Error when calling msi native apis

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Mike Faltys - 26 May 2004 00:16 GMT

The code snippet below was simplified from a much larger application. I can run against several other functions in Msi.dll without problems. However, I am running into a problem when executing against the MsiGetSummaryInformation function. I get the exception "Object reference not set to an instance of an object" when calling the function. I have tried everything that I can think of. What am I missing?

Thanks
Mik

using System
using System.Runtime.InteropServices

namespace SimpleTestIns

    /// <summary
    /// Summary description for Class1
    /// </summary
    class Class

        /// <summary
        /// The main entry point for the application
        /// </summary
        ///

        [DllImport("msi.dll")
        private static extern uint MsiGetSummaryInformation(ulong dbhandle,string path,uint updateCount,ref ulong infoHandle)

        public void Test(

            ulong aHandle = 0
            uint rc = MsiGetSummaryInformation(0,null,19,ref aHandle)
            Console.WriteLine("Executed successfully.")


        [STAThread
        static void Main(string[] args

            tr

                Class1 c1 = new Class1()
                c1.Test()

            catch(Exception e

                Console.WriteLine("\r\n\r\n ERROR MESSAGE: "+e.Message+"\r\n\r\n"+e.StackTrace)




ERROR

ERROR MESSAGE: Object reference not set to an instance of an object

at SimpleTestInst.Class1.MsiGetSummaryInformation(UInt64 dbhandle, String pa
h, UInt32 updateCount, UInt64& infoHandle
at SimpleTestInst.Class1.Test() in d:\hh3-new\rsr-rel1\ingen\build\net\test\
estmsi\simpletestinst\class1.cs:line 2
at SimpleTestInst.Class1.Main(String[] args) in d:\hh3-new\rsr-rel1\ingen\bu
ld\net\test\testmsi\simpletestinst\class1.cs:line 3

Reply to this Message

Phil Wilson - 26 May 2004 01:19 GMT

What happens if you actually give it a string that it's expecting instead of
a null?

Signature

Phil Wilson [MVP Windows Installer]
----

> The code snippet below was simplified from a much larger application. I can run against several other functions in Msi.dll without problems.

However, I am running into a problem when executing against the
MsiGetSummaryInformation function. I get the exception "Object reference
not set to an instance of an object" when calling the function. I have
tried everything that I can think of. What am I missing?

> Thanks,
> Mike
[quoted text clipped - 50 lines]
> at SimpleTestInst.Class1.Main(String[] args) in d:\hh3-new\rsr-rel1\ingen\bui
> ld\net\test\testmsi\simpletestinst\class1.cs:line 33

Reply to this Message

Mike Faltys - 26 May 2004 01:31 GMT

Same error. I have tried to pass the location of the msi database. I have also attempted to change the string to an uint and pass 0 and also the valid memory location of a string. All have yielded the "Object reference not set to an instance of an object".

Thanks,
Mike

Reply to this Message

Phil Wilson - 26 May 2004 01:46 GMT

Ok, it's not the string, it's that the handles need to be IntPtr, and you
haven't allocated one for the first parameter:

[DllImport("msi")]
private static extern uint MsiGetSummaryInformation(IntPtr dbhandle,string
path,uint updateCount,ref IntPtr infoHandle);
public void Test()
{
IntPtr inh = new IntPtr(0); // Should be a real handle even if it's empty
IntPtr aHandle = IntPtr.Zero;
uint rc = MsiGetSummaryInformation(inh,"this",19,ref aHandle); // gets 1620
when you don't have the file path
Console.WriteLine("Executed successfully.");
}

Signature

Phil Wilson [MVP Windows Installer]
----

> Same error. I have tried to pass the location of the msi database. I have also attempted to change the string to an uint and pass 0 and also the

valid memory location of a string. All have yielded the "Object reference
not set to an instance of an object".

> Thanks,
> Mike

Reply to this Message

MikeFaltys - 27 May 2004 01:46 GMT

Thanks, that worked.

Reply to this Message

Error when calling msi native apis

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