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i should not swear on this but i think this is how it works.
if you do
bla var=(bla)some_other_var;
you will get an error if "some_other_var" is null
but if you do:
bla var= some_other_var as bla
it will accept null values to , (i think , ive not tested this but i think i saw that somewhere)
//Roger
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What if data cannot be casted to the type ChannelDataStore? What would happen is there would be an error, and you wouldn't be able to trap the error. So the makers of the C# language included this keyword, so that the variable would become null if casting failed, rather than throwing an error.
"Blessed are the peacemakers, for they shall be called sons of God." - Jesus
"You must be the change you wish to see in the world." - Mahatma Gandhi
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As others have mentioned, casting will throw an error if the cast is invalid. The 'as' keyword will never throw an error - it will return 'null' if the cast is invalid.
MyClass myClass;
object otherObject;
myClass = otherObject as MyClass;
is logically equivalent to the following:
MyClass myClass;
object otherObject;
if( otherObject == null || !typeof(MyClass).IsAssignableFrom(otherObject.GetType()) )
myClass = null;
else
myClass = (MyClass)otherObject;
--
Russell Morris
"So, broccoli, mother says you're good for me... but I'm afraid I'm no good for you!" - Stewy
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That's the best explaination i have seen today. Thanks.
norm
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Does anyone know how to list the content of this folder? I've tried using the System.IO.Directory class to no avail.
God, I pity me! - Phoncible P. Bone
If I end up Windows ME someone is going to be hurting. - One of the answers to a question for What OS are you
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Just a gues, maybe you can do it with System.Managgement. There are some classes for Network in WMI.
Mazy
No sig. available now.
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Thanks. I'll take a look at that now.
God, I pity me! - Phoncible P. Bone
If I end up Windows ME someone is going to be hurting. - One of the answers to a question for What OS are you
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Hi,
Im having issues whit a loop.
When i try to return the function in the loop, it tells me the function has no return value.
[WebMethod]<br />
public string GetBiosInfo(string Username, string Password)<br />
{<br />
ConnectionOptions co = new ConnectionOptions();<br />
co.Username = Username;<br />
co.Password = Password;<br />
ManagementScope ms = new System.Management.ManagementScope("\\\\127.0.0.1\\root\\cimv2", co);<br />
<br />
ObjectQuery oq = new ObjectQuery("SELECT * FROM Win32_BIOS WHERE PrimaryBIOS = TRUE"); <br />
ManagementObjectSearcher query = new ManagementObjectSearcher(ms,oq);<br />
ManagementObjectCollection queryCollection = query.Get();<br />
<br />
foreach(ManagementObject mo in queryCollection) <br />
{<br />
return mo["Name"].ToString();<br />
}<br />
}
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What the compiler is saying, is that "not all code paths return a value". This is because you don't return anything outside the foreach loop.
The problem lies in the fact that it is theoritically possible that the queryCollection is empty. If it is empty you bypass the loop and go directly to the end of the method. Return something after the loop and the problem will go away.
Also, are you sure you only want to execute the loop once? I mean right when you enter the foreach for the first time you will be exiting the method also.
-Nathan
---------------------------
Hmmm... what's a signature?
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I have a C# windows appliation with an Access database. There are 2 tables: USERS and PERMISSION_TYPES. Table definitions are:
Table Name: USERS
Fields:
First_Name
Last_Name
Address
PERMISSION_TYPE (FK to PERMISSION_TYPES)
Table Name: PERMISSION_TYPES
Fields:
PERMISSTION_TYPE (PK)
DESCRIPTION
The tables are linked vis the PERMISSION_TYPE field. I can make successful updates to the database, however, I'm trying to use a datagrid for each table so the user can Insert, Update, and Delete records in each table.
When the PERMISSION_TYPES.DESCRIPTION field is changed, an error message is returned that states:
"The record cannot be deleted or changed because table 'USERS' includes releated records"
This doesn't make any sense to me, since the DESCRIPTION field is not a Primary Key, and the updates are successful within Access. I have used the generated Update code, and I have written my own update code - I get the same error message.
Does anyone know what is wrong?
Thanks so much,
Randy
dorianr@mail.com
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Hi Randy,
dorianr wrote:
This doesn't make any sense to me, since the DESCRIPTION field is not a Primary Key, and the updates are successful within Access. I have used the generated Update code, and I have written my own update code - I get the same error message.
This sounds really a bit strange - just as the line would first be deleted, and later inserted again 
I think PERMISSION_TYPES is just a lookup table. Something that helps
the user of your program to sort the records in the user table. Personally I prefer not to have the user edit a lookup table side by side of the main table.
I do this because:
- the permission type is linked to more than one line, editing with only one row is usually specific, and lookups should be general
- On a multi user system not all users should have adminstrator priviledges, eg access to the options. Defining possible permissiontypes (or more general: options)is the admins task
OK, this does not really solve your problem with the table, but perhaps an other way of doing things might be helpful.
Sascha
--
http://www.livingit.de
http://www.mobile-bookmarks.info
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Hi Sascha,
I'm wondering if there is a problem with the datagrid in .NET 2003 (I have experienced other bugs, but that is anther story). The two tables that I'm discussing are both lookup table that are in the Administration module (not all users have access).
I can solve this problem by adding a numeric, primary key to the PERMISSIONS_TYPE lookup table. I have no idea why using a PK for PERMISSION_TYPE would not let an Administrator update the permission type DESCRIPTION. This solution isn't very feasible, since I'm on the last part of a large project - it would set us back by a lot.
Thanks,
Randy
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that and your violating a relationship issues.
I.E.. see FOREIGN KEY RELATIONSHIPS in dbase theory
I'm not an expert yet, but I play one at work. Yeah and here too.
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I'm not violating FOREIGN KEY RELATIONSHIPS, since I can perform this update directly in the relational database. The problem seems to be with using .NET 2003. I've run tests, and I can perform the same update within the database, just not via .NET
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Yes but the error is stating that and key is bound on that column there fore if you destroy that field then you will have an invalid key assigned to other records.
Access is a crap database and thats why you might have gotten away with it, but SQL does a check on those fields.
Its also possible you might be creating relationships with your code but the problem is key relationships defined either in the database table or the dataset table.
nick
I'm not an expert yet, but I play one at work. Yeah and here too.
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Hiya can someone plz give me the code that lists all the network pcs and their ip addresses in c#.
i have been searching the net now for 2 days and it is very hard to find code that actually works.
Thanks a million.
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I use a multi-threading to implement Socket programming...
when a client have connected to server....
Server initiate a new thread to handle this client-Server's communication...
but the problem is....
I use the thread I made to register a Receice_callBack Function(for asynchronization-communicate)，but this thread
stoppd(complete)after doing the register。therefore，the
Receice_callBack can't run correctly(because the thread has stopped....and the error etection happened....
what can i do to make my intantion correctly...???：）
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I'm writing a WebService that outputs a DataSet and need to set a DataRelation for the hierarchical recordset. I've searched and found plenty of parent child table examples, but my table is self referencing by ParentID to RecID. Some ParentIDs are null for top level items. Any ideas?
I already tried cloning the table as below to create the relationship, that bombed...
System.Data.DataTable dtClone = ds.Tables[0].Copy();
dtClone.TableName = "Child";
ds.Tables.Add(dtClone);
string[] strParent = {"RecID"};
string[] strChild = {"ParentID"};
relParChld = new DataRelation("S","Table","Child",strParent,strChild, true);
// Add the relation to the DataSet.
ds.Relations.Add(relParChld);
RecID ParentID
T6975 NULL
T6977 T6975
S34207 T6977
S34209 T6977
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Hi, im looking for an implemantion of some functions, as they are:
Crosscorrelation, Autocorrelation, High-, Low- and Bandpassfilter in C#.
Some help would be nice!
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hi
i ask about6 kan i control windows 98
like disable user from press alt and ctrl and delete
or
from access spicific drive
there is program his name is cybercafepro client
i want to simulate it
the client is controlled by server
i wish that someone can help me
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I was wondering if I made a little app, if I could save the resulting file as an excel file. I searched the articles and found out you can do it through asp .net but I want just a winforms app to do it. What I want to do is either make an app that appends information to an exsisting excel file. Or info on how to make an office addin to take a file and merge it to the currently open file. Any help would be great (heck even some concisive links on information would be nice, not just www.msdn.microsoft.com)
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Well actuall the best tool for this is ExcelWriter by Artisan It does all the encoding and formatting. Of course you can create a plain csv file also but excel writer is awesome for the web and winforms.
This tool is a com and they might have a .net version but I doubt. But it really doesnt matter.
nick
I'm not an expert yet, but I play one at work. Yeah and here too.
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I was looking to make one myself (perferably not asp .net, one to work with winforms) but thanks for the link.
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Well then open an excel file binarily because you have formatting at the beginning.
And really is it worth the development time?
I'm not an expert yet, but I play one at work. Yeah and here too.
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