c#英文面试 开发测试

1. Does C# support multiple inheritance?

No, use interfaces instead

2. What’s the implicit name of the parameter that gets passed into the class’ set method?

Value, and its datatype depends on whatever variable we’re changing

3. What’s the top .NET class that everything is derived from?

System.Object.

4. How’s method overriding different from overloading?

When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.

5. What is CLR?

The .NET Framework provides a runtime environment called the Common Language Runtime or CLR (similar to the Java Virtual Machine or JVM in Java), which handles the execution of code and provides useful services for the implementation of the program. CLR takes care of code management at program execution and provides various beneficial services such as memory management, thread management, security management, code verification, compilation, and other system services. The managed code that targets CLR benefits from useful features such as cross-language integration, cross-language exception handling, versioning, enhanced security, deployment support, and debugging.

6. What is CTS?

Common Type System (CTS) describes how types are declared, used and managed in the runtime and facilitates cross-language integration, type safety, and high performance code execution.

7. What is CLS?

The CLS is simply a specification that defines the rules to support language integration in such a way that programs written in any language, yet can interoperate with one another, taking full advantage of inheritance, polymorphism, exceptions, and other features. These rules and the specification are documented in the ECMA proposed standard document, "Partition I Architecture", http://msdn.microsoft.com/net/ecma

8. What is strong name?

A name that consists of an assembly's identity—its simple text name, version number, and culture information (if provided)—strengthened by a public key and a digital signature generated over the assembly.

9. What is Application Domain?

The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory. Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages.

10. What is serialization in .NET? What are the ways to control serialization?

Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database).Serialization can be defined as the process of storing the state of an object to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created. Binary serialization preserves type fidelity, which is useful for preserving the state of an object between different invocations of an application. For example, you can share an object between different applications by serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth. Remoting uses serialization to pass objects "by value" from one computer or application domain to another. XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful when you want to provide or consume data without restricting the application that uses the data. Because XML is an open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an attractive choice. There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.

11. What are Satellite Assemblies?

Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed.

12. What is Global Assembly Cache (GAC) and what is the purpose of it?

Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. You should share assemblies by installing them into the global assembly cache only when you need to.

13. What is Reflection in .NET?

All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.

14. What is the managed and unmanaged code in .net?

The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the execution of code and provides services that make the development process easier. Compilers and tools expose the runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that you develop with a language compiler that targets the runtime is called managed code; it benefits from features such as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment support, a simplified model for component interaction, and debugging and profiling services

15. What are Namespaces?

The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not modifiable.

16. What are the access-specifiers available in c#?

Private, Protected, Public, Internal, Protected Internal.

17. Advantage of ADO.Net?

    * ADO.NET Does Not Depend On Continuously Live Connections
    * Database Interactions Are Performed Using Data Commands
    * Data Can Be Cached in Datasets
    * Datasets Are Independent of Data Sources
    * Data Is Persisted as XML
    * Schemas Define Data Structures

 

18. Difference between OLEDB Provider and SqlClient ?

SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.

19. Differences between dataset.clone and dataset.copy?

Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints.Does not copy any data
Copy - Copies both the structure and data for this DataSet.

20. In a Webservice, need to display 10 rows from a table. So DataReader or DataSet is best choice?

WebService will support only DataSet.

21. What is Remoting?

The process of communication between different operating system processes, regardless of whether they are on the same computer. The .NET remoting system is an architecture designed to simplify communication between objects living in different application domains, whether on the same computer or not, and between different contexts, whether in the same application domain or not.

22. What’s the difference between System.String and System.StringBuilder classes?

System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

23. What’s a delegate?

A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

24. What’s an interface class?

It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes

 

比较全的C#英文面试题目及答案

General Questions Does C# support multiple-inheritance? No. Who is a protected class-level variable available to? It is available to any sub-class (a class inheriting this class). Are private class-level variables inherited? Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited. Describe the accessibility modifier “protected internal”. It is available to classes that are within the same assembly and derived from the specified base class. What’s the top .NET class that everything is derived from? System.Object. What does the term immutable mean? The data value may not be changed.  Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.    What’s the difference between System.String and System.Text.StringBuilder classes? System.String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created. Can you store multiple data types in System.Array? No. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array.  The CopyTo() method copies the elements into another existing array.  Both perform a shallow copy.  A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array.  A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods. What’s the .NET collection class that allows an element to be accessed using a unique key? HashTable. What class is underneath the SortedList class? A sorted HashTable. Will the finally block get executed if an exception has not occurred? Yes. What’s the C# syntax to catch any possible exception? A catch block that catches the exception of type System.Exception.  You can also omit the parameter data type in this case and just write catch {}. Can multiple catch blocks be executed for a single try statement? No. Once the proper catch block processed, control is transferred to the finally block (if there are any). Explain the three services model commonly know as a three-tier application. Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).    Class Questions What is the syntax to inherit from a class in C#? Place a colon and then the name of the base class. Example: class MyNewClass : MyBaseClass Can you prevent your class from being inherited by another class? Yes. The keyword “sealed” will prevent the class from being inherited. Can you allow a class to be inherited, but prevent the method from being over-ridden? Yes. Just leave the class public and make the method sealed. What’s an abstract class? A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation. When do you absolutely have to declare a class as abstract? 1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden. 2. When at least one of the methods in the class is abstract. What is an interface class? Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public, and are therefore public by default. Can you inherit multiple interfaces? Yes.  .NET does support multiple interfaces. What happens if you inherit multiple interfaces and they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay. To Do: Investigate What’s the difference between an interface and abstract class? In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed.  An abstract class may have accessibility modifiers. What is the difference between a Struct and a Class? Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval.  Another difference is that structs cannot inherit.    Method and Property Questions What’s the implicit name of the parameter that gets passed into the set method/property of a class? Value. The data type of the value parameter is defined by whatever data type the property is declared as.    What does the keyword “virtual” declare for a method or property? The method or property can be overridden. How is method overriding different from method overloading? When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.    Can you declare an override method to be static if the original method is not static? No. The signature of the virtual method must remain the same.  (Note: Only the keyword virtual is changed to keyword override)    What are the different ways a method can be overloaded? Different parameter data types, different number of parameters, different order of parameters. 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? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class. Events and Delegates What’s a delegate? A delegate object encapsulates a reference to a method. What’s a multicast delegate? A delegate that has multiple handlers assigned to it.  Each assigned handler (method) is called. XML Documentation Questions Is XML case-sensitive? Yes.    What’s the difference between // comments, /* */ comments and /// comments? Single-line comments, multi-line comments, and XML documentation comments. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with the /doc switch. Debugging and Testing Questions What debugging tools come with the .NET SDK? 1. CorDBG – command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch. 2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.    What does assert() method do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.    What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.    Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.    Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.    How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.    What are three test cases you should go through in unit testing? 1. Positive test cases (correct data, correct output). 2. Negative test cases (broken or missing data, proper handling). 3. Exception test cases (exceptions are thrown and caught properly).    Can you change the value of a variable while debugging a C# application? Yes. If you are debugging via Visual Studio.NET, just go to Immediate window.    ADO.NET and Database Questions What is the role of the DataReader class in ADO.NET connections? It returns a read-only, forward-only rowset from the data source.  A DataReader provides fast access when a forward-only sequential read is needed.    What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.    What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.    Explain ACID rule of thumb for transactions. A transaction must be: 1. Atomic - it is one unit of work and does not dependent on previous and following transactions. 2. Consistent - data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t. 3. Isolated - no transaction sees the intermediate results of the current transaction). 4. Durable - the values persist if the data had been committed even if the system crashes right after.    What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).    Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.    What does the Initial Catalog parameter define in the connection string? The database name to connect to.     What does the Dispose method do with the connection object? Deletes it from the memory. To Do: answer better. The current answer is not entirely correct.    What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical. Assembly Questions How is the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command. What is a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies. What namespaces are necessary to create a localized application? System.Globalization and System.Resources. What is the smallest unit of execution in .NET? an Assembly. When should you call the garbage collector in .NET? As a good rule, you should not call the garbage collector.  However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory.  However, this is usually not a good practice. How do you convert a value-type to a reference-type? Use Boxing. What happens in memory when you Box and Unbox a value-type? Boxing converts a value-type to a reference-type, thus storing the object on the heap.  Unboxing converts a reference-type to a value-type, thus storing the value on the stack.

 

http://www.c-sharpcorner.com/

 

 

1. What is the diff. between Test case & check list?

Test case is : How to test

CHeck list is: what to test

 

2. How do you handle conflict with programmers? （Testing）

Maintain a better relationship with the developers. Before raising the bug makes sure that the bug is a real & valid one. Don’t blame the developer for mistakes.

 

3.What is the difference between Whitebox Testing and Blackbox Testing?

whitbox testing that is related to structual knowledge whereas Blackbox Testing that is related to funtional knowledge

 

4.What is the difference between constructor and method?

a constructor is a method in the class which gets executed when its object is created. Usually, we put the initialization code in the constructor. Writing a constructor in the class is damn simple, have a look at the following sample:

public class Test

{

    public Test()

    {

        //Initilize code in the constructor.
    }
}

Constructors doesn't returns any value.

References and pointers cannot be used on constructors and destructors because their addresses cannot be taken. Constructors cannot be declared with the keyword virtual. If the constructors is defined as private, we can not create instance of that class.

 Method:

•  In methods we can define variables.These variables scope is within methods only.
• If you declare a public variable , it will be accessed in all mehtods.
• Methods may/maynot contains return type.
• Methods could be inhereted in derived class(Note That mehtod should be Public)

5. Difference between an abstract method & virtual method?

Virtual method has an implementation & provide the derived class with the option of overriding it. Abstract method does not provide an implementation & forces the derived class to override the method.

 

6. Difference between inheritance and polymorhism ?

Inheritance and Polymorphism are the two beasts of OOPs. Definition of Polymorphism: Mostly it is defined as 'To achieve multiple behaviours of the same variable' and it is achieved by using inheritance. So inheritance is the prerequisit of inheritance based Polymorphism. Difference between Inheritance and Polymorphism: In inheritance based polymorphism, common method(s) are defined in the base class and override them in the derived class with different implementation. So, now the challenge is to call the method of derived class with the base class object. To achieve the polymorphism, define an object variable of the base class and initialize it with a child class object. Whenever the method defined in the base class will be called, its implementation of child class will be called. Conclusion: In this way, we can build the better and scalable applications.