C# Discussion Boards - CodeProject

mark_w_14-Nov-08 5:11

mark_w_

14-Nov-08 5:11

Have a look at the compact database, offered by microsoft. Its free and is just a file that would be placed on a share that is backed up. You could then write a c# winform app to sit ontop of it.

It really depends where you skillset is, I would do the above, as i could do that quicker than using access (as i have not used access for a lonnnnng time)

Mark

Wendelius14-Nov-08 7:56

Wendelius

14-Nov-08 7:56

Why not use SQL Server Express Edition. If you build a totally new instance (on a separate machine), could the suppport be arranged since it's not disturbing any of the existing instances. Express edition is free and it's targeted for multi-user environments like Access, but has more capabilites (Compact edition cannot be used in multi user environments and all other editions aren't free to use).

Mika

The need to optimize rises from a bad design.

My articles[^]

Paul Conrad14-Nov-08 8:48

Paul Conrad

14-Nov-08 8:48

Use the Express edition of SQL Server. It should provide you plenty of functionality without having to deal with your IT not sharing their server.

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

"Not only do you continue to babble nonsense, you can't even correctly remember the nonsense you babbled just minutes ago." - Rob Graham

hellbentuk15-Nov-08 1:41

hellbentuk

15-Nov-08 1:41

Many thanks to you all..

Exception Constructor

George_George14-Nov-08 2:17

14-Nov-08 2:17

Hello everyone,

For the exception constructor,

Exception Constructor (SerializationInfo, StreamingContext)

http://msdn.microsoft.com/en-us/library/tz6bzkbf.aspx

I have two questions,

1. I saw some code defines it as public and some other code defines it as protected. What are the different purposes of different definitions?

2. I saw some code which defines a new exception type derives from System.Exception, and implements this contructor, but the implementation code is just call the base class constructor, and at the same time, the class is marked with Serializable tag. Like this.

I think such type of implementation is useless since the implementation of constructor is empty (just call base class contructor and the class is already marked with Serializable tag), so it is system default behavior and it should be ok to just mark it with Serializable tag to achieve the same effect.

Any comments?

[Serializable]
public class MyExceptionClass : Exception
{
    public MyExceptionClass (string errorMessage)
    {

    }

    public MyExceptionClass (SerializationInfo info, StreamingContext context) : base (nfo, context)
	{

	}
}

thanks in advance,
George

J4amieC14-Nov-08 2:23

J4amieC

14-Nov-08 2:23

George_George wrote:
Any comments?

Yes, as usual you need to read the documentation (In this case of SerializableAttribute, ISerializable and Exception).

George_George16-Nov-08 2:05

16-Nov-08 2:05

Thanks J4amieC,

I asked two questions. Your reply "yes" is for which one? Smile | :)

regards,
George

Le centriste14-Nov-08 5:44

Le centriste

14-Nov-08 5:44

You need to implement this constructor because constructors are not inherited.

George_George16-Nov-08 2:07

16-Nov-08 2:07

Thanks Le Centriste,

This constructor you mean "Exception Constructor (SerializationInfo, StreamingContext)"? Why you say "because constructors are not inherited"? When I inherit from a class, all public methods should be inherited and constructor is also inherited and could be called by base keywords. Any comments to clarify?

regards,
George

Le centriste16-Nov-08 2:33

Le centriste

16-Nov-08 2:33

All public and protected methods are inherited, except the constructors.

Suppose the following:

public class A
{
    public A()
    {
    }
}

public class B : A
{
    public B(int i)
    {
    }
}

A a = new A(); // Compiles OK
B b1 = new B(5); // Compiles OK
B b2 = new B(); // Compile error: No overload for method 'B' takes '0' arguments

If B does not define an empty constructor, it does not inherit it. There is one subtle thing happening here the compile does not tell you. Since B's only constructor does not specify which base class constructor to call, it calls A's empty costructor silently.

Consider the following code:

public class A
{
    public A(string s)
    {
    }
}

public class B : A
{
    public B(int i)
    {
    }
}

B b = new B(5); // Compile error: No overload for method 'A' takes '0' arguments

Since B does not specify which constructor from A to call, the compiler tries to place a call to A's empty constructor, but it does not exists, hence the error.

The following code would work:

public class A
{
    public A(string s)
    {
    }
}

public class B : A
{
    public B(int i) : base(i.ToString())
    {
    }
}

B b = new B(5); // Compiles OK

So, in your case, the base class defines a constructor for serialization, but you class does not inherit it.

George_George16-Nov-08 2:47

16-Nov-08 2:47

Thanks Le Centriste!

1.

You are so cool! I almost understand your points. Let me clarify. I think you mean even if the constructor in derived class MyException (below) did nothing but just do the same as base class, and if I do not include this constructor in derived class, it will hide the same signature constructor in base class, so that for an instance of derived class, we can not call this contructor (base constructor will not be called and found automatically, and base class constructor will be hide)?

public MyExceptionClass (SerializationInfo info, StreamingContext context)

2.

How about my question #1 in my original question? What is the difference between marking this contructor to be protected and to be public? Any special usage scenarios?

regards,
George

Le centriste16-Nov-08 2:54

Le centriste

16-Nov-08 2:54

1. You are on the right path.
2. A good case would be with abstract classes, where all constructors are made protected, because there is no point having public constructors in an abstract class.

George_George16-Nov-08 2:56

16-Nov-08 2:56

Thanks Le Centriste,

My class MyException is a class of the final level (e.g. be used by other components directly). I think I may be wrong. If I mark it as protected, during serialization, the constructor will not be called since from outside protected contructor could not be called?

regards,
George

N a v a n e e t h17-Nov-08 15:06

N a v a n e e t h

17-Nov-08 15:06

You can make the constructor protected only if you need to prevent access to this constructor from child classes. Else make it as public.

Navaneeth

How to use google | Ask smart questions

George_George18-Nov-08 2:21

18-Nov-08 2:21

Thanks Navaneeth,

If I mark the constructor as protected, I think it will be invoked when the instance is de-serialized, and since it is also protected, it means only the sub-class of this class is able to de-serialize the instance?

regards,
George

N a v a n e e t h14-Nov-08 17:36

N a v a n e e t h

14-Nov-08 17:36

The same question is answered many times in MSDN as well as here. Still you are not clear?

2 - Because the constructors are not inherited. So it allowes to pass the parameters when you are instantiating child class.

Navaneeth

How to use google | Ask smart questions

George_George16-Nov-08 2:08

16-Nov-08 2:08

Thanks Navaneeth!

Why you say "the constructors are not inherited"? When I inherit from a class, all public methods should be inherited and constructor is also inherited and could be called by base keywords. Any comments to clarify?

regards,
George

N a v a n e e t h16-Nov-08 3:35

N a v a n e e t h

16-Nov-08 3:35

George_George wrote:
Why you say "the constructors are not inherited"? When I inherit from a class, all public methods should be inherited and constructor is also inherited and could be called by base keywords. Any comments to clarify?

Here[^]

Navaneeth

How to use google | Ask smart questions

George_George16-Nov-08 3:40