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Hello,
I am having trouble updating to a database using a dataset. My code is listed below with the error description. I hope you can help me.
cnnTeacher.Open();<br />
<br />
dsTeacher.Clear();
DataRow drUpdateTeacher;<br />
<br />
daTeacher = new OleDbDataAdapter("SELECT * FROM Teacher",cnnTeacher);<br />
OleDbCommandBuilder cbTeacher = new OleDbCommandBuilder(daTeacher);<br />
daTeacher.FillSchema(dsTeacher, SchemaType.Source, "Teacher");<br />
<br />
drUpdateTeacher = dsTeacher.Tables["Teacher"].Rows.Find(txtTeacherID.Text);
drUpdateTeacher["TeacherID"] = txtTeacherID.Text;
drUpdateTeacher["FirstName"] = txtFirstName.Text;<br />
drUpdateTeacher["LastName"] = txtLastName.Text;<br />
drUpdateTeacher["Email"] = txtEmail.Text;<br />
<br />
daTeacher.Update(dsTeacher,"Teacher");
Error description - SystemNullReferenceException: Object reference not set to a instance of an object
Many thanks in advance,
Steve
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Hello,
I think it is because you don't initialize your drUpdateTeacher object.
Try to do :
daTeacher.FillSchema(dsTeacher, SchemaType.Source, "Teacher");
//Code to add
drUpdateTeacher = dsTeacher.Tables["Teacher"].NewRow();
drUpdateTeacher = dsTeacher.Tables["Teacher"].Rows.Find(txtTeacherID.Text);//Find the row to update
This would be my first guess.
Anyways, most of the time, this error message indicates that you did not initialize an object before you used it.
Hope this helps
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Hello,
Thanks for yourr reply.
But won't the NewRow() add a new record to the table. I was trying to update an existing row not add a new one to the table.
Many thanks in advance,
Steve
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Hello,
No, the NewRow() function does not add a line to the existing table, it creates a line from the row without adding it to the table (it creates the column as they are in the table)
The function DataTable.ImportRow(DataRow row) is the one that adds the line.
You have to create the row with the NewRow function because otherwise, the compiler won't be able to know how many columns there is in the table, what are the columns name/index, etc.
When you create your DataRow object, it has a null value until you write the
row = DataTable.NewRow() statement.
Hope this helps!
Hugo Migneron
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Hello,
I want to add a Splash Screen to my Smart Device Application. The situation is as follows:
The Form1.cs is my Login Page, the Splash.cs is my Form which should displayed about 3 seconds and then should automatically go on to the MainMenu Form.
To reach that I made the following:
In the Form1.cs exists a button which forwards to the MainMenu with these two lines:
MainMenu mainMenu = new MainMenu();
mainMenu.Show();
In the Constructor of the MainMenu Form I wrote after the InitializeComponent() the following lines:
Splash splash = new Splash();
splash.Show();
And in the Splash.cs I import the following method:
[DllImport("coredll.dll", CharSet=CharSet.Unicode)]
public static extern void Sleep (int dwMilliseconds);
public const int IDC_WAIT = 32514;
public const int IDC_ARROW = 32512;
public const int IDC_IBEAM = 32513;
public const int IDC_CROSS = 32515;
public const int IDC_UPARROW = 32516;
public const int IDC_NO = 32648;
public const int IDC_HELP = 32651;
private System.Windows.Forms.Label label1;
public const int IDC_HAND = 32649;
and in the Splash_Load method I wrote the following:
Sleep(3000);
this.Close();
Unfortunately this does not work correctly. Does anybody know what went wrong??
Best Regards
mat
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Instead of pInvoking Sleep, why not use the Sleep method build into .NET
See MSDN's library reference for Thread.Sleep[^] for details
Do you want to know more?
Vogon Building and Loan advise that your planet is at risk if you do not keep up repayments on any mortgage secured upon it. Please remember that the force of gravity can go up as well as down.
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On top of what Colin said, the Sleep should not go into the Splash screen. Instead, the code should go into your Main form, using something like:
splash.Show();
Sleep(3000);
splash.Close()
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Hi,
I've currently got a program that emulates the command prompt in C#. So my application hooks into cmd.exe and then via a pair of text boxes in my application, I can stream the command prompt input and output back and forth. This works fine on my local machine.
I'm looking to set this up so that there will be 2 applications. On machine A, the application will connect to cmd.exe on machine B. Then from the application on machine A, I can send console commands to machine B's cmd.exe and receive output back.
Does anyone have any recommendations as to how I should go about this?
Any help is much appreciated
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could anyone helpme out....i want to make a windows application that has phone, fax, answering machine facilites...this can be acheived through TAPI provided u have a TAPI compliant modem....how do i get strated on this...all the hlp on MSDN is in C/C++ and i cant make head or tails of it....and....i misgt be a little slow in replying as i am unable to access the internet everyday...
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Do yourself a big favour. TAPI and C# are a bad combination, especially if you've never written any TAPI applications in C++ before.
My strategy when writing TAPI applications in C# was to use COM Interop with my own TAPI COM wrapper. I also built an XML service in C++ that fired the TAPI events via TCP as XML.
Until Microsoft come out with a better approach to managed TAPI, you are better off writing your TAPI code in C++.
Michael
CP Blog [^]
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Hi~
The wparam and lparam is the pointer of the variable. I would like to pass string to the other window using sendMessage method in C# by P/Invoke. Then, as wparam and lparam is pointer and C# no support pointer. Then how to send the message with string in C# using sendMessage?
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http://pinvoke.net/[^]
I'd give you a reference directly to the page you need, as there is an example of what you want, but the site doesn't allow you to directly go to a page. You have to search or browse for the API you are looking for.
Do you want to know more?
Vogon Building and Loan advise that your planet is at risk if you do not keep up repayments on any mortgage secured upon it. Please remember that the force of gravity can go up as well as down.
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Colin Angus Mackay wrote:
I'd give you a reference directly to the page you need, as there is an example of what you want, but the site doesn't allow you to directly go to a page. You have to search or browse for the API you are looking for.
Not entirely true, here is the link: SendMessage[^]. 
- Nick Parker
My Blog | My Articles
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For the pocket pc,
why, sometime when the program try to show a form by calling the .Show() method, the form was not shown. However, the form title appear in the task list(memory)?
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Hi,
I am using the System.Web.Mail in a C# program to send email and i want to make sure my program will be usable. I would like to know if everyone who has dotnet installed (dotnetfx.exe for example) will be able to use the program.
I think there is an issue with the CDO/CDONT but i am not quite sure what it is. My application must support WinME, Win2000 and WinXP with dotnet installed. If anyone knows more about the System.Web.Mail compatibility, it would be really appreciated 
Thanks
HM
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The documentation for System.Web.Mail.SmtpMail states that only the following platforms are supported: Windows 2000, Windows XP Professional, Windows Server 2003 family.
Indicative code for getting the OS and CLR version numbers is as folows:
using System;<br />
Console.WriteLine("OSVersion: {0}", Environment.OSVersion.ToString());<br />
Console.WriteLine("CLRVersion: {0}", Environment.Version.ToString());
Please see my article
here[^] for more details:
Salil Khedkar [^]
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There is an issue, and you should not use System.Web.Mail. It requires a CDO server to be installed. Current CDO servers include Microsoft Exchange Server (requires NT Server; the Exchange version may require newer NT-based Windows platforms as well), or the Microsoft SMTP Services which, IIRC, started shipping with Win2K server (perhaps professional, but I don't remember off-hand).
Sending SMTP messages is really not hard at all. Just search this site for SMTP using the search box at the top of every page, or even this forum by clicking "Search comments". I personally have posted numerous examples, as well as sample source in an article on this site to resolve MX records for a specified domain (you need to know the SMTP server to send mail to). The SMTP protocol - at least for simply sending messages with no more support than MailMessage would give you - is very simple.
Note that in .NET 2.0 (formerly named "Whidbey") Microsoft will ship as part of the BCL SMTP and MIME support in classes that do not require CDO.
The System.Web.Mail classes - which should be evident by the parent namespace - is meant for use with ASP.NET, which is typically (but not limited to) run on IIS, where you can also install the Microsoft SMTP Services to send or forward mail, as well as queue received mail.
This posting is provided "AS IS" with no warranties, and confers no rights.
Software Design Engineer
Developer Division Sustained Engineering
Microsoft
[My Articles] [My Blog]
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Thank you for your reply,
Actually, i was using a class called smtpEmailer that i took on this site http://www.codeproject.com/csharp/smtpemailer.asp but i have a problem with the attachments, which i need to send.
Everything works fine with the class, but when i send a email with an attachment, the email is sent/received with no problem but i can't see the attachment. It is like the message had no attachment at all, except for the fact that the attachment is there, since an empty body message is 400k big (when i put a 400k attachment). I searched a lot to find a solution for this problem but haven't found yet. This is the commands i send in the socket for a basic email with a text file attachment:
<br />
HELO xxxx.xxxxxx.com<br />
MAIL FROM:<xxxx@xxxxxxxxxx.com> <br />
RCPT TO:<xxxx@xxxxxxx.com><br />
DATA<br />
MIME-Version: 1.0<br />
X-Mailer: SST_OnSite.SmtpEmailer<br />
FROM: xxxxx@xxxxxxxx.com<br />
TO: xxxx@xxxxxxxx.com<br />
REPLY-TO: xxxx@xxxxxxxxxx.com<br />
DATE: Wed, 27 Oct 2004 19:20:34 GMT<br />
SUBJECT: TEST<br />
Content-Type: multipart/mixed; boundary="#SEPARATOR1#"<br />
<br />
<br />
This is a multi-part message in MIME format.<br />
<br />
--#SEPARATOR1#<br />
Content-Type: application/octet-stream; name="a.txt"<br />
Content-Transfer-Encoding: base64<br />
Content-Disposition: attachment; filename="a.txt"<br />
Content-ID: <a><br />
<br />
<br />
--#SEPARATOR1#<br />
Content-Type: multipart/alternative; boundary="#SEPARATOR2#"<br />
<br />
<br />
--#SEPARATOR2#<br />
Content-Type: text/plain; charset=iso-8859-1<br />
<br />
<br />
Your email client does not support MHTML messages<br />
<br />
<br />
--#SEPARATOR2#<br />
Content-Type: text/html; charset=iso-8859-1<br />
Content-Transfer-Encoding: quoted-printable<br />
<br />
<br />
This is the body of the message<br />
--#SEPARATOR2#--<br />
<br />
<br />
--#SEPARATOR1#--<br />
<br />
<br />
.<br />
QUIT
I know the server works fine (i have no problems with attachments when i send them with System.Web.Mail namespace or with Outlook)
Any Help with this would be appreciated
Thanks
Hugo Migneron
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The fact that you're sending a.txt as an "application/octet-stream" may be the problem as your server or the receiving server - especially these days - is probably stripping it off as a potential threat. Extensions with MIME don't matter, but certain things can be inferred as common threads. Sending a .txt file as a binary stream is one obvious one. You should send it as some text/* MIME type using the appropriate charset with the Content-dispostion set to "attachment".
If you're having problems with a particular third-party library like this, you need to contact the author to get it resolved. There are also a lot of other third-party applications out there to handle this. A good - but cheap - commercial library you can get from IP*Works![^]. S/MIME is even supported if you need it.
Writing your own also isn't that hard, especially if you end up using the same template and don't need the extensibility of a library. I've done this in a couple cases. It's quick, simple, and - for something that doesn't change often - cheap!
This posting is provided "AS IS" with no warranties, and confers no rights.
Software Design Engineer
Developer Division Sustained Engineering
Microsoft
[My Articles] [My Blog]
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I understand how to interrogate the mouse position in an event handler, but how do I programmatically force the mouse cursor to a specific x,y position?
Thanks!
Mark
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Assign the wanted screen coordinates as a Point to the static Cursor.Position property.
www.troschuetz.de
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hi,
i'm creating a simple windows form control,this control contains
some panels but during design time this panels are accessible by clicking on them,i want to know what should i do inorder to disable selecting these panels...
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You wrote :
some panels but during design time this panels are accessible by clicking on them,i want to know what should i do inorder to disable selecting these panels...
I am not getting your clear requirement. What got from this is , you are trying to control the accessiblity on design time. Accessibility is only come into picture when you use that perticular form.
If you can give clear picture of your requirement. Then i can able help you out.
Sreejith Nair
[ My Articles ]
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