Cannot Create The Object Of Abstract Class

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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Jul 22, 2010

Why do we use the reference of abstract class (or base class) to create object of it's sub-class. eg: TextWriter is the abstract class for StreamWriter & StreamWriter.

TextWriter writer = new StreamWriter();

why can't we simply use :

StreamWriter writer = new StreamWriter();

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C# - Cannot Create Instance Of Abstract Class?

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;
m_objSheet = (Excel._Worksheet)(m_objSheets.get_Item(1));
// Create an array for the headers and add it to cells A1:C1.
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;
// Save the Workbook and quit Excel.
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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MVC :: Cannot Create An Instance Of The Abstract Class Or Interface?

Dec 12, 2010

Error 1279 Cannot create an instance of the abstract class or interface 'System.Web.Mvc.FileResult'

[Code]....

I am using MVC 2. The same code works in my onather application. I have no idea about this error.

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BareMessage="Cannot Create An Abstract Class."?

Jun 18, 2010

Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Cannot create an abstract class.

Source Error:

Line 150: <providers>
Line 151: <clear/>
Line 152: <add name="NDMSMembershipProvider"
type="CSW.Web.Security.NDMSMemberProvider"/>
Line 153: </providers>
Line 154: </membership>

Source File: C:DevCSW2srcCSW.Webweb.config Line: 152

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When to use Abstract class and when to use Interface class.

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Recommendations For Abstract Class Vs Interfaces?

Dec 21, 2010

From the following URL i got some doubts about the Recommendations for using Abstract class vs interfaces

[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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Use Of Abstract Class In Shopping Portal?

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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Mar 3, 2010

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The data-access approach that I was using so far is the following(I read in some book and liked it):

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Here's where I'm at:

I cannot use <% if (whatever) { %> some stuff <% } else { %> some other stuff <% } %> because I cannot access the databound item to make the choice based on its type. I cannot use the <%# %> syntax, which lets me use the databound information, because you cannot code logic like if...then...else. I cannot (rather not) call a function and return a string with the code because what I want to render is complex and contains further nested databound controls. Has anyone found an ingenious way of doing if it is this type of object, display these controls, else display these other controls?

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ProductId
ShortTitle
Price
Img

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Google Spreadsheet
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sample rows:
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Blue|49|23
Yellow|55|28

My results are
Yellow Color_Summarized FH 55 28

How do I need to set it up so it keeps all the data loaded instead of just the last instance? Is there a better way then putting in class?

My code:

Code:
Imports Microsoft.VisualBasic
Imports System.Data
Imports System.Collections.Generic
Imports Google.GData.Spreadsheets

[code]....

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[code]....

This doesn't "feel" right, but I wanted to check with SO to get opinions of individuals smarter than me on this. I also tested it out, and it seems that the partial keyword on the OnValidate method is causing problems (understandably so). This doesn't seem possible to fix (but I could very well be wrong).

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[Code]....

In the above case AddNewUser method takes the object of User class. But i'm getting casting error. So how do I convert Json object to the "User" class object?

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