Call COM object method with optional parameters.

[Yong Jiang]

I am trying to convert some vb code calling COM oboject
methods to C#. Example shown as follows

Dim Stream As New ADODB.Stream
Call Stream.Open()

Stream.Open has three optional parameters. I am trying to
convert it to C# as shown as follows

ADODB.Stream Stream = null;
Stream = new ADODB.Stream();
Stream.Open();

Somehow, C# does not like leaving paramters blank. I don't
know how to get around of it. Any help will be
appreciated.

[Nicholas Paldino [.NET/C# MVP]]

Yong,

C# does not support optional parameters, so you are going to have to
pass in a value of Missing for all of the parameters that you do not want to
pass in. In order to do that, you will want to do the following:

// Get a missing value.
object pobjMissing = System.Reflection.Missing.Value;

// Make the call.
ADODB.Stream pobjStream = new ADODB.Stream();
pobjStream.Open(pobjMissing, pobjMissing, pobjMissing, pobjMissing,
pobjMissing);

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Yong Jiang" <yj****@yahoo.com> wrote in message
news:03****************************@phx.gbl...

I am trying to convert some vb code calling COM oboject
methods to C#. Example shown as follows

Dim Stream As New ADODB.Stream
Call Stream.Open()

Stream.Open has three optional parameters. I am trying to
convert it to C# as shown as follows

ADODB.Stream Stream = null;
Stream = new ADODB.Stream();
Stream.Open();

Somehow, C# does not like leaving paramters blank. I don't
know how to get around of it. Any help will be
appreciated.

[Yong Jiang]

I appreciate your help.

Now I got the following error messages.

Argument '2': convert from 'object'
to 'ADODB.ConnectModeEnum'
Argument '3': convert from 'object'
to 'ADODB.StreamOpenOptionEnum
Argumetn '4': connot convert from 'object' to 'string'
Argumetn '5': connot convert from 'object' to 'string'

After I changed it to the following to make complier happy

Stream.Open(objMissing, (ADODB.ConnectModeEnum)
objMissing, (ADODB.StreamOpenOptionsEnum) objMissing,
(string) objMissing, (string) objMissing);

I got runtime errors: Specified cast is not valid.

Once again. Thank you for the help.

-----Original Message-----
Yong,

C# does not support optional parameters, so you are going to have topass in a value of Missing for all of the parameters that you do not want topass in. In order to do that, you will want to do the following:
// Get a missing value.
object pobjMissing = System.Reflection.Missing.Value;

// Make the call.
ADODB.Stream pobjStream = new ADODB.Stream();
pobjStream.Open(pobjMissing, pobjMissing, pobjMissing, pobjMissing,pobjMissing);

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Yong Jiang" <yj****@yahoo.com> wrote in message
news:03****************************@phx.gbl...

I am trying to convert some vb code calling COM oboject
methods to C#. Example shown as follows

Dim Stream As New ADODB.Stream
Call Stream.Open()

Stream.Open has three optional parameters. I am trying to convert it to C# as shown as follows

ADODB.Stream Stream = null;
Stream = new ADODB.Stream();
Stream.Open();

Somehow, C# does not like leaving paramters blank. I don't know how to get around of it. Any help will be
appreciated.

.

[Michael Culley]

These parameter are optional params but not variants. You will need to pass in an empty string (string.Empty i think) for params 4
and 5 and use the correct enum for 2 and 3. Only param 1 is a variant.

--
Michael Culley
"Yong Jiang" <yj****@yahoo.com> wrote in message news:0e****************************@phx.gbl...

I appreciate your help.

Now I got the following error messages.

Argument '2': convert from 'object'
to 'ADODB.ConnectModeEnum'
Argument '3': convert from 'object'
to 'ADODB.StreamOpenOptionEnum
Argumetn '4': connot convert from 'object' to 'string'
Argumetn '5': connot convert from 'object' to 'string'

After I changed it to the following to make complier happy

Stream.Open(objMissing, (ADODB.ConnectModeEnum)
objMissing, (ADODB.StreamOpenOptionsEnum) objMissing,
(string) objMissing, (string) objMissing);

I got runtime errors: Specified cast is not valid.

Once again. Thank you for the help.

-----Original Message-----
Yong,

C# does not support optional parameters, so you are

going to have to

pass in a value of Missing for all of the parameters that

you do not want to

pass in. In order to do that, you will want to do the

following:

// Get a missing value.
object pobjMissing = System.Reflection.Missing.Value;

// Make the call.
ADODB.Stream pobjStream = new ADODB.Stream();
pobjStream.Open(pobjMissing, pobjMissing, pobjMissing,

pobjMissing,

pobjMissing);

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Yong Jiang" <yj****@yahoo.com> wrote in message
news:03****************************@phx.gbl...

I am trying to convert some vb code calling COM oboject
methods to C#. Example shown as follows

Dim Stream As New ADODB.Stream
Call Stream.Open()

Stream.Open has three optional parameters. I am trying to convert it to C# as shown as follows

ADODB.Stream Stream = null;
Stream = new ADODB.Stream();
Stream.Open();

Somehow, C# does not like leaving paramters blank. I don't know how to get around of it. Any help will be
appreciated.

.

[Yong Jiang]

After I used the following statement

Stream.Open(objMissing,
ADODB.ConnectModeEnum.adModeUnknown,
ADODB.StreamOpenOptionsEnum.adOpenStreamUnspecifie d,
string.Empty, string.Empty)

it seems to work fine. I can not use empty string for the
second parameter and third parameter.

Thank you for the help. It is very helpful. Have a very
nice thanks giving.

Yong

-----Original Message-----
These parameter are optional params but not variants. You will need to pass in an empty string (string.Empty i
think) for params 4and 5 and use the correct enum for 2 and 3. Only param 1 is a variant.
--
Michael Culley
"Yong Jiang" <yj****@yahoo.com> wrote in message

news:0e****************************@phx.gbl...

I appreciate your help.

Now I got the following error messages.

Argument '2': convert from 'object'
to 'ADODB.ConnectModeEnum'
Argument '3': convert from 'object'
to 'ADODB.StreamOpenOptionEnum
Argumetn '4': connot convert from 'object' to 'string'
Argumetn '5': connot convert from 'object' to 'string'

After I changed it to the following to make complier happy
Stream.Open(objMissing, (ADODB.ConnectModeEnum)
objMissing, (ADODB.StreamOpenOptionsEnum) objMissing,
(string) objMissing, (string) objMissing);

I got runtime errors: Specified cast is not valid.

Once again. Thank you for the help.

>-----Original Message-----
>Yong,
>
> C# does not support optional parameters, so you are

going to have to

>pass in a value of Missing for all of the parameters that

you do not want to

>pass in. In order to do that, you will want to do the

following:

>
>// Get a missing value.
>object pobjMissing = System.Reflection.Missing.Value;
>
>// Make the call.
>ADODB.Stream pobjStream = new ADODB.Stream();
>pobjStream.Open(pobjMissing, pobjMissing, pobjMissing,

pobjMissing,

>pobjMissing);
>
> Hope this helps.
>
>
>--
> - Nicholas Paldino [.NET/C# MVP]
> - mv*@spam.guard.caspershouse.com
>
>"Yong Jiang" <yj****@yahoo.com> wrote in message
>news:03****************************@phx.gbl...
>> I am trying to convert some vb code calling COM

oboject >> methods to C#. Example shown as follows
>>
>> Dim Stream As New ADODB.Stream
>> Call Stream.Open()
>>
>> Stream.Open has three optional parameters. I am

trying to

>> convert it to C# as shown as follows
>>
>> ADODB.Stream Stream = null;
>> Stream = new ADODB.Stream();
>> Stream.Open();
>>
>> Somehow, C# does not like leaving paramters blank. I

don't

>> know how to get around of it. Any help will be
>> appreciated.
>>
>
>
>.
>

.