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I've got a Singleton instance of my class(A) that contains the functions for filling (passed on)datasets using 1 of 2 resident data adapters: the default adapater(A1) (for executing queries that will not be updated back to the database), and one for specially created and monitored for the query(A2) (that can be used to update data back to database). This all operates using delegates and call backs to the calling class'(B-Z) method. The database is hosted on the internet so, i need the delegation so the ui threads are not waiting for the data to return from the server.
What i'm not sure about is how the lock() will affect my program flow and what will happen when i lock the singleton instance A. At this stage i'm only locking the A1 adapter instance. I want to lock the whole instance of A so that other data requests don't interfere with the current data request.
Will it lock(A) the lock the instance in use by other classes in other threads or should i rather use a single line queue for data filling/updateing?
I would appreciate if some can enlighen me.
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If you use lock(A), the A object will only be accessible for the thread that locked it. Any other thread that wants to access the object will wait until it gets unlocked.
There are different cursor types that decides what happens to a database result when data in tables changes. If you use a static cursor (adOpenStatic), the result is a static copy from the table, and won't be affected by changes in the table. If you can make the adapter use a static cursor, you don't have to use locking to protect the data in the result.
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b { font-weight: normal; }
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Guffa wrote: make the adapter use a static cursor, you don't have to use locking to protect the data in the result.
the reason is not for data protection - its to minimize adapter creation and optimize adapter use during runtime.
Guffa wrote: Any other thread that wants to access the object will wait until it gets unlocked.
does this happen 'automaticlly' or should it controlled by the .NET Monitor class?
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A correction to my previous statement:
The lock statement doesn't lock the object per se, it only prevents the code in the lock statement (or any other lock statement using the same object) to be entered by another thread.
The object is only used as an identifier, so it doesn't matter what object you use if you only have one lock statement.
The lock statement calls System.Threading.Enter, which uses the Monitor class. A lock statement is the convenient form of:
try {
System.Threading.Ender(theObject);
... lotsa code
} finally {
System.Threading.Exit(theObject);
}
---
b { font-weight: normal; }
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What is your question?
"On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question."
--Charles Babbage (1791-1871)
My: Website | Blog
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Yes
Regards,
mav
--
Black holes are the places where god divided by 0...
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Hi all
I am in urgent need of help from you people.
In my web page the user has to insert date several times.so i thought of creating user control.I did that and it worked nicely. but the problem in that is the calendar is opening in the page.So i want to create a window for displaying the calendar and returning the date in the textbox with only c# code i.e. No javascript.
Kindly send the solution as early as possible. I want to repeat once more that i don't want javascript code to create the window only C# code is needed.
Thanks in advance
nauty
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I think you can use the query string instead. just create a new web form and keep the calendar control on it. then when user want to select a date open that new web form. Here the user will select the date and click ok button the calendar control web form.
In the code behind for the ok button redirect the page to its origin with the selected date as query string. This link would be built when the web form is loaded from the source page, again through query string.
For this solution you will have to modify the code for the source page to accept date as a query string to the page. When you get a date through query string you can easily set it to a text box control.
there is some extra coding in this way but it is a simple solution for your problem. Reply me if you have some confusion.
Anant Y. Kulkarni
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Good approach 
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Hi Anant
The approach is really cool.but i don't kno how new window is being made in c#(without javascript) and how to close it after redirecting it back to the parent page.
could you send me some sample code.
If you've the code for the same using javascript please send me.
Thanks for the help.
my id is ashishnautiyal@hotmail.com
nauty
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Hi,
First of all you create a new web form for your calendar control. That means this new web form will contain only the calendar control and the ok button. Now you modify the source web form to accept a query string named, for example date like this --
private void Page_Load(object sender, System.EventArgs e)<br />
{<br />
try<br />
{<br />
string dt = Request.QueryString[0].ToString();<br />
txrDate.Text = dt;<br />
}<br />
catch<br />
{<br />
}<br />
}<br />
You can check for post backs according to your program logic.
The code for button which will display the calendar web form will go like this --
private void cmdDate_Click(object sender, System.EventArgs e)<br />
{<br />
Response.Redirect("calendar.aspx?url=webform1.aspx");<br />
}
i have assumed that the calendar control is placed on calendar.aspx and the source web form is webform1.aspx
now its turn of the calendar.aspx web form
write following code in page load event
private void Page_Load(object sender, System.EventArgs e)<br />
{<br />
try<br />
{<br />
url = Request.QueryString[0];<br />
}<br />
catch<br />
{<br />
}<br />
}
here i have used a string variable named url to store the source url which will be sent to calendar.aspx through query string.
now for the ok button on calendar.aspx write this code --
private void cmdOk_Click(object sender, System.EventArgs e)<br />
{<br />
if(url != "") <br />
{<br />
Response.Redirect(url + "?date=" + Calendar1.SelectedDate.ToShortDateString());<br />
this.Visible=false;<br />
}<br />
<br />
}<br />
here my calendar control name is calendar1
this.visible=false will hide the calendar.aspx page. similarly if you want you can hide and show the source page. But be sure to check the visible property where it is to be set to true where to false.
hope you have understood the code. Its just simple.
Anant Y. Kulkarni
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What you are describing is not possible without Javascript.
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why not javascript???Ok use cookies or cross-page posting
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hello..
i'm thinking of learning to use c++..i just know a little about developing codes..
right now i'm doing something about string..
i'd like to know a way to break a string input to char..i'm quite new to the programming vocabulary so i hope u all know what i mean..
plss help me..
fe8her
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This is quite simple in c#.
just instantiate a new string variable and call the ToCharArray() method on it. This method returns a char[] which you can use for your purpose. I will show you an example-
string temp = "sample string";
char[] temp_array = temp.ToCharArray();
now using various loop statements you can do some processing on the temp_array.
Anant Y. Kulkarni
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You can access characters in a string as if the string was an array of char:
string s = "Orange";<br />
char c = s[2];
You can't modify characters in a string, though, as strings are immutable. For that you would have to create an array using ToCharArray.
---
b { font-weight: normal; }
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Hi,
I am trying to send mails from my c# windows application. For this i have added reference to the web namespace and am using the SmtpMail class. But when i run the application it gives me an error that Cannot contact the Smtp Server or sometimes it gives an error that the Smtp server not found.
I think my Smtp server may not be configured properly to send mails. Can any body provide guidance on this issue.
My code goes like this -
SmtpMail.SmtpServer = <my pc name>
SmtpMail.Send(from, mailto, subject, body)
The arguments will be taken from text controls on the form and passed in to the variables "from","mailto",etc...
I hope somebody suggests me the solution. I am sure that the code must be working, but the smtp server might be not configured properly.
Anant Y. Kulkarni
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I assume your local SMTP server is not running properly, or it is not configured to wait on the default port. What kind of mail server to you have installed?
If you cannot find the server's manual, try the public SMTP server which you also use with your mailer application (copy the name from your outlook/thunderbird settings).
_________________________________
Please inform me about my English mistakes, as I'm still trying to learn your language!
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hey...
try This..
MailMessage ObjMail = new MailMessage();
ObjMail.Subject = Subject;
ObjMail.From = From;
ObjMail.To = To;
ObjMail.Body = MailContent;
ObjMail.BodyFormat = MailFormat.Html;
SmtpMail.Send(ObjMail);
here Subject,From,To and MailContent all are variables..and u have to specify their values..try with this surly the mail will work
Cheers!!
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thanks for the code but i used the same code and it gave me the following error. If you know something abt it please reply me.
Could not create 'CDO.Message' object.
Anant Y. Kulkarni
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Hi,
may I ask related to this post, how can one save a MailMessage to a file pls? Thanks.
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if you want to save a mail message you can use serialization. just serialize the mail message object to a file and next time deserialize the object to display its contents.
Anant Y. Kulkarni
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Hi,thanks for your reply. I think that a MailMessage object can't be serialized. I'm doing:
Stream s = File.Open("C:\\tempemails\\hello.eml",FileMode.Create);
BinaryFormatter b = new BinaryFormatter();
b.Serialize(s,mailMsg);
s.Close();
where mailMsg is the MailMessage object. Am I doing something wrong or it's because MailMessage object's can't be serailized? Thanks.
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There is discussion on this same topic of serializing mail message class at http://www.csharp-station.com/ShowPost.aspx?PostID=11362[^].Please read it. I think it is too complex.
Otherwise you can manually save a MailMessage object by creating your own format. write a method to read all the necessary properties (you think) must be saved and write it to a file. Next time when you want that saved message just create a temporary mail message object and assign property values from the file. If you want security then just encrypt while you save the object and, ofcourse, decrypt before assigning the properties.
Anant Y. Kulkarni
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