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'


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

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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;
// 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);

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Use Abstract Class And Interface Class?

Jan 29, 2010

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

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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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Why Use Reference Of Abstract Class To Create Object

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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Architecture :: Interface, Abstract Or Inheritance?

Oct 7, 2010

I have a table which houses two entities. StaticProgram and DynamicProgram. There is one column in that table called ProgramType which determines if a program is of Type static or Dynamic. Though these two entities are stored in one table (I am guessing because the primitive fields for Static and Dynamic programs are exactly the same) but from a business point of view these are two VERY different entities.

So, I created two Classes StaticProgram and DynamicProgram. However, I donot want to create two seperate Data Access Classes because it is going to be the exact same code replicated twice. I tried creating a "Program" class as base class and inherited StaticProgram and DynamicProgram classes but down casting is not supported so I can't return a "Program" object from the data access class and cast it to "StaticProgram" class.So, what are my options? Can I create an IProgram interface and have StaticProgram and DynamicProgram implement that interface and have my Data Access class return IProgram?

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Create A Log Everytime When Methods In An Interface Class Are Called

Dec 30, 2010

I want to update a log file(txt) everytime when methods in a an interface class are called? Is there any way to do this other than writing code in every method to create log?

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Web Forms :: Inheritance And Interface/abstract Method To Be Implemented On Muliple Aspx Pages?

Dec 13, 2010

I am working on a reporting project using crystal reports. I am a little new to working on making the project dynamic or reducing down code.

I have many aspx pages which are using the same logic of collecting input from textboxes and inputing to business logic layer.

I was thinking if someone can suggest me inheritance and interface/abstract method to be implemented on muliple aspx pages?

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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"
Line 153: </providers>
Line 154: </membership>

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

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C# - How To Create Instance Of A Class Only Once

Apr 4, 2011

A instance of a class is created in the partial class of an aspx page.Under page_load or button click method I'm trying to set the value to the class. but when each postback takes place new instance is created and I'm losing the previous value.

public partial class DatabaseSelection : System.Web.UI.Page
DBProperties dbpro;
Metadata obmeta;
protected void Page_Load(object sender, EventArgs e)
if (!IsPostBack)
dbpro = new DBProperties();

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How To Create Instance Of A Class Dynamically

May 21, 2010

I wanna do smth like this:


Does anyone have a recommendation how this is archievable? I am trying to pass in the Type to the method and then create an instace of it and then access the properties in it.

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C# - Trying To Create Instance Of Class By Using Reflection

Apr 16, 2010

I am trying to create instance of class by using reflection in web site. Class ClassName is defined and located in App_code folder. Following line returns null, what could be wrong.

Type type = Type.GetType("NameSpace.ClassName", false, true);

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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


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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Architecture :: What Is The Function Of Abstract Class

Oct 24, 2010

what is the function of abstract class, why design pattern need to build BLL and DAL

anyone give an example for my reference as I am getting strat to build my web-based project

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Architecture :: Singleton Pattern And Abstract Class?

Aug 19, 2010

I know what Singleton Pattern means and Abstract class means.What I wanted to know was how would this apply to real world.Could anyone give me any good example or simple explanation.Say I have a simple website, why would I use any of the above if any.Why would it simplify my architechture.

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Architecture :: Use Of Abstract Class Design In Real Time Projects?

Jul 21, 2010

What is the use of abstract class design in real time projects

and how to use abstract clases and interfaces

and inheritense concepts

like big shoping portals or content managment,blogs etc

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Creating An Abstract Class That Will Define All Database Manipulation Methods To Implement

Mar 3, 2010

I am developing a couple of small ASP.NET application and would like to know what pattern. approach do you use in your projects.

My projects involve databases, using Data access and Business logic layers.

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

For DAL layer:

Creating an abstract class that will define all database manipulation methods to implement.
The abstract class will contain a static "Instance" property, that will load (if instance == null) an instance (Activator.CreateInstance) of the needed type (a class that implements it).

Creating a classes that implement this abstract class, the implementation will be according to the databases (SQL, mySQL and etc) in use.

With this I can create different implementation according to database in use.

For BLL layer:

A class that encapsulates all all retrieved fields , and static methods that will call the DAL classes.

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Forms Data Controls :: Binding Repeater To List (of Abstract Class)?

Feb 18, 2010

I am attempting to bind a Repeater (but it could be a GridView or ListView) to a list of objects. The List's type is an abstract type, which has two different classes derived from it, both with different properties. Because they have different properties, I cannot just have one ItemTemplate. If I bind a control to a property of one type of class and the other type doesn't have it, it throws an error.

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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Architecture :: Use A C# Class Or A Interface?

Feb 3, 2011

I have a block of SQL statements that I like to use as a sort of function.

I was thinking that I could make a class and inherit all of the master function, then add the parts that I need for other sections of the program in a sub class.

The problem is, up to this point I've been programming ASP .Net through visual studio, and it's kind of just programming behind controls. I'm not sure where to put the class/function/method/interface, or whatever we call it.

Of course you probably know that visual studio creates a bunch of partial classes when you do an ASP. Net application... so.. to get access to a function like object, across classes.. use an Interface?

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.net - Shorten Syntax When Using Class Interface In C# ?

Jan 23, 2011

I have created a Slider User Control which implements ISlider Interface.I have some methods like SetValue below which should accept both ISlider types and standard Slider control type.Am I'm obliged to use this heavy syntax is there any shortcut?

public void SetValue(Object slider, Double value)
ISlider ISlider;
ISlider = slider as ISlider;
if (ISlider != null)
ISlider.Value = value;
((Slider)slider).Value = value;

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Set View Properties From Another Class / Interface?

Nov 16, 2010

There is a SearchPage which has a properties ErrorMessage, SuccessMessage etc. This is basically a MVP pattern so for each page(view) there is IView that contains definitions for all the properties

I am using decoratoe pattern to set these peoperties dependingon the message type. There is another Interface IBaseMessage which has a method DisplayMessage() and a class BaseMessage which implements the interface. This class has a definition of the view

Interface IbaseMessage
public Iview _view{get; set;}
_view.Warning ="<message>"

Here, I am not able to set the message to the view properties. I am getting the error as "Object reference not set to an instance of the object"

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There Is No Interface Definition Of Rwuser Class?

Mar 5, 2010

I have a Class RWuser(base Class)it has diff methods agent is another class it is inherited the base classit has diff methodsfor the above classes i am writing interface definitions in the constructor of a classthe above in one project and i am creating one more project and add ref of the above to this one when i am calling Child Class(Agent)it giving error like there is no interface definition of rwuser class


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C# - Store Class Instance (helper Class) In Cache?

Jun 30, 2010

I have a class instance which is created by using Activator.CreateInstance() method. That class instance contains helper methods which are frequently used throughout the application. In order to avoid creating the instance multiple times, I'm just thinking about implementing an appropriate caching mechanism. The following consideration should be taken into account:

1) I can't use static class and methods.
2) There are around 6 instances (1 instance per class) per App Domain.

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C# - Class Structure With LINQ, Partial Classes, And Abstract Classes

May 17, 2010

I am following the Nerd Dinner tutorial as I'm learning ASP.NET MVC, and I am currently on Step 3: Building the Model. One part of this section discusses how to integrate validation and business rule logic with the model classes. All this makes perfect sense. However, in the case of this source code, the author only validates one class: Dinner.

What I am wondering is, say I have multiple classes that need validation (Dinner, Guest, etc). It doesn't seem smart to me to repeatedly write these two methods in the partial class:


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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