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Strange Behavior with Generics:
When I define a Generic at class level with a constraint, I get a compile exception , however , when I implement Generic at method level with the same constraint , all goes well ...
Wondering , wether its a bug in generics or the bug lies in my way of interpretation 
Have Tried to explain the problem below :
Case 1:
I have defined a abstract generic class and defined the generic type at class level , with a constraint . Below is the class definition.
public abstract class BaseVOMapper<T> where T:BaseVO
{
public abstract void Insert(BaseVO child , BaseVO parent );
public abstract void SaveChildrens(List<T> childListToPersist, BaseVO parentVO);
}
Below is the implementation o f the derived class , where FlightList is a List<FlightVO> & FlightVO: BaseVO & as per polymorphism ,I assume , I can pass List<FlightVO> where List<BaseVO> is expected.However , I endup getting the below error.
Argument '1': cannot convert from 'System.Collections.Generic.List<ValueObjects.FlightVO>' to 'System.Collections.Generic.List<ValueObjects.BaseVO>'
i.e
public class FlightVO : BaseVO
{
public int FlightId;
public string FlightName;
}
public class ScheduleVOMapper: BaseVOMapper<BaseVO>
{
public override void Insert(ValueObjects.BaseVO child, ValueObjects.BaseVO parent)
{
//((ScheduleVO)child).FlightList
this.SaveChildrens(((ScheduleVO)child).FlightList, parent);
}
public override void SaveChildrens(List<BaseVO> childListToPersist, BaseVO parentVO)
{
foreach (BaseVO child in childListToPersist)
{
ORlayerEngine.Persist(child, parentVO);
}
}
}
------------------------------------------------------------------Code using Generic at Method Level ------------------------------------------------------------------------------------------
Case 2
// generic type specified at method level , with the same constraint
public abstract class BaseVOMapper
{
public abstract void Insert(BaseVO child , BaseVO parent );
public abstract void SaveChildrens<T>(List<T> childListToPersist, BaseVO parentVO) where T:BaseVO ;
}
Below is the implementation of the derived class :
public class ScheduleVOMapper: BaseVOMapper
{
public override void Insert(ValueObjects.BaseVO child, ValueObjects.BaseVO parent)
{
//((ScheduleVO)child).FlightList
this.SaveChildrens(((ScheduleVO)child).FlightList, parent);
}
public override void SaveChildrens<T>(List<T> childListToPersist, BaseVO parentVO)
{
foreach (BaseVO child in childListToPersist)
{
ORlayerEngine.Persist(child, parentVO);
}
}
}
Comparing Case 1 & Case 2 , in case 1 , in the derived class ScheduleVOMapper , the SaveChildrens method has the generic type explicity specified as BaseVO ,
whereas in Case 2 , the method gets the Generic Type at runtime , which anyways as per the constraint has to be of Type BaseVO.
Though , I have my solution implemneted using Case 2 , would really like to get my doubt's cleared
Many Thanks
Girija
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Why do you declare
girijaa wrote: public class ScheduleVOMapper: BaseVOMapper<basevo>
and not FlightVO instead of BaseVO as generic parameter?
I couldn't test it right now, just guessing.
Urs
-^-^-^-^-^-^-^-
no risk no funk
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We’re struggling to register an unsafe assembly on a development server. The message given is:
CREATE ASSEMBLY for assembly 'Pastel.Evolution' failed because assembly 'Pastel.Evolution' is not authorized for PERMISSION_SET
Now I remember running a grant, “USE Master GRANT EXTERNAL ACCESS ASSEMBLY TO [SERVERNAME\User]” on my server, but the target server doesn’t use windows auth, and you can’t grant rights to ‘sa’. Any ideas on how we can allow ourselves to register an unsafe assmemly?
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I need a help about this.
I've made a program to import csv files. Sometimes I caught this error message "must be less than or equal to max (-1)", I've been search at google and I found some messages saying about DataTable.Select(), something about that.
But I don't know why this error happens, if is the number of parameters or lenght of my csv files. The really problem is that error never happens at development time.
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We have a website set up on our local computer for testing purposes and we then roll out the changes to our main server which is remotely accessed. I want to keep the two databases in sync by calling the dataadapter.update method twice passing in the same datatables (I happen to be using a typed dataset) and just changing the connection string for the remote database (I first wipe each database before the update). However, when I try to do this, after the local site database properly updates and I then call the update method again with a new connection string, the update does not work (it doesn't error, it just isn't working properly) and returns an integer value of 0 telling me that no new rows were updated (if I check the database I see nothing was written in.) I am trying to figure out what the issue is. I am guessing it has something do with the row.rowstate on the rows in the datatable telling the update method that these rows have already been written to the database, but if that is the case, is there any easy way to reset the rows so that update can be called again (I tried fooling with the row.setrowmodified but it didn't work and it gave me a concurrency exception)? For now, the workaround I am using is it to create a new dataset before any update is called, go through every row in the first dataset and write them to each table in the new dataset, and then call the update method passing in the tables of the new dataset. This does work, however it slows the program down considerably when building the new dataset. Anyone have any other ideas or suggestions?
modified on Wednesday, April 30, 2008 9:24 AM
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Is it possible to force a TextBox to show it's input cursor even though it's not active?
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Why would you like to do that?
Could you provide the exact requirement?
Regards,
Dave
Dave Traister
Software Engineer
ComponentOne LLC
www.ComponentOne.com
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If I have a Select statement such as-
[ItemCost]*[ItemQuanity] as ItemSubtotal
How do I name the ItemSubtotal column in another select statement so I can-
[ItemSubtotal]-[AmountPaid] as BalanceDue
When I try this it does not know the ItemSubtotal as a valid column name since I created it in a as column name.
Thanks for the help......
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You can't refer to columns by their alias until the ORDER BY clause because they haven't been serialized as the alias until then. So you have to define your two columns as:
SELECT (ItemCost * ItemQuantity) AS ItemSubtotal,
(ItemCost * ItemQuantity) - AmountPaid AS BalanceDue
If you're using SQL 2005, you could write a user defined function, call it subtotal and then use CROSS APPLY like this:
SELECT S.Subtotal AS ItemSubtotal,
S.Subtotal - ItemQuantity AS BalanceDue
FROM OrderDetails
CROSS APPLY dbo.GetSubTotal(ItemCost, ItemQuantity) S
But if your query isn't returning a large number of rows I really wouldn't worry about it and I would use the first method.
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Mark,
Thanks for the help!
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I have created an application using C# 2003
It runs well sometimes, and sometimes it gives the following error
"unable to find a version of the runtime to run this application"
Everytime this message appear, I have to rebuild my application
How to resolve this
Mohammed Gouda
foreach(Minute m in MyLife)
myExperience++;
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And you didn't modify the machine.config file?
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No
Where is that file?
Mohammed Gouda
foreach(Minute m in MyLife)
myExperience++;
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I have a datagrid bound to a table in my database. I want one of the columns, which does not allow for nulls, to be filled with choices that I will supply beforehand. So I set up what was in this case the third column as a combobox and supplied it with my own list of values. Initially when the form loads, the values are displaying correctly (all rows have data in them) and I can select a value from the combobox, however, when I click off the row I keep getting an error saying datanonullallowedexception. All the rows appear to be filled. Is there a way for me to use the values that I am presupplying to be saved in that third field. (I know that a proper db schema would have parent-child tables for the column but for whatever reason I need to do it for the person this way.) The code I am using is simple for the the third column:
Me.DataGridViewTextBoxColumn3.DataSource = productsrows
Me.DataGridViewTextBoxColumn3.DisplayMember = "Product_SKU"
Any help is greatly appreciated.
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Hi All,
My web application is taking too much time to release the page after it loads completly.
Scenario:
I have 9 views in a single page and some views have link with controls in other views. There is no problem with the page load/refresh, afetr it loads the progress bar stays still for some time ie., it doesnt release the page to the user.
Maximum users in the system would be 2600, but as per my perception it doesnt really hurt the application, since it loads quick but takes time to release the page(Struck). Today only 102 users logged into the system at peek time.
Please someone suggest how to tackle this issue.
Im using framework 2.0, SQL Server 2005 and IIS 6 in Windows 2003.
Thanks,
Bala
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Hi everyone.
My customer has a COM object called validatecom.dll. I need to use this in my VS2005/C# web service. So I used tlbimp.exe to create a Runtime Callable Wrapper for validatecom.dll, defining the namespace as "wsl" because that makes sense in their environment. The COM interface is called IValidate, thus giving me a class called CValidateClass.
In my unit test, which runs as an ordinary .NET application, I can instantiate a wsl.CValidateClass object and call methods on it. No problem.
When I try to instantiate wsl.CValidateClass in my Web Service, however, I get an error, to wit:
System.UnauthorizedAccessException: Retrieving the COM class factory for component with CLSID... yadda yadda yadda... failed due to the following error: 80070005.
And as we all know, 80070005 is another way of saying "Access Denied." Now I'm wondering why I can access the RCW assembly from an ordinary application, but not from a Web Service. I tried giving "full control" rights to "everyone" on that RCW assembly, but still no joy.
Any ideas on this? I'd be happy with a pointer to an MSDN article, a Google term, anything!
Thanks to all for your help.
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Well Mike, yes and no.
I've got the Runtime Callable Wrapper, and I can use it (still) from an ordinary console application, but I'm still getting those errors when I try to instantiate the object from within a web service.
I found out that when I just try to load the assembly directly using System.Reflection.Assembly.LoadFile(filename) it fails with the same error. But System.Reflection.Assembly.LoadFrom(filename) appears to work, as does System.Reflection.Assembly.ReflectionOnlyLoadFrom(filename).
When I use System.Security.Permissions.FileIOPermission to determine my ASPNET user's rights on the assembly DLL, it tells me I have full rights, so it's not a matter of file access.
And I pulled apart the reflection data to find that I'm depending only on mscorlib, which can't be the problem either.
I finally tried signing my RCW assembly just in case it was ASPNET not wanting to run unsigned code.
So... it looks my specific question is: what is it about the ASPNET environment that makes loading a RCW assembly (or any assembly?) so different from a console environment? Is there a document that addresses that?
Thanks to all.
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Hi,
I have a problem to make a CAB file for my project exe (create in Visual studio 2005, C#) into PocketPc 2003. When i execute a cab on a PDa with pocketpc 2003 I retrive an error: "It's not a valid CAB file for windows CE".
The CAB work perfectly on PDA with windows mobile 5.0.
Why? I can create a CAB file compatible with pocketpc2003?
Thanks a lot.
Alex
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i wanna know that Application.Run only takes only from objects as a parameter like
Application.Run (new MYfrm1);
OR it can also take parameter other than windows form like Class Objects?
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Double Post - please ignore.
Giorgi Dalakishvili
#region signature
my articles
#endregion
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Hello,
I have this piece of code which i am using in my application developed on VS2003. i have migrated the code to VS2005 and have cleaned the code, but now i have to port it to Vista.
The code uses SHFILEOPSTRUCT and SHFileOperation which are nwo deprecated and a new interface IFileOperation has been introduced for Vista. I did a lot of head banging but still i could not figure out how to modify my code except the use of SetOperationFlag() function of IFileInterface. So please see if you could help.
Here are the snippets
<br />
SHFILEOPSTRUCT shfileop;<br />
<br />
shfileop.hwnd = NULL;<br />
<br />
shfileop.wFunc = FO_DELETE;<br />
<br />
shfileop.pFrom = pstrfrom;<br />
<br />
shfileop.pTo = NULL;<br />
<br />
shfileop.fFlags = FOF_NOCONFIRMATION;<br />
<br />
shfileop.fAnyOperationsAborted = 0;<br />
<br />
shfileop.hNameMappings = 0;<br />
<br />
shfileop.lpszProgressTitle = 0;<br />
<br />
SHFileOperation(&shfileop);
I get the pFrom and pTo from LPCTSTR type strings. I would also like to know about the double null termination of strings.
Thanks and regards,
Mustanseer
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SHFileOperation is deprecated, not removed. Deprecation simply means that they have added a new method which they advise is used in future, and that they might remove the old way in future operating systems. However, IFileOperation is not available before Windows Vista which means that if you need to support older operating systems, SHFileOperation is the best choice.
The double null-termination is because SHFileOperation can work on a queue of items, not just a single item. Each item is a normal null-delimited string, and the queue is represented by all the item strings concatenated together. The end of the list is marked by an empty string, i.e. a single null character. To remove a single item, therefore, you pass the string (null-terminated) followed by another null, so it appears to be double-null-terminated.
Example: you want to delete items Item 1 and Item 2. Therefore you specify the string
Item 1<NUL>Item 2<NUL><NUL> I have to admit, I can't see how you get hold of an IFileOperation pointer. They seem to have forgotten to document that.
DoEvents: Generating unexpected recursion since 1991
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