Polymorphism is when a class can be used as more than one type through inheritance. It can be used as its own type, any base types, or any interface type if it implements interfaces.
It can be achieved in the following ways:
Derived class inherits from a base class and it gains all the methods, fields, properties and events of the base class.
To completely take over a class member from a base class, the base class has to declare that member as virtual.
Monday, August 1, 2011
How to achieve polymorphism in C#.NET?
Polymorphism is when a class can be used as more than one type through inheritance. It can be used as its own type, any base types, or any interface type if it implements interfaces.
It can be achieved in the following ways:
Derived class inherits from a base class and it gains all the methods, fields, properties and events of the base class.
To completely take over a class member from a base class, the base class has to declare that member as virtual.
It can be achieved in the following ways:
Derived class inherits from a base class and it gains all the methods, fields, properties and events of the base class.
To completely take over a class member from a base class, the base class has to declare that member as virtual.
What benefit do you get from using a Primary Interop Assembly (PIA)?
A primary interop assembly contains type definitions (as metadata) of types implemented with COM.
Only a single PIA can exist, which needs to be signed with a strong name by the publisher of the COM type library.
One PIA can wrap multiple versions of the same type library.
A COM type library imported as an assembly can be a PIA only if it has been signed and published by the same publisher.
Therefore, only the publisher of a type library can produce a true PIA, that can be considered as the unit of an official type definition for interoperating with the underlying COM types.
Only a single PIA can exist, which needs to be signed with a strong name by the publisher of the COM type library.
One PIA can wrap multiple versions of the same type library.
A COM type library imported as an assembly can be a PIA only if it has been signed and published by the same publisher.
Therefore, only the publisher of a type library can produce a true PIA, that can be considered as the unit of an official type definition for interoperating with the underlying COM types.
What is the use of GetCommandLineArgs() method in C#.NET?
With GetCommandLineArgs() method, the command line arguments can be accessed.
The value returned is an array of strings.
The value returned is an array of strings.
Explain the use of virtual, sealed, override, and abstract.
The virtual keyword enables a class to be overridden. If it has to be prevented from being overridden, then the sealed keyword needs to be used. If the keyword virtual is not used, members of the class can even then be overridden. However, its usage is advised for making the code meaningful.
The override keyword is used to override the virtual method in the base class. Abstract keyword is used to modify a class, method or property declaration. You cannot instantiate an abstract class or make calls to an abstract method directly.
An abstract virtual method means that the definition of the method needs to be given in the derived class.
The override keyword is used to override the virtual method in the base class. Abstract keyword is used to modify a class, method or property declaration. You cannot instantiate an abstract class or make calls to an abstract method directly.
An abstract virtual method means that the definition of the method needs to be given in the derived class.
Explain the use of virtual, sealed, override, and abstract.
The virtual keyword enables a class to be overridden. If it has to be prevented from being overridden, then the sealed keyword needs to be used. If the keyword virtual is not used, members of the class can even then be overridden. However, its usage is advised for making the code meaningful.
The override keyword is used to override the virtual method in the base class. Abstract keyword is used to modify a class, method or property declaration. You cannot instantiate an abstract class or make calls to an abstract method directly.
An abstract virtual method means that the definition of the method needs to be given in the derived class.
The override keyword is used to override the virtual method in the base class. Abstract keyword is used to modify a class, method or property declaration. You cannot instantiate an abstract class or make calls to an abstract method directly.
An abstract virtual method means that the definition of the method needs to be given in the derived class.
What are Extender provider components? Explain how to use an extender provider in the project.
An extender provider is a component that provides properties to other components.
Implementing an extender provider:
•Use the ProvidePropertyAttribute, which specifies the name of the property that an implementer of IExtenderProvider provides to other components, attribute to specify the property provided by your extender provider.
•Implement the provided property.
•Track which controls receive your provided property.
•Implement the IExtenderProvider, which defines the interface for extending properties to other components in a containe, interface.
Implementing an extender provider:
•Use the ProvidePropertyAttribute, which specifies the name of the property that an implementer of IExtenderProvider provides to other components, attribute to specify the property provided by your extender provider.
•Implement the provided property.
•Track which controls receive your provided property.
•Implement the IExtenderProvider, which defines the interface for extending properties to other components in a containe, interface.
What are circular references? Explain how garbage collection deals with circular references.
A circular reference is a run-around wherein the 2 or more resources are interdependent on each other rendering the entire chain of references to be unusable.
There are quite a few ways of handling the problem of detecting and collecting cyclic references.
1. A system may explicitly forbid reference cycles.
2. Systems at times ignore cycles when they have short lives and a small amount of cyclic garbage. In this case a methodology of avoiding cyclic data structures is applied at the expense of efficiency.
3. Another solution is to periodically use a tracing garbage collector cycles.
Other types of methods to deal with cyclic references are:
•Weighted reference counting
•Indirect reference counting
There are quite a few ways of handling the problem of detecting and collecting cyclic references.
1. A system may explicitly forbid reference cycles.
2. Systems at times ignore cycles when they have short lives and a small amount of cyclic garbage. In this case a methodology of avoiding cyclic data structures is applied at the expense of efficiency.
3. Another solution is to periodically use a tracing garbage collector cycles.
Other types of methods to deal with cyclic references are:
•Weighted reference counting
•Indirect reference counting
Change date format mm/dd/yy to dd/mm/yy using query?
Select CAST(DAY(GETDATE()) AS VARCHAR(2)) + ‘/’ + CAST(MONTH(GETDATE()) AS VARCHAR(2)) + ‘/ ‘ + CAST(YEAR(GETDATE()) AS VARCHAR(4)) AS DATE
Can you declare the override method static while the original method is non-static?
No, you can’t the signature of the virtual method must remain the same, only the keyword ‘virtual is changed to keyword override’.
Is it possible to insert hyperlinks in ListBox?
It can’t possible adding hyperlinks/links to listbox.
Its just a collection items not child items and are not render while anyone put some html tags. So, its not possible
Its just a collection items not child items and are not render while anyone put some html tags. So, its not possible
How can I get the date of Last Monday of specified week?
declare @dt datetime
set @dt=’1/1/2010′ –Want to know January’s Last Monday Date
SELECT dateadd(d,-datepart(dw,DATEADD(d, -datepart(d,dateadd(mm,1,@dt)),dateadd(mm,1,@dt))-1)+1,DATEADD(d, -datepart(d,dateadd(mm,1,@dt)),dateadd(mm,1,@dt)))
set @dt=’1/1/2010′ –Want to know January’s Last Monday Date
SELECT dateadd(d,-datepart(dw,DATEADD(d, -datepart(d,dateadd(mm,1,@dt)),dateadd(mm,1,@dt))-1)+1,DATEADD(d, -datepart(d,dateadd(mm,1,@dt)),dateadd(mm,1,@dt)))
Can we store filtered DataView in ViewState?
We can store only objects of the following types:
1. string
2. integers
3. boolean
4. Array
5. ArrayList
6. Hash tables
7. Custom types etc.
Apart from above we can share some other types too but the class must be serialized.
In view of above theory, we can say ‘yes, we can store DataView in ViewState for serialized class.
1. string
2. integers
3. boolean
4. Array
5. ArrayList
6. Hash tables
7. Custom types etc.
Apart from above we can share some other types too but the class must be serialized.
In view of above theory, we can say ‘yes, we can store DataView in ViewState for serialized class.
Can I inherit two difference classes to partial classes?
We can’t inherit two difference classes to partial class because in C# multiple inheritance is not possible using classes.
What are Classes and structures
Structures
A structure in C# is simply a composite data type [you are well aware from composite data type, refer to data types for more details], which consists number of members of other types. The structure define simply by using the struct keyword.
eg. struct enroll
{
public string name, fname, mname;
public string char sex;
Public int age;
public string address;
}
Classes
It is cleared from above study that Classes are reference type. A class is a collection of its data members. Data members are those members of class which contains the data of class like fields, constants and events etc. Class is declared simply just followed by class keyword with optional modifiers; by default C# classes are public.
eg. class myClass
{
public int xyz;
public string name;
public const int y=22;
}
A structure in C# is simply a composite data type [you are well aware from composite data type, refer to data types for more details], which consists number of members of other types. The structure define simply by using the struct keyword.
eg. struct enroll
{
public string name, fname, mname;
public string char sex;
Public int age;
public string address;
}
Classes
It is cleared from above study that Classes are reference type. A class is a collection of its data members. Data members are those members of class which contains the data of class like fields, constants and events etc. Class is declared simply just followed by class keyword with optional modifiers; by default C# classes are public.
eg. class myClass
{
public int xyz;
public string name;
public const int y=22;
}
Define interface in own words
An interface is simply a collection of function prototypes. An Interface is a reference type like a class, but interface can contain only abstract members. In other words, Interface is a contract that defines the signature of the functionality.
An interface looks like a class definitions, but its only purpose is to define a set of methods and not to implement them. For this reason the interface definition includes only the definition of methods [in other words the abstract methods]. Interface contains only methods, properties and delegates but can not contain fields, constructors, destructor and any type of static members.
An interface looks like a class definitions, but its only purpose is to define a set of methods and not to implement them. For this reason the interface definition includes only the definition of methods [in other words the abstract methods]. Interface contains only methods, properties and delegates but can not contain fields, constructors, destructor and any type of static members.
Tuesday, July 12, 2011
Download Image from URL
public System.Drawing.Image DownloadImageFromUrl(string imageUrl)
{
System.Drawing.Image image = null;
try
{
System.Net.HttpWebRequest webRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(imageUrl);
webRequest.AllowWriteStreamBuffering = true;
webRequest.Timeout = 30000;
System.Net.WebResponse webResponse = webRequest.GetResponse();
System.IO.Stream stream = webResponse.GetResponseStream();
image = System.Drawing.Image.FromStream(stream);
webResponse.Close();
}
catch (Exception ex)
{
return null;
}
return image;
}
protected void btnSave_Click(object sender, EventArgs e)
{
System.Drawing.Image image = DownloadImageFromUrl(txtUrl.Text.Trim());
string rootPath = @"C:\DownloadedImageFromUrl";
string fileName = System.IO.Path.Combine(rootPath, "test.gif");
image.Save(fileName);
}
{
System.Drawing.Image image = null;
try
{
System.Net.HttpWebRequest webRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(imageUrl);
webRequest.AllowWriteStreamBuffering = true;
webRequest.Timeout = 30000;
System.Net.WebResponse webResponse = webRequest.GetResponse();
System.IO.Stream stream = webResponse.GetResponseStream();
image = System.Drawing.Image.FromStream(stream);
webResponse.Close();
}
catch (Exception ex)
{
return null;
}
return image;
}
protected void btnSave_Click(object sender, EventArgs e)
{
System.Drawing.Image image = DownloadImageFromUrl(txtUrl.Text.Trim());
string rootPath = @"C:\DownloadedImageFromUrl";
string fileName = System.IO.Path.Combine(rootPath, "test.gif");
image.Save(fileName);
}
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