ADO.NET :: LINQ To SQL Inherited Classes With Abstract Functions?
Aug 16, 2010
I'm building a web app that will keep a events in a database and add the event to a Google calendar on insertion.
I have three types of events, PendingEvents, ApprovedEvents, and DeniedEvents. I'm using single table inheritance through LINQ-to-SQL, with the Event class being abstract and the 3 types inheriting from it
Each type of Event is stored in calendars differently. I would like to use an abstract member function in Event called AddToCalendar.
I'm trying to set this up in a separate class file because I'm using the LINQ-to-SQL designer and I don't want these to be overwritten if I change the LINQ diagram.
However, I get an error from all three inherited classes that "'WebCal.ApprovedEvents' does not implement inherited abstract member 'Edu.Northwestern.WebCal.Event.AddEventToCalendar()' WebCalendarWebApplication1App_CodeWebCalDataSource.designer.cs"
It looks like it won't check my outside file and only looks at the designer.
The non-designer partial class file looks something like this:
public partial class WebCalDataSourceDataContext : System.Data.Linq.DataContext
{
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[Code]....
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[URL]
1. If you anticipate creating multiple versions of your component, create an abstract class. Abstract classes provide a simple and easy way to version your components. By updating the base class, all inheriting classes are automatically updated with the change. Interfaces, on the other hand, cannot be changed once created. If a new version of an interface is required, you must create a whole new interface. { Is there any example for this t ounderstand throughly ?} If you are designing small, concise bits of functionality, use interfaces. If you are designing large functional units, use an abstract class. If you want to provide common, implemented functionality among all implementations of your component, use an abstract class. Abstract classes allow you to partially implement your class, whereas interfaces contain no implementation for any members. { Is there any example for this t ounderstand throughly?
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Mar 31, 2010
I am trying to compile the following code and i am getting the error:
Cannot create instance of abstract class .
m_objExcel = new Excel.Application();
m_objBooks = (Excel.Workbooks)m_objExcel.Workbooks;
m_objBook = (Excel._Workbook)(m_objBooks.Add(m_objOpt));
m_objSheets = (Excel.Sheets)m_objBook.Worksheets;
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object[] objHeaders = {"Order ID", "Amount", "Tax"};
m_objRange = m_objSheet.get_Range("A1", "C1");
m_objRange.Value = objHeaders;
m_objFont = m_objRange.Font;
m_objFont.Bold=true;
// Create an array with 3 columns and 100 rows and add it to
// the worksheet starting at cell A2.
object[,] objData = new Object[100,3];
Random rdm = new Random((int)DateTime.Now.Ticks);
double nOrderAmt, nTax;
for(int r=0;r<100;r++)
{
objData[r,0] = "ORD" + r.ToString("0000");
nOrderAmt = rdm.Next(1000);
objData[r,1] = nOrderAmt.ToString("c");
nTax = nOrderAmt*0.07;
objData[r,2] = nTax.ToString("c");
}
m_objRange = m_objSheet.get_Range("A2", m_objOpt);
m_objRange = m_objRange.get_Resize(100,3);
m_objRange.Value = objData;
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m_objBook.SaveAs(m_strSampleFolder + "Book2.xls", m_objOpt, m_objOpt,
m_objOpt, m_objOpt, m_objOpt, Excel.XlSaveAsAccessMode.xlNoChange,
m_objOpt, m_objOpt, m_objOpt, m_objOpt);
m_objBook.Close(false, m_objOpt, m_objOpt);
m_objExcel.Quit();
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Jul 27, 2010
I just want to know that how can I utilize the concept of Abstract class, virtual class etc. in my shopping cart website. I have read the tutorial out there on internet and I saw some examples too, but those examples are so general that they dosen't fit into real world scenerio like I am searching for a shopping website. Same questions again and again comes to my mind that why to made a class only to give the declaration of methods and property.
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Apr 22, 2010
We all know that, we cannot create the object of Abstract class.
But why it is so?
I mean, can anyone explain it with real time example?
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