C# Discussion Boards - CodeProject

C# interop with type System.__ComObject?

16-Oct-04 10:13

1.) Look at this: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdatasqlclientsqlconnectionclassconnectiontimeouttopic.asp[^]

2.) The following code ensures that the connection is disposed properly. Also if you have a transaction open and something goes bad the rollback is ensured. Smile | :)

using(SqlConnection con = new SqlConnection())<br />
{<br />
  con.Open();<br />
  // Do work here<br />
}

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

Alex Korchemniy

vista2715-Oct-04 15:01

vista27

15-Oct-04 15:01

is there anything special that needs to be done when interopping with objects of type System.__ComObject? without good docs, how do you know what to cast to if all u got is a C# type object?

Re: C# interop with type System.__ComObject?

Heath Stewart15-Oct-04 15:50

Re: Posting a File on a Form

15-Oct-04 15:50

It greatly depends on what you're doing. All types (doesn't matter which language, BTW) are IDispatch implementations unless you expose an interface differently using different enums for either the InterfaceTypeAttribute<?code> (for interfaces) or <code>ClassInterfaceAttribute (auto-generated class interface; never use auto-generated class interfaces, though).

When you cast an object to a COM-defined interface (attributed with ComImportAttribute) a QueryInterface is actually performed using the interface to which you're trying to cast. This means you have to have some idea of what you're trying to cast, otherwise you can either cast it as IDispatch (if it's a dispatch object) or - at the very least - IUnknown, which honestly gives you anything useful.

As I've told many people, understanding COM interop with .NET well requires that you understand COM well. I would recommend picking up a book on COM programming, as well as a book on COM interop if you need further explanation.

There's also several good articles here on this site that explain bits and pieces, but the bigger pictures requires a deeper understanding of just how COM works and how .NET interop works with (and for) COM.

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

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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Posting a File on a Form

Member 138504915-Oct-04 11:27

Member 1385049

15-Oct-04 11:27

Hello,
I am trying to output a txt file to a Windows form in C# of course. I have coded how to read the file, that is not a problem anymore. And I can outpout it to the console. But I have been unsuccessful on how to output it on a Form instead of a console.
Can anyone help please?

A Newbie in tha block

Alvaro Mendez15-Oct-04 11:41

Alvaro Mendez

15-Oct-04 11:41

Add a control (such as the Label or TextBox) to the form and set its Text property to the contents of the file.

Regards,
Alvaro

Our enemies are innovative and resourceful, and so are we. They never stop thinking about new ways to harm our country and our people, and neither do we. - George W. Bush

Re: Posting a File on a Form

Member 138504915-Oct-04 15:33

Member 1385049

15-Oct-04 15:33

Thank you Alvaro for your response,
I am writing a program that reads records from a file of type txt containing stuffs like item name, quantity and prices. The first step is to simply read the file and output its containt on a windows form. The second step will be to compute the total cost of each item and post it the results on the form. I guess I have figured out how to do this second part ( well, i guess). But I am stuck on the first step.
This is what I have:
I have the class, reading the txt file, called PartFile. This class contains this function that is supposed to read the file (maybe typecast everything to string) and sent it to the Form.

public void ReadFile()
{
string line;
StreamReader file = new StreamReader("MyFile.txt");
while((line = file.ReadLine()) !=null)
//Console.WriteLine(line); ///commented out because I want to write the file to a Form, not Console
file.Close();
}

While reading my C# book I read about a ToString function, how can I implemente it here to read the file as strings?
Is that how I should code this function, is there anything I should do? how should I do it? Please, help me think through this.I got a brain storm now....can't find a way to get to the next level that I feel i can pretty much do. I just need to be able to read the file and post it to a form. I kind feel like i can move forward on my own (maybe) right after.
Thank, and i hope someone will help... Thank you Alvaro

A Newbie In Tha Block

Re: Posting a File on a Form

Alvaro Mendez15-Oct-04 21:27

Alvaro Mendez

15-Oct-04 21:27

Do this instead:

StreamReader file = new StreamReader("MyFile.txt");<br />
string contents = file.ReadToEnd();<br />
file.Close();

That's it, now you have the whole contents of the file in one string. Add a Label control to your form and do:

label.Text = contents;

Regards,
Alvaro

Our enemies are innovative and resourceful, and so are we. They never stop thinking about new ways to harm our country and our people, and neither do we. - George W. Bush

.NET Remoting Reference

Wender Oliveira15-Oct-04 9:45

Wender Oliveira

15-Oct-04 9:45

I have a class Client (client.cs) that is serializable and a class RemoteMethods (MarshalByRefObject) with a method public static Client getClient(int clientID). Ok... now the question... how to add a "remote" reference to Client class. I want to access this class without need to have the Client's dll on my client side I want to access this referencing it on another machine... This is possible?

Regards....

Wender Oliveira
.NET Programmer

Alex Korchemniy15-Oct-04 10:10

15-Oct-04 10:10

Please clearify...

Wender Oliveira wrote: without need to have the Client's dll on my client side.

And another thing

Wender Oliveira wrote: how to add a "remote" reference to Client class

If you are trying to reference something in the client assembly from the server assembly your design is not right. That class must be in the shared assembly.

Confused | :confused:

Wender Oliveira15-Oct-04 10:15

Wender Oliveira

15-Oct-04 10:15

Sorry... lol
I want to make a new instance of a class that exists only on my remote server... I don't want to copy the dll that has this class inside to my client server...

Wender Oliveira
.NET Programmer

Alex Korchemniy15-Oct-04 10:20

15-Oct-04 10:20

OK. That's more like it. Smile | :)

What you do is you create a library that has that class you want to use in both the client and the server. You then add a reference to the library in both the server and the client.

Another thing. If you want to have the implementation for the code hidden you can create an interface that matches the code (its a good practice to come up with the interface before hand Smile | :)

) and put the interface in the shared library.

Wender Oliveira15-Oct-04 10:24

Wender Oliveira

15-Oct-04 10:24

Thanks Alex... This is what I want to know but not what I want to read. I'm doing like you said and I was hopeful to find another way... like webservice... you just add a web reference and all those classes can be found by vs.net ...

Thanks again...

Wender Oliveira
.NET Programmer

Alex Korchemniy15-Oct-04 10:29

Change the caret color in a textbox

15-Oct-04 10:29

Yeah WS work differently. They use WSDL to describe how the WS works. There is a tool call soapsuds.exe if you are hosting your remoting object using HTTP and Soap you can use it to generate an interface assembly. I've ran across this when getting my MCAD but you'll have to look into it more.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cptools/html/cpgrfsoapsudsutilitysoapsudsexe.asp[^]

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

Alex Korchemniy

ee9903515-Oct-04 7:30

ee99035

15-Oct-04 7:30

How can i change the caret color in a textbox?!! Is it possible?!

Thanks

Re: Change the caret color in a textbox

Alex Korchemniy15-Oct-04 9:47

Re: Change the caret color in a textbox

15-Oct-04 9:47

I'm looking for the same thing. Well not really looking but I need a solution. Dont have time to look Blush | :O

Carl Mercier15-Oct-04 17:13

Carl Mercier

15-Oct-04 17:13

Not sure if it helps... but here's some VB6 code I found on the groups:

http://groups.google.com/groups?hl=en&lr=&safe=off&selm=u5toJi9KBHA.1440%40tkmsftngp07[^]

slow listview refresh

DF_Bandit15-Oct-04 6:49

DF_Bandit

15-Oct-04 6:49

I have a listview in detail mode which I use to display a subset of records from an SQL table. If the user changes the subset parameter I refresh the list with another set of lines.
My problem is that while the original population of the list is very fast (it is done in the dialog's constructor), the refreshes are quite slow - about 10 seconds for a 500 line data set.
I know the problem lies with the listview since if I comment out the listview code, the method executesd quite fast. I have tried:
begin/end update
setting enable=false and then true
setting visible=false and then true
None seem to have more than a small effect (about 10% difference).

Any suggestions?

the method's code:

...<br />
sqlCmd.CommandType = CommandType.StoredProcedure;<br />
SqlDataReader reader = sqlCmd.ExecuteReader();<br />
<br />
lvwLogDays.Items.Clear();<br />
      <br />
while( reader.Read() )<br />
{<br />
	DateTime Date = reader.GetDateTime( reader.GetOrdinal( "LogDate" ) );<br />
	string strTemp = Date.ToString( "MM/dd/yyyy" );<br />
	OpenDayLogData	DayLogData = new OpenDayLogData();<br />
<br />
	ListViewItem item = lvwLogDays.Items.Add( strTemp );<br />
        strTemp = reader["CallLetters"].ToString().Trim();<br />
        item.SubItems.Add( strTemp );<br />
<br />
	strTemp = reader["LogStatus"].ToString().Trim();<br />
        item.SubItems.Add( strTemp );<br />
<br />
	DayLogData.LogID = Convert.ToInt32(reader["DF_LogID"].ToString(), 10);<br />
	DayLogData.LogDayID = Convert.ToInt32(reader["DF_LogDayID"].ToString(), 10);<br />
        item.Tag = DayLogData;<br />
}<br />
...

Heath Stewart15-Oct-04 7:00

15-Oct-04 7:00

Calling ListView.BeginUpdate before clearing and adding items, and ListView.EndUpdate should help performance quite a bit.

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Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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DF_Bandit15-Oct-04 7:10

DF_Bandit

15-Oct-04 7:10

Actually I have the method (and one that follows this method - a sorter) bracketed by BeginUpdate() and EndUpdate() to no avail. As I wrote in the original, there seems to be about a 10% gain by using such a technique.

so the code goes something like this:
lvwLogDays.BeginUpdate();
RefreshList();
SortList();
lvwLogDays.EndUpdate();

Optionally, I have put lvwLogDays.Enabled=false/true bfroe/after the update calls.

Heath Stewart15-Oct-04 8:44

15-Oct-04 8:44

You could also get a pretty good gain if you fetch all records first (say, into a DataSet) and then build your list. This really depends on your wire speed and format, though (whether or not you'll see any gains).

One other thing is to make sure that your ListView doesn't specify a sort already if you're going to sort it later a la SortList. Do one or the other, but not both. Sorting the list after is most often faster when you have a large number of items.

Is the code you use for the first and future operations exactly the same (with the call to Clear), i.e. you're using a DataReader to fetch the rows, etc.?

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Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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DF_Bandit15-Oct-04 9:39

DF_Bandit

15-Oct-04 9:39

Thanks for the help.

I did replace the reader with a load into a DataTable and then 'foreached' out of it - no noticible difference in speed.

I have ensured the listview does not sort. We opted to sort after so we can perform sorts on the various columns if the user clicks a column head.

The method I cliped from (LoadLogList) is used both by the dialog's constructor and then by the refresh method, so it is used in 'first and future operations'. So I call the Clear() when I know the listview's item list is empty. I just moved the clear out of the method - no noticable difference.
I now do this:

lvwLogDays.Enabled=false;<br />
lvwLogDays.BeginUpdate();<br />
lvwLogDays.Items.Clear();<br />
LoadLogList();<br />
Resort( 0 );<br />
lvwLogDays.EndUpdate();<br />
lvwLogDays.Enabled=true;

Heath Stewart15-Oct-04 15:42

15-Oct-04 15:42

Out of curiousity, are you by changing collecting data in a separate thread other than the one the ListView was created? If so, undefined problems can result. In such a case, you need to use Control.Invoke. The SDK documentation gives clear details and examples.

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

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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