ShellExecute(String tcItem, String tcAction) ...

Below is some example C# code I am using :

emscosting.ComBaseClass com = new emscosting.ComBaseClass(); com.ShellExecute(file, "TRUE"); <--- The exception is thrown here

Also when I try and access any of the public properties of the COM object in the debugger watch window I get the following appear in the Value column : 'com.DatabaseUserName' threw an exception of type 'System.AccessViolationException'

I am already using this COM object without any issues from other VFP applications, Office applications, and in Javascript/Classic ASP.

Can someone help me resolve this issue please ?

I do have the original VFP source code for the COM still and below is a snippet of the code where I am declaring the public properties, however I am trying to

avoid rewriting the COM DLL if possible!

#If BUILD_AS_COM_OBJECT
Define Class emsCosting As Combase OlePublic
#Else
Define Class emsCosting As Combase
#Endif

CostingsPath = COSTINGS_PATH
Dimension CostingsPath_COMATTRIB[5]
CostingsPath_COMATTRIB[1] = COMATTRIB_NONE
CostingsPath_COMATTRIB[2] = "Contains the path of where the costings get saved" && HelpString
CostingsPath_COMATTRIB[3] = "CostingsPath" && Capitalisation
CostingsPath_COMATTRIB[4] = "String" && Property Type
CostingsPath_COMATTRIB[5] = 0 && Number of parameters

CostingsMaster = COSTINGS_MASTER
Dimension CostingsMaster_COMATTRIB[5]
CostingsMaster_COMATTRIB[1] = COMATTRIB_NONE
CostingsMaster_COMATTRIB[2] = "Contains the filename of the costings master (usually costings.xls)" && HelpString
CostingsMaster_COMATTRIB[3] = "CostingsMaster" && Capitalisation
CostingsMaster_COMATTRIB[4] = "String" && Property Type
CostingsMaster_COMATTRIB[5] = 0 && Number of parameters

Function SetCostingsPath(tcPath As String) As VOID HelpString "This is a test function"
    CostingsPath = tcPath
EndFunc

Function TestFunctionNoParam() AS String HelpString "This is a helpstring"
    Return "\\TEST\ContractReviewCostings\"
EndFunc

......

NOTE: Both the two test functions defined above fail with the exception System.AccessViolationException

Chris Crowhurst
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1 Answers1

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You have to compile your .Net Application for x86, if you have a x64 system. When you compile it with "Any CPU" or "x64", you can not access the x32 FoxPro-DLL.

user2219063
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