Can't create delegate for DataAdapater.Ro wUpdated event (reflection)

[Tim Werth]

I am trying to use reflection to add an event handler for the RowUpdated
event of the OracleDataAdapt er object (ODP.NET), but the same thing can be
said for SqlDataAdapter if you only use reflection. The code I supplied is
based on the SqlDataAdapter with reflection.

The error occurs when trying to create the delegate that will be passed in
to EventInfo.AddEv entHandler. I get the following error:
An unhandled exception of type 'System.Argumen tException' occurred in
mscorlib.dll
Additional information: Error binding to target method.
The binding problem is with the second parameter to the event handler. It
is of type SqlRowUpdatedEv entArgs. Again, in reality, I am trying to use
ODP.NET via reflection. So, in this example, I am not referencing the
System.Data or System.Data.Cli ent namespace directly.

Without referencing the namespace, how would one declare a delegate's method
that has a parameter type that exists in a namespace not being referenced
(does that make sense?)?

I have included some sample code to illustrate the problem. The first
CreateDelegate will succeed with the using System.Data* lines *not*
commented out because you can use the SqlRowUpdatedEv entArgs parameter. If
you comment out the "using System.Data" and "using System.Data.Sql Client"
lines, how do you create the delegate?

Again, I am illustrating my problem here using Sql types, because not
everyone has ODP.NET installed.

Tim

using System;

using System.Reflecti on;

// TAKE THE FOLLOWING TWO LINES OUT TO DEPEND SOLELY ON REFLECTION

using System.Data;

using System.Data.Sql Client;

namespace ReflectionEvent Test

{

class Class1

{

[STAThread]

static void Main(string[] args)

{

CreateSqlDelega te();

}

static public void CreateSqlDelega te()

{

Module systemData = GetSystemDataMo dule();

Type t = systemData.GetT ype( "System.Data.Sq lClient.SqlData Adapter" );

object sqlDAObj = Activator.Creat eInstance( t );

EventInfo ei = t.GetEvent( "RowUpdated " );

// This one works because the second parameter in the handler is of type
SqlRowUpdatedEv entArgs

Delegate d1 = Delegate.Create Delegate( ei.EventHandler Type, typeof(
Class1 ), "rowUpdated_Par amIsProperSql" );

// These other three produce the following error:

//

// An unhandled exception of type 'System.Argumen tException' occurred in
mscorlib.dll

//

// Additional information: Error binding to target method.

// Causes error

Delegate d2 = Delegate.Create Delegate( ei.EventHandler Type, typeof(
Class1 ), "rowUpdated_Par amIsObject" );

// Causes error

Delegate d3 = Delegate.Create Delegate( ei.EventHandler Type, typeof(
Class1 ), "rowUpdated_Par amIsBaseClass" );

// Causes error

Delegate d4 = Delegate.Create Delegate( ei.EventHandler Type, typeof(
Class1 ), "rowUpdated_Par amIsIntPtr" );

}

// THIS WON'T COMPILE WHEN YOU TAKE THE using System.Data* LINES OUT AT THE
TOP

static private void rowUpdated_Para mIsProperSql(ob ject sender,
SqlRowUpdatedEv entArgs e)

{

}

static private void rowUpdated_Para mIsObject(objec t sender, object
oraRowUpdEventA rgs)

{

}

// SqlRowUpdatedEv entArgs is derived from
System.Data.Com mon.RowUpdatedE ventArgs

static private void rowUpdated_Para mIsBaseClass(ob ject sender,
System.Data.Com mon.RowUpdatedE ventArgs e)

{

}

static private void rowUpdated_Para mIsIntPtr(objec t sender, System.IntPtr e)

{

}

static public Module GetSystemDataMo dule()

{

Assembly assembly = null;

Module module = null;

string strongName = "System.Dat a, PublicKeyToken= b77a5c561934e08 9,
Culture=neutral , Version=1.0.500 0.0";

// Load the assembly

assembly = Assembly.Load( strongName );

// Get the module

module = assembly.GetMod ule( "System.Data.dl l" );

return module;

}

}

}

[Kevin Yu [MSFT]]

Hi Tim,

First of all, I would like to confirm my understanding of your issue. From
your description, I understand that you cannot create a delegate throw
reflection. If there is any misunderstandin g, please feel free to let me
know.

Based on my research, SqlRowUpdatedEv entArgs contains enumeration values
StatementType. As this is not supported by current .NET Framework with
CreateDelegate, we cannot use it.

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[Tim Werth]

Kevin,

Thanks for the reply, and if you say it can't be done because of a member of
SqlRowUpdatedEv entArgs, I'll accept that. But, in general, I am still
curious as to the resolution of my problem in generic terms. Let me present
my problem another way without Sql or ODP.NET data types.

Suppose I have object O with and event E that are defined in a module M that
I am referencing in my code via reflection. M also defines object A which
is an argument to E. At compile-time, how can I have written code that will
create a delegate that uses A which the compiler knows nothing about?

Is there a way to bind the event delegate to a method with generic arguments
(object?) which, once called by the event, the method uses reflection to
work with the generic arguments (object?) to access their
properties/methods?

I noticed when using the reference that defines SqlRowUpdatedEv entHandler
that it has an overloaded constructor. When adding a RowUpdated event with
System.Data.Cli ent properly referenced, the code looks something like this:

SqlDataAdapter sda = new SqlDataAdapter( .....);

sda.RowUpdated += new SqlRowUpdatedEv entHandler(sda_ RowUpdated );

private static void sda_RowUpdated( object sender, SqlRowUpdatedEv entArgs e)

{

}
But if you put your cursor anywhere in between the parentheses of the
SqlRowUpdatedEv entHandler constructor and hit Ctrl-Shift-Space to bring up
IntelliSense, you can walk through its two constructors. The first
constructor takes a single argument like the code above illustrates, but the
second constructor takes two arguments, "object object, System.IntPtr
method".

Could the second constructor somehow be used when using reflection to define
the delegate?

Tim

[Kevin Yu [MSFT]]

Hi Tim,

As far as I know, currently, we don't have a workaround. Since you can use
another overload of constructor to create the delegate the reference to the
argument is still a SqlRowUpdatedEv entArgs object which contains a
enumeration member which is not supported. Based on my research, the only
way to overcome this is make the enumeration value to be an integer. Sorry
for the inconvenience.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[Tim Werth]

Kevin,

Thank you for the information.

Tim