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Hi,
Sorry, this is the error message:
System.NullReferenceException: Object reference not set to an instance of an object.
Thanks,
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As I said you should initialize your label . It may deleteted in your InitializeComponent() method.
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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Thanks for your help!
May I ask how I may initialize the label?
Thanks again...
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Something like this:
Label mylable = new Label();
this.Controls.Add(mylabel);
If you use VS.NET when you drag and drop controls in your ASPX file it do all the code for you , but if you don't use it or create your class without it, just create simple web project project , add a label in your webform. Then go to your aspx.cs file and find InitializeComponet() method , all you need is there and you copy/paste same things. The controls and their properties/events are all register their and add to the control.
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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If the Label is declared in the .aspx file, you don't instantiate it in your code-behind file. The page instantiates it when compiled. Since the code-behind must declare it as protected, this field gets set by the child class (the .aspx page).
Microsoft MVP, Visual C#
My Articles
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Oh, yah. I mixed up with windows application. 
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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It just occured to me that your using 'this' in front of everything. You don't need to...
RageInTheMachine9532
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Dave Kreskowiak wrote:
It just occured to me that your using 'this' in front of everything. You don't need to...
It doesn't change anything. It refer to Page class and controls are added to it, you can use if you want.
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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Mazdak wrote:
you can use if you want.
That's what I mean...it's just a bunch of extra typing for nothing...
RageInTheMachine9532
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This is a very inflexible solution. Why not just use forms authentication? It's really easy to use. You simply put an authentication[^] section in your application's root Web.config file. You can add the credentials - even using plain-text passwords - right there in the file and forego having to implement a database or other data source for credentials. Then add an authorization[^] section for each location (either in your root's Web.config or in sub-directories' Web.config files) for directories you want to protect.
Then just read about the FormsAuthentication[^] class for a simple example of a page to gather credentials and the code to create the authentication token, which is an encrypted token (read: secure - much more than sessions).
This gives you the flexibility to support different data sources for credentials. And even if one day you change the username and/or password, with your approach you'd have to recompile for something so trivial. Even which putting this in the Web.config file you can change it easily without having to do anything else (the change would case the web application to restart but that's transparent).
If you want to add role-based authorization, see my article, Role-Based Security with Forms Authentication[^].
Microsoft MVP, Visual C#
My Articles
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I'm creating a data-driven Windows Form dialog which has two combo boxes both of which are lookups to the same table: one is HomeNationID, the other CurrentNationID looking up the Nation (NationID, Description) table.
I have set both combos to have their DataSource as my Nation table with DisplayMember as Nation.Description and ValueMember as Nation.NationID.
When I Show the form I get a runtime error Error creating window handle. (an OutOfMemoryException), it's InnerException is Object reference not set to an instance of an object., the stack trace goes back through ComboBox.SetItemsCore, ListControl.DataManager_ItemChanged and Forms.Control.UpdateBindings (with some others in between).
I can't add the Nation table a second time to the DataSet (not allowed two tables with the same name).
This doesn't seem like a particularly odd requirement - two combos with the same lookup table.
PeteB
I wouldn't say "he's not the sharpest knife",
I'd say "he's a spoon."
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Only use "Description" and "NationID" as the DataMember value, not "Nation." prepended to them. See the documentation and the example for the ListControl.DataSource property (which ComboBox inherits) foro more information.
Also, if you want to better understand why, read about the CurrencyManager.
You can have two combos with the same lookup table, though. One problem you might have that I've seen a few times is that since binding is a two-way deal, changing the value of one combobox will change the other. If this happens, simply use DataTable.Clone to get another DataTable to bind to.
Microsoft MVP, Visual C#
My Articles
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Actually, the combo boxes work perfectly on their own, there is only a problem if they both link to the same lookup DataTable. The problem is that of sharing the DataTable. I was hoping that there was a more elegant solution than cloning the DataTable but if that's the only way...
Thanks
PeteB
I wouldn't say "he's not the sharpest knife",
I'd say "he's a spoon."
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Pete Burgess wrote:
...there is only a problem if they both link to the same lookup DataTable.
That's what I was describing, which is why I said you have to clone the DataTable.
Microsoft MVP, Visual C#
My Articles
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How can I get the name of the user who started the app?
Thanks.
Nilson
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Environment.UserName
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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Thank you very much.
Nilson
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Hi all.
I am designing a C# project which has so much to do with databases. Up to now , I didn't have much experience about multiuser apps.
Which database (Access , SQLServer, NOT Oracle ....) should I use for a "multiuser & high-frequency accessed & middle mass" data record?
Any proverb or url is welcome. (A comparison schema you know?)
Utku KAYA
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Access is not for multiuser usage, its a desktop database. You should use SQLServer .(Of course I didn't talk about price & licening)
Mazy
"Man is different from animals in that he speculates, a high risk activity." - Edward Hoagland
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Access can be used for workgroups, but it isn't optimized for such and can be much slower since it is file-based.
Microsoft MVP, Visual C#
My Articles
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SQL Server has specialized support in the .NET Framework and has since 1.0. Oracle does not as well starting with 1.1 (there was a separate install before, but it wasn't officially supported).
Price is definitely a concern with both. Like Mazdak said, though - Access is not optimized for multi-user environments. It's also file-based, and any file-based database solution has major cons.
One nice thing about SQL Server, though, is that they have a freely downloadable and distributable desktop engine called MSDE. For all intents and purposes, it is SQL Server. It doesn't support near as many connections (only 10) but supports everything else from transations to backups.
You can find more information about it at http://www.microsoft.com/sql/msde[^]. If you installed the defaults for VS.NET, you'll also have the setup on your machine already in the Setup\MSDE directory of your VS.NET installation root. Having applications like VS.NET, FoxPro (last I checked many years ago), Access, Office, and few others gives you redistributable rights to MSDE. Check it out.
The really nice thing is that if you ever need to upgrade to the full SQL Server solution, just re-use the same MDF and LDF files from MSDE. Like I said, for all intents and purposes MSDE and SQL Server are the same.
Microsoft MVP, Visual C#
My Articles
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iam developing application that get binary data from the database(.doc)files and iam storing these file in local files while dealling with it and after i finish i call
System.IO.File.Delete(myfile);
but most of the time the file doesn't delete
so if any one know granteed way to delete my temp files
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Files cannot be deleted while they're kept open.
Are you sure that you close all stream which accessed the file, before trying to delete it?
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i do not make streams with these files
these files r doc files and i have activex control on my form opens these files
and when the user exits the application these files must be deleted.
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Then your ActiveX controls MUST close the files before the app exists. There must be some way of telling the ActiveX control to close it's files. If not, you're going to have to come up with some kind of shell around your entire app that waits for your app to close, then deletes the files...
RageInTheMachine9532
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