Why does DllImport not work for me?

C# Interview Questions and Answers

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146. Why does DllImport not work for me?

All methods marked with the DllImport attribute must be marked as public static extern.

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Other Interview Questions

• What's C#
• Is it possible to inline assembly or IL in C# code?
• Is it possible to have different access modifiers on the get/set methods of a property?
• Is it possible to have a static indexer in C#? allowed in C#.
• If I return out of a try/finally in C#, does the code in the finally-clause run?
• I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
• How does one compare strings in C#?
• How do you specify a custom attribute for the entire assembly (rather than for a class)?
• How do you mark a method obsolete?
• How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
• How do you directly call a native function exported from a DLL?
• How do I simulate optional parameters to COM calls?
• The C# keyword .int. maps to which .NET type?
• Which of these string definitions will prevent escaping on backslashes in C#?
• Which of these statements correctly declares a two-dimensional array in C#?
• If a method is marked as protected internal who can access it?
• What is boxing?
• What compiler switch creates an xml file from the xml comments in the files in an assembly?
• What is a satellite Assembly?
• What is a delegate?
• How does assembly versioning in .NET prevent DLL Hell?
• Which .Gang of Four. design pattern is shown below?
• In the NUnit test framework, which attribute must adorn a test class in order for it to be picked up by the NUnit GUI?
• Which of the following operations can you NOT perform on an ADO.NET DataSet?
• In Object Oriented Programming, how would you describe encapsulation?
• What do you know about .NET assemblies?
• What’s the difference between private and shared assembly?
• What’s a strong name?
• How can you tell the application to look for assemblies at the locations other than its own install?
• How can you debug failed assembly binds?
• Where are shared assemblies stored?
• How can you create a strong name for a .NET assembly?
• Where’s global assembly cache located on the system?
• Can you have two files with the same file name in GAC?
• So let’s say I have an application that uses MyApp.dll assembly ...
• What is delay signing?
• Is there an equivalent of exit() for quitting a C# .NET application?
• Can you prevent your class from being inherited and becoming a base class for some other classes?
• If a base class has a bunch of overloaded constructors ...
• I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
• How do I make a DLL in C#?
• How do I simulate optional parameters to COM calls?
• Will finally block get executed if the exception had not occurred?
• What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
• Is there regular expression (regex) support available to C# developers?
• Is there a way to force garbage collection?
• Does C# support properties of array types?
• What connections does Microsoft SQL Server support?
• What is a satellite assembly?
• How is method overriding different from overloading?
• When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
• Why would you use untrusted verificaion?
• What is the implicit name of the parameter that gets passed into the class set method?
• How do I register my code for use by classic COM clients?
• How do I do implement a trace and assert?
• How do I create a multilanguage, multifile assembly?
• C# provides a default constructor for me. I write a constructor that takes a string as a parameter ...
• What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
• Explain ACID rule of thumb for transactions.
• Where is the output of TextWriterTraceListener redirected?
• How do I create a multilanguage, single-file assembly?
• Why cannot you specify the accessibility modifier for methods inside the interface?
• Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
• Why do I get a syntax error when trying to declare a variable called checked?
• Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
• What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
• What does the keyword virtual mean in the method definition?
• What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
• How can I create a process that is running a supplied native executable (e.g., cmd.exe)?
• What is the difference between the System.Array.CopyTo() and System.Array.Clone()?
• How do I declare inout arguments in C#?
• Is there a way of specifying which block or loop to break out of when working with nested loops?
• What is the difference between const and static read-only?
• What does the parameter Initial Catalog define inside Connection String?
• What is the difference between System.String and System.StringBuilder classes?
• What is the top .NET class that everything is derived from?
• Can you allow class to be inherited, but prevent the method from being over-ridden?
• Can you change the value of a variable while debugging a C# application?
• Are private class-level variables inherited?
• Can you inherit multiple interfaces?
• From a versioning perspective, what are the drawbacks of extending an interface as opposed to extending a class?
• Which one is trusted and which one is untrusted?
• What namespaces are necessary to create a localized application?
• Does Console.WriteLine() stop printing when it reaches a NULL character within a string?
• What is the advantage of using System.Text.StringBuilder over System.String?
• What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
• Why do I get a security exception when I try to run my C# app?
• Is there any sample C# code for simple threading?
• What is the difference between // comments, /* */ comments and /// comments?
• What is the difference between and XML documentation tag?
• Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
• How do you inherit from a class in C#?
• How do I port "synchronized" functions from Visual J++ to C#?
• Can I define a type that is an alias of another type (like typedef in C++)?
• Is it possible to have different access modifiers on the get/set methods of a property?
• Is it possible to have a static indexer in C#?
• Does C# support #define for defining global constants?
• Does C# support templates?
• Does C# support parameterized properties?
• Does C# support C type macros?
• Can you store multiple data types in System.Array?
• Is it possible to inline assembly or IL in C# code?
• Can you declare the override method static while the original method is non-static?
• Does C# support multiple inheritance?
• Can multiple catch blocks be executed?
• Can you override private virtual methods?
• What is a pre-requisite for connection pooling?
• What is the data provider name to connect to Access database?
• Why does my Windows application pop up a console window every time I run it?
• What is the wildcard character in SQL?
• What is the role of the DataReader class in ADO.NET connections?
• What does the This window show in the debugger?
• Describe the accessibility modifier protected internal?
• What is an interface class?
• What is a multicast delegate?
• How does one compare strings in C#?
• What does assert() do?
• How do I get deterministic finalization in C#?
• How can I get around scope problems in a try/catch?
• Why do I get an error (CS1006) when trying to declare a method without specifying a return type?
• How do I convert a string to an int in C#?
• How do you directly call a native function exported from a DLL?
• What is the .NET datatype that allows the retrieval of data by a unique key?
• How do you specify a custom attribute for the entire assembly (rather than for a class)?
• What is the difference between a struct and a class in C#?
• What is the difference between the Debug class and Trace class?
• How can you overload a method?
• What debugging tools come with the .NET SDK?
• What does Dispose method do with the connection object?
• How do you generate documentation from the C# file commented properly with a command-line compiler?
• When you inherit a protected class-level variable, who is it available to?
• How can I get the ASCII code for a character in C#?
• How do I create a Delegate/MulticastDelegate?
• Is there an equivalent to the instanceof operator in Visual J++?
• How do destructors and garbage collection work in C#?
• My switch statement works differently! Why?
• How can I access the registry from C# code?
• How can you sort the elements of the array in descending order?
• How do you debug an ASP.NET Web application?
• How do you mark a method obsolete?
• How is the DLL Hell problem solved in .NET?
• What are the ways to deploy an assembly?
• Why does DllImport not work for me?
• What is a delegate?
• What is the difference between an interface and abstract class?
• What is an abstract class?
• Who is a protected class-level variable available to?
• Can you store multiple data types in System.Array?
• What’s the top .NET class that everything is derived from?
• What does the term immutable mean?
• What’s the difference between System.String and System.Text.StringBuilder classes?
• What’s the advantage of using System.Text.StringBuilder over System.String?
• What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
• How can you sort the elements of the array in descending order?
• What’s the .NET collection class that allows an element to be accessed using a unique key?
• What class is underneath the SortedList class?
• Will the finally block get executed if an exception has not occurred?­
• What’s the C# syntax to catch any possible exception?
• Can multiple catch blocks be executed for a single try statement?
• Explain the three services model commonly know as a three-tier application.
• What is the syntax to inherit from a class in C#?
• Can you prevent your class from being inherited by another class?
• Can you allow a class to be inherited, but prevent the method from being over-ridden?
• What’s an abstract class?
• When do you absolutely have to declare a class as abstract?
• What is an interface class?
• Why can’t you specify the accessibility modifier for methods inside the interface?
• What happens if you inherit multiple interfaces and they have conflicting method names?
• What’s the difference between an interface and abstract class?
• What is the difference between a Struct and a Class?
• What’s the implicit name of the parameter that gets passed into the set method/property of a class?
• What does the keyword “virtual” declare for a method or property?
• How is method overriding different from method overloading?
• Can you declare an override method to be static if the original method is not static?
• What are the different ways a method can be overloaded?
• If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
• What’s a delegate?
• What’s a multicast delegate?
• How do you generate documentation from the C# file commented properly with a command-line compiler?
• What debugging tools come with the .NET SDK?
• What does assert() method do?
• What’s the difference between the Debug class and Trace class?
• Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
• Where is the output of TextWriterTraceListener redirected?
• How do you debug an ASP.NET Web application?
• What are three test cases you should go through in unit testing?
• Can you change the value of a variable while debugging a C# application?
• What is the role of the DataReader class in ADO.NET connections?
• What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
• What is the wildcard character in SQL?
• Explain ACID rule of thumb for transactions.
• What connections does Microsoft SQL Server support?
• Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
• What does the Initial Catalog parameter define in the connection string?
• What does the Dispose method do with the connection object?
• What is a pre-requisite for connection pooling?
• How is the DLL Hell problem solved in .NET?
• What are the ways to deploy an assembly?
• What is a satellite assembly?
• What namespaces are necessary to create a localized application?
• What is the smallest unit of execution in .NET?
• When should you call the garbage collector in .NET?
• How do you convert a value-type to a reference-type?
• What happens in memory when you Box and Unbox a value-type?
• Difference between directcast and ctype.
• An example of a ctype and directcast.
• ctype(123.34,integer) - should it throw an error? Why or why not?
• directcast(123.34,integer) - should it throw an error? Why or why not?
• Difference between a sub and a function.
• Explain manifest & metadata.
• Difference between imperative and interrogative code.
• Difference between value and reference type.
• What are the two kinds of properties.
• Explain constructor.
• Describe ways of cleaning up objects.
• How can you clean up objects holding resources from within the code?
• Which controls do not have events?
• What is the maximum size of the textbox?
• Which property of the textbox cannot be changed at runtime?
• Which control cannot be placed in MDI?
• What is the difference between proc. sent BY VAL and BY SUB?