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Then you have a problem. Potentially you could solve this by having a series of importers, and then using Inversion of Control to load the appropriate one at runtime.
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Hi,
I have this VB6 code to follow and I'm fairly new to C# but I manage to do most things with my COM object in C# that I used to in VB6, but I just can't get my hand around subscription in C# despite googling for days.
I'm trying to do something like this, but no luck.
------------C#---------------
void SubscribeToEvent()
{
g.OnServiceAccessPerformanceUpdate += new INetMonClientObjNotify_OnServiceAccessPerformanceUpdateEventHandler(g_OnServiceAccessPerformanceUpdate);
}
This is the code in VB6 that works...
------------VB6--------------
Private Sub SetServiceAccessSubscription(SiteID As String, IDList() As Long)
On Error Resume Next
Dim VariantIDList As Variant
VariantIDList = IDList
g_NetMonitor.SetServiceAccessSubscription SiteID, VariantIDList
If Err.Number = 0 Then
PrintLine ("Service Access subscription successfully set.")
Else
Err.Clear
PrintLine ("Failed to set Service Access subscription.")
End If
End Sub
-----------------------------
Anyone care to give me some ideas of how to subscribe to the COM object updates? 
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Assumming the SetServiceAccessSubscription sub has the same signiture as the INetMonClientObjNotify_OnServiceAccessPerformanceUpdateEventHandler delegate, the code should be more along the lines of:
g.OnServiceAccessPerformanceUpdate += new INetMonClientObjNotify_OnServiceAccessPerformanceUpdateEventHandler(SetServiceAccessSubscription);
Note the change in the ...OnServiceAccessPerformanceUpdateEventHandler parameter from g_OnServiceAccessPerformanceUpdate to SetServiceAccessSubscription.
Hope that helps
"You get that on the big jobs."
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Thanks! Great, half way there...
What would the EventHandler sub look like? 
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Don't know but Visual Studio is normally smart enough to autocomplete the statement for you. if you enter
g.OnServiceAccessPerformanceUpdate += Intellisense should automatically display the correct delegate. Hit tab and Intellisense will enter a default name for the subroutine. Hit tab again and a stub with the correct parameters should be created. So normally after you have typed the += symbols, all you need to do is tab, tab.
Hope that makes (intelli) sense
"You get that on the big jobs."
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Thanks but that was what I initially did, and that's when I got the code I've quoted in my first message.
Maybe there's some problem with the "Intelli"-part of Intellisense? Or it might be just me, but I never get an Event. It compiles ok, but still "no action" when subscribed, and this COM object does send a lot of updates...
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Are you sure the COM component is calling the event? The two code snippets you provide are different in their approach to subscribing. Perhaps you need to call SetServiceAccessSubscription from C#, instead of just hooking onto the event?
COM interop can be a bit strange to use because many COM components do not quite work how a .Net person expects.
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BobJanova wrote: Perhaps you need to call SetServiceAccessSubscription from C#, instead of just hooking onto the event?
I'm starting to think that myself. Just have to figure out Variants in C#. 
Thanks!
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I think you can use object, and then use is or GetType to work out what further to do with it.
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So, I am currently writing some software for my job. I am using OLE DB to connect to a Microsoft Office Access 2007 database, where all the data is stored. I have no issues for the most part. However, I have a question concerning null field values when using OleDbDataReader.GetValue/String/Int/DateTime/etc.
Some fields in the database are required. This is no issue because I validate the necessary data in the software before attempting to insert/update records. But what about the fields that are not required by the database? Do I have to use "IsDBNull(ordinal)" for each field before I attempt a GetValue/String/Int/DateTime/etc. Or is there an easier way to go about "looking over" null values?
I have a class, RepairRecord, which stores the information about each record. And as an example, I have a field, Comments, which is not a required field. If I insert a record with no value for Comments all is well. That is, until I attempt to SELECT the record. If I simply use "reader.GetString(11)" and the value is empty I get an InvalidCastException, which I understand. I just need to know if there is a simpler method which I am looking past for dealing with these. The Comments field is not the only field that is optional.
If I am leaving out any important information just let me know.
Tools I am using:
Visual Studio 2010
C# (.NET 4.0)
OLE DB
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For one thing, I never use the Getxxx methods -- they're as useless as the Convert class  .
For another, don't use the ordinal values; use the names -- the order of things could change unexpectedly.
And, what do you do when it is null? Apply a default?
You may want something along the lines of:
System.DateTime somedate = System.DateTime.MinDate ;
if ( reader [ "somedate" ] != System.DBNull.Value )
{
somedate = (System.DateTime) reader [ "somedate" ] ;
}
(I don't feel like testing that right now, so I hope it works. Come on, beer, do your stuff!)
P.S. Oh, and I suppose you could write a generic Extension Method to simplify that for you.
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Oh, thanks for the timely response. :-P I will give that a try as soon as I get back on the project. I knew I was missing something, I just couldn't figure out what. But I haven't had much experience AT ALL with database-driven application development.  So please stick with me, as I am a noob. xD
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That made me wonder about a few things, so here are two questions for you:
1.
I understand if your SQL says "SELECT * FROM ..." you will get the fields either in their table structure order, or in an arbitrary order (which is the same for all practical purposes as someone could change the structure).
However if your SQL says "SELECT A,B,C FROM ...", would reader["A"] and reader[0] not be absolutely equivalent?
2.
If so, it gives another good reason to name the fields explicitly in the SQL statements. And yes, I would still prefer to use the field names as an index, as that improves readability. Would it also negatively affect performance?
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
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Luc Pattyn wrote: would ... not be absolutely equivalent?
I haven't bothered to compare, but I suspect that the overload with the name performs a lookup and then calls the overload with the index -- it would therefore be slower, but easier to read and maintain etc.
P.S. Oh, and don't forget that if you are using stored procedures for your queries , some one may mess with one.
modified on Wednesday, May 18, 2011 11:08 PM
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Yeah, that's what I was thinking. Slower and better looking.
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
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That's how I like my women too.
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Well, obviously, the best of both worlds would be to set some constants above it all, i.e. A=0, B=1,C=2, so Reader["A"] would be the equivalent of Reader[A], and so on.
Almost time to go home. Silliness abounds.
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1. Using index is faster than using names, since using names does an additional index lookup, but it increases readability considerably and is also safer. Imagine a database developer changing your query from something like this
SELECT A,B,C FROM ...
to this
SELECT B,A,C FROM ...
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Luc Pattyn wrote: Would it also negatively affect performance?
This tends to be treated as a micro-optimisation that is completely useless. There is a simple way to get around this performance hit, which is to use the ordinal based value, but use GetOrdinal to retrieve the position of the ordinal based on the field name.
The thing is, you only need to use GetOrdinal once for each field you are interested in - which means that you can use the ordinal in the loop over the reader.
Effectively, your code becomes something like this (with apologies because I'm just typing this off the top of my head in the CP editor):
int customerId = reader.GetOrdinal("CustomerID");
int customerName = reader.GetOrdinal("Name");
while (reader.Read())
{
Customer cust = new Customer(GetValue(reader, customerId), GetValue(reader, customerName));
}
private T GetValue(SqlDataReader dr, int position)
{
if (dr.IsDbNull(position))
return default(T);
return (T)dr[position];
}
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I like it. The rule now is: don't use numeric field indexes ever; use field names directly, unless you can't afford the speed penalty, then use GetOrdinal as per your example (which is safe but somewhat more verbose).
And you could still make that an extension method on DataReader, as PIEBALD suggested.
Thanks Pete.
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
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Luc Pattyn wrote: The rule now is: don't use numeric field indexes ever; use field names directly,
unless you can't afford the speed penalty, then use GetOrdinal as per your
example (which is safe but somewhat more verbose).
Guidelines to live by 
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How to make possible the activation of group-box controls by choosing one of the options in combo-box list?
Best regards
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Look at the documentation first, then come ask questions.
DOCUMENTATION[^]
Looks like OnSelectedItemChanged or OnSelectedValueChanged should work quite well for you.
The best way to accelerate a Macintosh is at 9.8m/sec² - Marcus Dolengo
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Not sure what you mean by activation. I think you may be referring to either enabled or visible. Lets say it's the enabled property of the GroupBox. First you need to catch the SelectedIndexChanged event of the ComboBox, evalutate the selection and determine if the GroupBox should be enabled
private void MyComboBox_SelectedIndexChanged(object sender, EventArgs e)
{
MyGoupbox.Enabled == (MyComboBox.SelectedValue == criteria);
}
Excuse the pseudocode but i think you get the idea
"You get that on the big jobs."
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Hello.
I have a problem. I have two independient forms inside the same project and I want to call a function that is in the form 1 from form 2.
I am using c# for an window application
I have declared in the form 1 the following function:
public void Hola()
{
MessageBox.Show("Hello");
}
But I don´t know how to call from form2
Thank you very much!!
modified on Wednesday, May 18, 2011 11:22 AM
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