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How do you directly call a native function exported from a DLL?

Posted By :nishithraj     Posted Date :November 30, 2009    Points :10   Category :C# 
public static extern int MessageBoxA(int h, string m, string c, int type);

You can also find related Interview Question to How do you directly call a native function exported from a DLL?  below: 

Can I call a Win32 API function from a C# program?

Yes, you can.The .NET Framework provides a set of services called Platform Invoke, also known as PInvoke. Refer to the .NET Framework documentation for examples of using PInvoke services. (More...)

How can we call javascript function in page load event?

this.button.Attributes.Add("OnClick",return functionname(););

Why do we need to call CG.SupressFinalize?

Requests that the system not call the finalizer method for the specified object.

public static void SuppressFinalize(
object obj

The method removes obj from the set of objects that require finalization. The obj parameter is required to be the caller of this method.

Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it. (More...)

What is Method Overriding? How to override a function in C#?

Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new implementation of a member inherited from a base class. The method overridden by an override declaration is known as the overridden base method. The overridden base method must have the same signature as the override method.
You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override. (More...)

Can we call a base class method without creating instance?

Its possible If its a static method.

Its possible by inheriting from that class also.

Its possible from derived classes using base keyword. (More...)

Define precondition and post-condition to a member function.

A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold.
For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation.

A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false.
For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation. (More...)

Difference between a sub and a function.

A Sub Procedure is a method will not return a value
-A sub procedure will be defined with a "Sub" keyword
Sub ShowName(ByVal myName As String)
Console.WriteLine("My name is: " & myName)
End Sub
-A function is a method that will return value(s).
-A function will be defined with a "Function" keyword
Function FindSum(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
Dim sum As Integer = num1 + num2
Return sum
End Function (More...)

What is the Transport Protocol you use to call a Web Service ?

SOAP (Simple Object Access Protocol) is the preferred protocol. (More...)

Explain Virtual Function in C#.

Virtual functions implement the concept of polymorphism are the same as in C#, except that you use the override keyword with the virtual function implementaion in the child class.

The parent class uses the same virtual keyword. Every class that overrides the virtual method will use the override keyword.

class Shape{
public virtual void Draw()
{ Console.WriteLine("Shape.Draw") ; }
class Rectangle : Shape{
public override void Draw()
{ Console.WriteLine("Rectangle.Draw"); }
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How do I call a member method and pass a primitive type (Value Type) by reference?

Use the ref keyword when declaring the parameter of the method, for example:

public bool GetValue( ref int returnValue );

This will pass the numeric by reference.You can modify the value of returnValue within the body of GetValue and it will persist when the method call returns. (More...)

What is the difference between "using System.Data;" and directly adding the reference from "Add References Dialog Box"?

When you compiles a program using command line, u add the references using /r switch. When you compile a program using Visual Studio, it adds those references to our assembly, which are added using "Add Reference" dialog box. While "using" statement facilitates us to use classes without using their fully qualified names.

For example: if u have added a reference to "System.Data.SqlClient" using "Add Reference" dialog box then u can use SqlConnection class like this:


But if u add a "using System.Data.SqlClient" statement at the start of ur code then u can directly use SqlConnection class.

On the other hand if u add a reference using "using System.Data.SqlClient" statement, but don't add it using "Add Reference" dialog box, Visual Studio will give error message while we compile the program. (More...)

Which method would you call to send an e-mail message and wait for the transmission to complete before proceeding?

Select from following answers:


Correct Answer is:

SmtpClient.Send (More...)

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