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So, I posted over on the MS as.net forums, but I have to wait for moderator approval for the post to show, and frankly - I'd rather not wait.
I've been googling all over the net and not found an answer that I can completely understand -- heck I'm not even sure I have been googling the right terms.
I need to pass the contents of a DataSet to an ImageButton EventHandler function. The code I have right now errors cuz I believe the standard EventHandler doesn't allow arguments. I found some info on custom EventHandlers, but I don't really understand how to implement them. Here is the pertinenet code:
C# Script tag code:
<br />
public void exportClick(DataSet dat)<br />
{ <br />
DataTable dt = dat.Tables[0];<br />
DateTime dateStamp = DateTime.Now;<br />
string file = dateStamp.Hour.ToString() + dateStamp.Minute.ToString() + dateStamp.Second.ToString();<br />
CreateCSVFile(dt, Server.MapPath("/csv_export/export"+file+".csv"));<br />
}<br />
sql = "SELECT......";<br />
dat=readDb(sql);<br />
<br />
ImageButton ib = new ImageButton();<br />
ib.ID = "exportButton";<br />
ib.ImageUrl = "./img/export.png";<br />
ib.Width = 110;<br />
ib.Height= 25;<br />
ib.AlternateText="Export to CSV";<br />
ib.Click += new EventHandler(exportClick(dat));<br />
Panel1.Controls.Add(ib);<br />
And the HTML:
<br />
<body><br />
<form runat="server"><br />
......<br />
<asp:panel id="Panel1" runat="server" height="25px" horizontalalign="right" /><br />
......<br />
</form><br />
</body><br />
So ideally what should happen is that the user clicks on ImageButton "ib", which fires the exportClick(dat) function and a CSV file is created from the DataSet "dat". If I can get this working, I have code to fire a file download of the CSV that will get stuffed in as well, but I deal with that once I have a CSV.
Thanks in advance!
modified on Friday, January 11, 2008 4:10:00 PM
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I'm not sure I agree with the logic of your approach. Wouldn't it be better to build the CSV file after the user has clicked the 'Export' button? After all, if the user doesn't click the button then the effort of fetching the data and building the file has been wasted. I would create the file when the user chooses to export the data and stream the data back directly from memory. This cuts out the overhead of having to write to the file system.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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Not sure I understand -- the CSV (hopefully) doesn't get created until the user triggers the "onclick" event that triggers my exportClick(DataSet) function -- question is how do I get there?
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Sorry, I misread your code. It still seems unnecessary to fetch the data before the user clicks 'Export' though. IMHO, it would be better to fetch the data and stream it back to the browser only when the user clicks the button. Otherwise you need to persist your dataset between page requests. This adds complexity to your application and may be inefficient if the user never elects to download the file. If you followed my approach, you wouldn't have the EventHandler problem.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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Well, there's a lot more going on in this ASPX -- actually the user has already clicked one button to show the data fetched by the SELECT. The purpose of the "Export" button is to allow the user to download an exported CSV of the data he happens to be looking at in his browser .... but Thanks!
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Listen to pmarfleet. Try to learn something from this experience as there are important concepts at the heart of this thread that you seriously need to understand.
Also delete your post from the C# forum.
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All due respect ... I understand what he is saying and he would be absolutely right -- I'd be crazy to go get the data until I need it. However he doesn't have all the facts of what my entire application already does. The data fetch in question is embedded in a function that gets fired based on a previous postback. This function fetches the data based on what the user has requested, then stuffs an export button (which we are dealing with now) and a printable page button (already sorted and working great) onto the page along with a display of the fetched data ...
It looks basically like this:
http://img143.imageshack.us/img143/5783/screencapmr1.png
Now, please -- can someone help with my question -- I keep reading something about Delegates and Custom Event handlers -- does this ring a bell for anyone?
(Deleted other post, so much for throwing a wide net ...)
modified on Friday, January 11, 2008 5:40:53 PM
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The point I was trying to make previously was that your approach was unnecessarily complicated and probably suboptimal for the task at hand. From your screenshot, it looks like you are working with small, simple sets of tabular data. Is it a major performance issue if the data is fetched from the database again if the user selects 'export'? If you were adamant that the data should only be fetched once, you could look at Data Caching[^]. However you should read the documentation and understand its pros and cons if you are considering using it. I think the data requirements your page has are too temporary to consider caching, but it's your choice.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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Hmmm ... yes the sets of data are typically small and simple -- generally not more than 100 rows of a single table. Lets assume I have the event handling function go get the data again. What would be the best method to have the EventHandler know what to get? I still think I'm stuck cuz it would be silly(and probably wouldn't work anyway) to pass the SQL select string in a query string right? Ugh, I guess I could store the SQL string in a cookie -- but that can't be a security best practice ....
Based on your recommendations I'm playing with some other ideas -- what about storing the dataset in the ViewState?
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Your event handler doesn't need to differ from that already specified for the Click event. Within your event handler method, you just need to call whatever method you have to retrieve the data from the database. Remember, the click event fires in your server-side code, so cookies/query string variables are not relevent.
GusNElmer wrote: what about storing the dataset in the ViewState?
ViewState is another option. One advantage of using ViewState is that the data is stored on the client not the server, so no server-side resources are consumed. Its main disadvantage is that it bloats your web page. DataSets are quite heavy objects. To add a DataSet object to ViewState, it would first have to be serialized and the resulting string base-64 encoded. The size of your web page is going to increase significantly, which means longer download times. Try it out for yourself to see what effect it would have. It is usually recommended that ViewState caching is limited to simple scalar values and caching of more complicated objects performed on the server-side by using the .NET Caching API or Session state.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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Okay, here is the issue I am having:
I have created a web app that puts applicant's information into a database. From there the user can do a search for particular users. There is also a function to create a report based on a series of sql queries. The report is created by calling an existing word document, which is in a .doc format, and then replaces bookmarks in the file with the results of the queries. Once that is done, the vb code will then save the report under a new file name and then have the user either open or save the new file on their computer.
Here is where the problem lies. For the past month when I got this originally working, I was able to put my web app into the IIS on my computer so I could test it out on the internal network without migrating it to it's permanent home. It was all working fine until yesterday, when I rebooted my machine. Now, when I call the code to create the document, my browser's progress bar will stop at about 25% of the way and nothing will happen. I can see that the aspnet worker process is running and has called winword.exe and the sql process, but nothing will happen.
When I go to debug the app, here is the line that it is stopping on:
<br />
Dim doc As Microsoft.Office.Interop.Word.Document = wordApp.Documents.Open(filename, confirmConversions, isreadOnly, addToRecentFiles, _<br />
passwordDoc, passwordTemplate, revert, writepwdoc, writepwTemplate, format, encoding, _<br />
visible, openRepair, docDirection, notEncoding, xmlTransform)<br />
The funny thing is that I can run the code just fine when I go back to my original debug folder on my machine. What am I doing wrong here?
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Hi,
I have a asp.net web application that uses UDL files to connect to the database. I stuck into a very strange situation where application is sometimes using this UDL to make connections to the database and sometime errors out stating "Unable to load the UDL file".
I am sure what is causing this behaviour in the application. But it is apprent that the same piece of code(without modifying anything) works today and error out tomorrow and again start working by itself.
Any help in this regard would be highly appreciated.
Regards.
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Hi,
I need to point to the folder that is outside of the root directory. For example, if my project name is SWB and it is located in SWB folder I need to point to the folder that is outside of SWB folder.
Can I use Server.MapPath for that?
Thanks!
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You could set this folder up in IIS as a virtual directory within your website.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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Thanks for reply,
Is the re any other way to do it without IIS, cause I don't have it.
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What web server are you using to host your ASP.NET application if you're not using IIS?
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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I'm using Web Developer 2005, on Windows XP Media
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asem0525 wrote: I'm using Web Developer 2005, on Windows XP Media
You are confusing a web development tool with a web server. Visual Web Developer 2005 is a web development tool that allows you to create ASP.NET website. When you come to deploy your website to a production environment, you would need to install a web server such as IIS to host your website. IIS would be the obvious choice as it is a Microsoft product and has features specifically designed for running ASP.NET websites.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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well, yes,
it is actually my school project and I don't think I'm gonna upload it to the Internet.
is there a way to point to the folder outside of the root folder on my local computer?
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Unless you use a web server such as IIS to define an external folder as a virtual directory within your own website, I don't think you can do this.
Paul Marfleet
"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush
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I am beginner in ASP.Net and have following question:
I have a class and inside of this class i load some information from database.
It is very slow to connect in each instance of this class to database again.
class DataNode
{
SqlConnection DB;
public DataNode()
{
DB = new SqlConnection("connection string");
DB.Open();
}
public DataNode[] ProcessAllSubNodes()
{
DataNode subNode = new DataNode();
subNode.GetSomeDataFromDB();
}
}
I have tried following to avoid it:
1) make SqlConnection DB - static.
Problem: if many users connect simultaniosly - i get error that datareader already used somewhere else.
2) to store DB instance in HttpContext.Current.Session and reuse it each time. It has helped, but i am not sure that it is ideal way and has no bad effects.
I know about caching objects in HttpContext.Cache, but the first time (when there is no cache) it connects to database so often (because my objects are recursive), that database stops responding and i get DB connection timeout exception 
So if someone knows a good pattern for my problem, please share 
Thanks.
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The rule of thumb for database access is to open the connection as late as possible and close it as soon as possible. The slowness may simply be caused by the connection to your database, say if it is located on another server.
If the data is static, i.e. doesn't change often, then caching it may be an option, depending on the amount of data.
There are an enormous amount of examples of constructing data access layers, I would suggest you try searching for one as an example.
only two letters away from being an asset
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I have been trying to send an email from ASP.NET 2.0 application.
It worked fine when i executed the code in the localhost. I was able to send mails through the email server and also received the same.
But when i deployed the same code in ftp server I am unable to send the email.
Exception I received is:
"Failure sending mail.System.Net.WebException: Unable to connect to the remote server".
Can anyone help me out in dis.
Regards
Ramya
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I believe the exception is self-explanatory. Check if the deployed server can actually reach the mail server you are trying to use.
only two letters away from being an asset
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Hi Mark,
I understand ur point. But there are two things that has to be noted here.
1. I am able to send email from an asp page inside the same ftp server to mail server that i mentioned earlier, which means that ftp server and mail server are accessible.
2. I am able to access the mail server from my aspx page in localhost , which means that mail server is accessible from aspx page too.
I dont know where exactly the problem is.
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