In asp.net 2.0 I have several "dropdowns" defined using generics (examples eye color, hair color, etc). The fields are all typical; id, text, etc. All are defined as their own classes which must implement an interface I created called ILookup. However, when I try to return a List<> of this class using:[code]
View 2 RepliesI copied the following code from a book that helps to create a serviced component is a solution called SyncDemo in VS2005 with an application project called ClienteSyncDemo and with other class library project The code of the form ClienteSyncDemo is the following Public Class Ejecutar Private Sub btnEjecutar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEjecutar.Click
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I've spent quite a bit of time reading up on generics, covariance, etc., and I am failing to understand why I get the aforementioned compiler error in this type of codeLet's say I have a base "Bill" class made up of a collection of Lines..
Public Class Bill(Of L As Line)
Private _lines As List(Of L)
Public Property Lines() As List(Of L)
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I have the following C# code. Here the validations are kept outside the class to satisfy Open - Closed Principle. This is working fine. But the challenge is - the validations are not generic. It is specific to employee class (E.g DateOfBirthRuleForEmployee). How do I make the validations generic for all objects (DateOfBirthRuleForAnyObject).
Note: Make Generic <==> Make Type-Independent
Note: I have NameLengthRuleForEmployee validation also. New validation may come in future.
class Program
{
static void Main(string[] args)
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Asc() function returns incorrect result?
Dim TestChar = Chr(128) Dim CharInt = Asc(TestChar) ' this is a mistake on Windows 7 x64. Asc(TestChar) returns 136 instead of 128
I executed this code on another computer and the result was 128.
I know there are tools available to rectify this, but somehow i cannot make out the mistake(s) that disallowed the retrieval of records, despite 2 hours of trying and referencing.
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I have designed a complaints form for my work (free of charge just for my cv). I designed the form for the resolution 1280 x 1024. My problem is when a user with a smaller resolution say 800 x 600 uses it. The form will be out of sync with the screen as shown below (tested on my on computer). So I am wondering is there a way to test the screen size of the users computer then readjust the size of my controls according to the size of the screen. By the way all of my controls are anchored so that they stay in the same place.
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i am doing a vb.net windows application. in that i am creating one folder and making it shared and also assigning shared permission to SYSTEM. My code is as given below.
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I need to create a login page as part of an assignment. Problem is, I don't have access and I'm not sure which other programs can be used as alternatives. I am hoping that it's possible to create the login screen using only a If...Then...Else Statement. If it is possible, I'm probably going about it the wrong way, as it skips the first two conditions and goes straight to the 'Else'.
Private Sub OK_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK_btn.Click
Dim Message As String
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I was wondering if there is a way of making a picture have the properties of a checkbox. I want to have clickable stars that change color (from white to yellow) everytime the user clicks on them to represent the rating they put on certain foods.
View 5 Repliesi am trying to write a code in which i need to perform a update but on primary keys how do i achieve it
i have written the following code: kindly look at it let me know where m wrong
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i am trying to write a code in which i need to perform a update but on primary keys how do i achieve iti have written the following code:
Protected Sub rgKMSLoc_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles rgKMSLoc.UpdateCommand
Try
KAYAReqConn.Open()
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I'm developing an app in VB.Net (Visual Studio Express 2008, on Windows Vista) that connects to an Access relational database. The database has 3 related tables (TextSections, LineItems, Cycles) that I'm loading into my dataset. I've set up two foreign key constraints and want all changes to cascade through the related records in the child tables. I cannot get the cascades to reflect through.
For example, when I delete the parent record, the children records remain (in the database - they are removed from the dataset). Also, when I modify the parent record (change the Description field for example), the change is not reflected in the dataset datatable that holds the children records - unless I go through and ReLoad all of the data from the database and re-Set the constraints. I have set the .AcceptChanges, .UpdateRule, and .DeleteRule to cascade, and have also set EnforceConstraints on the dataset. Why aren't the changes cascading through the children?
Below I've pasted (1) the Load Routines for my datatables TextSections (parent), LineItems (child), and Cycles (child of LineItems); (2) the method that creates the constraints in the dataset, and (3) The Save routine for TextSections.
Friend Sub LoadTSTable()
Dim key(1) As DataColumn
Dim newCol As New DataColumn
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I'm experiencing some weird behavior when trying to modify some DataTable objects. Upon the second call to the subroutine, I get the following error when I to copy the source DataTable to a working set:
System.Data.ConstraintException was
caught Message="Column 'pk' is
constrained to be unique. Value
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I have a problem running a simple query: "select distinct payee from table". This query is set up in the dataset and is called GetAllPayee.My code goes something like:
Dim dtSources as new Datatable
dtSources =
Me.TblExpenseRecordsTableAdapter.GetAllPayee
Upon running I get the error:Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.The problem is, I haven't set ANY constraints on either the new datatable, or the dataset table (tblExpenseRecords). i.e. there is no primary key etc.
Can someone please help me out with this problem?I have no problems running the query through the wizard where I can view the results successfully.
i just want to know if there is a way to implement constraint for parameters with a repeating pattern. For that i meant something like this
ParamArray pattern as Integer()
if i need an integer, and any amount of the "pattern" (the pattern here is one integer). so basically the pattern accepts 1 integer and multiples of 1 integer, meaning 2 integers, 3 integers so is there a way to upgrade this so we can have this pattern:
Integer, Boolean
and any valid combinations for this pattern will include
Integer, Boolean, Integer, Boolean
Integer, Boolean, Integer, Boolean, Integer, Boolean
etc, etc
currently the only way i can think of is to wrap Integer and Boolean as 1 object and apply pattern 1, but i was searching for a better alternative?
I just watched a video from Beth Messi about setting up a primary key and foreign key on a table.
I created two tables, one called customer and the other one called orders CustomerID is the primary key to the customer table OrderID is the primary ket to the orders table and CustomerID is foreign key to the orders table
Beth Messi said that this would maintain the integrity of the tables and she also mentioned something about setting up a cascade delete so that when we delete a record in the customer table, the customer's order in order table will get deleted as well.
how I can set up the cascade delete, Meanwhile, I tried deleting a customer record in customer table - a customer with orders, and I got the following error when I clicked save.
The DELETE statement conflicted with the REFERENCE constraint "FK_Orders_Customer". The conflict occurred in database "C:DOCUMENTS AND SETTINGSLOUISLOCAL SETTINGSAPPLICATION DATATEMPORARY PROJECTSWBINDEBUGTEST.MDF", table "dbo.Orders", column 'CustomerID'. The statement has been terminated.
Shall I use try catch to warn the user that the record that I tried to delete has an order? They can't delete the customer unless the orders table's record is deleted first?
I'm building an app that does calculations (in dollar amounts). I want to buildin a constraint that says the value entered into text box must be greater than 0. If the user does not follow this rule, I want them to get an error message.I have the calculations built and the error message, but not the constraint statement i.e. if users enter negative numbers the ouput is negative, which in the context of this app makes no sense. how a statement that would require the value entered into a text box to greater than a value.
View 3 RepliesIm getting a constraint error when running the following code. there are four fields set as the primary key on the table: bid number, phase number, phase version, detail number.
It errors out saying that bidno, phaseno, phaseversion are the keys and unique. it does not mention the detail number, but it will error out as soon as i run the line dtDest = dsbid.phasedetail.copy....or, if i use the clone (as in the example below), it errors as soon as i add the row.
CODE:
I have a datagridview in which the user can add new rows. The datasource is a datatable who has a unique-constraint for the column "Position". Thus, if the user enters a position already existing, an exception is thrown. To avoid the ugly standard error message, I simply handle the dataerror-event and set e.cancel = true. This works. But if the user presses escape, the row_validated-event is triggered. I use this event to format the rows containing new data by changing the font color to red. Here another exception is thrown (SystemOutOfRange-Exception) telling me that the index xxx has no value. How can I achieve row-formatting for new/modified entries without getting this error?
Here is my code:
''' <summary>
''' Catch exception and cancel illegal action.
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
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I have an application that works with a database that uses foreign key constraints.
For example, we have an inventory table that has a foreign key constraint that references a table called case_names. If a user attempts to delete a case name that has any inventory items referencing it's ID, the action is restricted.
How can I display a message to the user that they will understand? 'You can not delete this case as it still contains inventory items.'
My thought is a try-catch (catching different error types?) but I do not really want to use this for something that may be expected.
The application is in VB.Net using MySQL.data
myCommand = New SqlCommand(
"INSERT INTO tblBook(BookCode, BookTitle, Author, PublishingYear,
Price, EnterDate, CatID, RackID, Amount)
VALUES('" & txtBookCode.Text & "','" &
txtTitle.Text & "','" &
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The INSERT statement conflicted with the FOREING KEY constraint "FK_tblBook_tblCategory". The conflict occurred in database "CIEDC", table "dbo.tblCategory", column 'CatID'. The statement has been terminated.
Was that because of my database's relationships?
i'm using a strongly-typed dataset and i created a table adapter with a query and i previewed the data and it works fine but when i run the application it can't fill the table with this query and it throws an exception that it violates a constraint orkeyFailed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
System.Data.ConstraintException was unhandled
Message=Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
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I am new to VB.net and have created a simple master detail windows form. I created a two table data set and then dropped the master table on the form as a continues form or a detail form with several text boxes to enter data. The child form is a data grid and was simple drag and drop from the data-set. All of this was done with drag and drop and I have added nor changed any code.test data that I have added directly to the database shows up with the proper parent child relationships on the form. I can also enter new records into the database using the parent only portion of my form. I can also update a child record.When I attempt to enter a complete record with data in both the parent form and the child data grid I get this error.
The INSERT statement conflicted with the FOREIGN KEY constraint FK_tblComplainant_tblUseOfForce. The conflict occurred in database "C:\SQLFILES\CCTS_2.MDF", table "dbo.tblUseOfForce", column 'UOFID'. The statement has
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I was creating an XML Schema from a project 2003 XML. All was fine until I rebooted the machine and tried to re-open the file. I am now getting an error along the lines of:
"Identity Constraint not declared".
I've compressed and attached the file.
I have a problem that adding a new ROW with duplicate UNIQUE id throws CONSTRAINTException that I cannot always catch.. Randomly general exception halts my VB software, sometimes catching works. here is my code.
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im using try catch to handle this error uponm deletion of record that is foreign key to other table but it seems that my try catch is not working. im using asp.net (VB). can anyone help me???' i want to display an error message in my page.
View 1 RepliesIn vb.net, it is possible to design a function which can operate on generic parameters which meet multiple constraints. For example, it is possible to have a function accept as a parameter a class which inherits from Control and implements IList. This function could use "Control" or "IList" methods on such an object, and also pass the object to anything that expected a Control or an IList [note that this particular combination was chosen to facilitate a brief example, not to be a particularly useful combination].
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This approach provides compile-time type-safety; there's no need for a cast that could fail at runtime. An alternative approach would be to pass the argument as either a Control or an IList, and have the function cast to the other. That would, however, fail at runtime if the object that was passed didn't in fact meet both constraints.
Under what circumstances is it good to use a generic function like the above, in what cases would it be better to have objects which are going to meet both constraints have a new interface like IListableControl(Of T) which would include a TheControl property that would return itself (cast as a control), and in what cases would it be better to have a generic ISelf(of T) interface, any implementor of which would be expected to provide a "Self" property that would return itself as a T?
Using multi-constrained generics, it's possible to do a lot of things without requiring any run-time typecasts, but I don't know what the performance costs are likely to be. I tried writing a short program to generate 65,536 different generic types at run-time, e.g. Foo(of Bar(Of Foo(Of Foo(Of Bar(Of Foo(...(Of Blah)) and it got pretty slow, so I can tell that the time required to handle generics isn't fixed, but I don't know what factors affect it.
I've got this Function:
Public Class QueryStringUtil
Public Shared Function GetQueryStringValue(Of T As Structure)(ByVal queryStringVariable As String) As T
Dim queryStringObject As Nullable(Of T) = Nothing
If queryStringVariable <> Nothing Then
If HttpContext.Current.Request.QueryString(queryStringVariable) IsNot Nothing Then
queryStringObject = CTypeDynamic(Of T)(queryStringVariable)
End If
End If
Return queryStringObject
End Function
End Class
When I try to call it like this:
Dim intTest As Integer = QueryStringUtil.GetQueryStringValue(Of Integer)("stuff")
Dim stringTest As String = QueryStringUtil.GetQueryStringValue(Of String)("stuff")
Dim datetimeTest As DateTime = QueryStringUtil.GetQueryStringValue(Of DateTime)("stuff")
stringTest gives me the error:
'String' does not satisfy the 'Structure' constraint for type parameter 'T'.
I want our other developers to not worry about having to convert a class to a structure or some stuff like that when they call this function. I just want them to be able to put a standard type in the (Of T) and have it work. I don't mind writing in extra calculations to achieve that. The other problem is I also need the function to be able to return an actual null value, so I kind of need the queryStringObject as Nullable(Of T). Which means I have to have T as Structure otherwise it tells me that won't work. So looks like if I change what T is I need to run some calculation to delcare the var as nullable or not.
I tried overloading this method so that one returns T and one returns Nullable(Of T) like so:
Public Shared Function GetQueryStringValue(Of T As Class)(ByVal queryStringVariable As String) As T
Public Shared Function GetQueryStringValue(Of T As Structure)(ByVal queryStringVariable As String) As Nullable(Of T)
And naturally it's telling me it can't do that since they just differ by return types. Is there anyway to overload this? I really don't want to have two functions.
I have the following code that creates a master/detail scenario between a products table and a test table based on the productid: [code]Unhandled exception has occured. the constraint cannot be enabled as not all values have corresponding parent values as you will see, where I add the datarelation between the two datatables i've added a false. This ensures constraints are not created.That solved the problem. However, I want to know if this is the correct solution. It is really difficult to troubleshoot as I cannot reproduce the error. The database is accessed through the network. it could be the network was down at the time so the child records where not inserted hence the error.
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