Method Matching - C# Discussion Boards

Word Template Programming in C#

10-Mar-07 5:10

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Regards
Senthil [MVP - Visual C#]
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satsumatable9-Mar-07 17:36

satsumatable

9-Mar-07 17:36

Hi
I want to have a MS-WORD template and which should be taken as a input to the C# application. I will have some template variables in that template (.dot ) file those should be replaced during run time by the C# object. Please give some sample to work around this.

Thanks.

Method Matching

SHaroz9-Mar-07 17:20

SHaroz

9-Mar-07 17:20

Hello everyone,

I am trying to find all methods that have a particular signature. In other words, I want all methods that match the return type and parameter types of a specified method. I have a solution, but I was wondering if a more elegant approach exists. Using delegates is one possibility, but delegates are not very “edit-and-continue” friendly.

Here is my current solution:

void findSimilarMethods()
{
    MethodInfo example = this.GetType().GetMethod("ExampleMethod");
    ParameterInfo[] parameters = example.GetParameters();
    List<MethodInfo> matches = new List<MethodInfo>();

    MethodInfo[] methods = this.GetType().GetMethods();
    foreach (MethodInfo current in methods) {
        ParameterInfo[] currentParams = current.GetParameters();
        if ( current.ReturnType != example.ReturnType )
            continue;
        if ( currentParams.Length != parameters.Length )
            continue;
        if ( !ParameterEquality(parameters, currentParams) )
            continue;
        matches.Add(current);
    }
}

// a helper method to check parameter type equality
bool ParameterEquality(ParameterInfo[] a, ParameterInfo[] b)
{
    if (a.Length != b.Length)
        return false;
    for (int i = 0; i < a.Length; i++)
        if (a[i].GetType() != b[i].GetType())
            return false;
    return true;
}

Any suggestions would be greatly appreciated.

-Steve

Re: Method Matching

S. Senthil Kumar10-Mar-07 5:13

10-Mar-07 5:13

Why not use one of the other overloads of GetMethod MSDN[^], like the one that takes the method name and a Type [] for the parameters?

And you don't really need to match return type if you're matching parameter types, because you can't overload methods based on return type alone.

Regards
Senthil [MVP - Visual C#]
_____________________________
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Constructors in C#

Captain See Sharp9-Mar-07 15:57

9-Mar-07 15:57

Why is it that I can declare a constructor in a parent class as protected and then inherent that class and declare a constructor as public in the child class? However if I declare the parent's constructor as private I am unable to create any constructor at all in the child class. Why?

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Scott Dorman9-Mar-07 17:31

Scott Dorman

9-Mar-07 17:31

It has to do with the accessibility rules in C# and the meanings of private, protected, and public methods.

From the C# Language Reference[^]

The intuitive meaning of public is "access not limited".

The intuitive meaning of protected is "access limited to the containing class or types derived from the containing class".

The intuitive meaning of private is "access limited to the containing type".

When a type or member M is accessed, if M is protected, the access is permitted if it occurs within the class in which M is declared, or if it occurs within a class derived from the class in which M is declared and takes place through the derived class type (Section 3.5.3).

Otherwise, if M is private, the access is permitted if it occurs within the type in which M is declared.

As described in Section 3.4, all members of a base class, except for instance constructors, destructors and static constructors, are inherited by derived types. This includes even private members of a base class. However, the accessibility domain of a private member includes only the program text of the type in which the member is declared.

So, by declaring the constructor as "private", you are limiting it's accessibility to the class in which it is declared (the "containing type"). This effectively tells the compiler that since there is no default constructor accessible from outside the class, any derived classes cannot create an instance of their base class and, therefor, cannot themselves contain constructors.

By declaring the constructor as "protected", you are limiting it's accessibility to the class in which it is declared (the "containing type") and also to any types derived from that class. This effectively tells the compiler that the child classes are able to create an instance of their base class, and, therefor, can also contain constructors.

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Network integrated solutions

Zoltan Balazs10-Mar-07 1:59

Zoltan Balazs

10-Mar-07 1:59

The private constructor is intended:
- for classes that doesn't need to be created (provides only static methods)
- for implementing the singleton pattern

Also check out the constructor usage guidelines [^]

Anyway why would you derive a class with private constructor and instantiate that?

Captain See Sharp10-Mar-07 13:42

10-Mar-07 13:42

Zoltan Balazs wrote:
Anyway why would you derive a class with private constructor and instantiate that?

I wouldn't, at least I can't see any situation where I would need to do that right now. I just want to try to understand every nook and cranny of the C# language and the CLR. Sometimes I get a very simple question stuck in my head and I am not satisfied until I figure it out. A lot of times these questions have to do with object-oriented concepts.

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S. Senthil Kumar10-Mar-07 5:20

10-Mar-07 5:20

Well, any constructor you create in the child class will call the base class constructor - and fail because you've declared it as private. It's just like some external class attempting to instantiate and therefore call the private constructor.

If you're not clear why a derived class's constructor must call a base class one, take a look at this example

class Base
{
   public int x;

   public Base() { x = 20; }
}

class Derived : Base
{
   public Derived() {}
}

Now if you run the following snippet of code

Derived d  = new Derived();
Console.WriteLine(d.x);

What value do you expect? 20, because Derived after all, is a Base. If Derived's constructor did not call the Base one, then the above snippet will give x's default value instead.

Regards
Senthil [MVP - Visual C#]
_____________________________
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Captain See Sharp10-Mar-07 13:37

10-Mar-07 13:37

Are you saying that the C# compiler implicitly calls the base's constructor? I thought you had to explicitly do that.

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S. Senthil Kumar10-Mar-07 13:46

10-Mar-07 13:46

Captain See Sharp wrote:
Are you saying that the C# compiler implicitly calls the base's constructor?

Yes, it attempts to call the base class's default constructor, if you don't make an explicit call. That's why you'll see code like this fail to compile

class Base
{
   public Base(int x){}
}

class Derived : Base
{
   public Derived() {} // won't compile, as compiler attempts to call Base() and
                       // no default constructor exists.
}

Regards
Senthil [MVP - Visual C#]
_____________________________
My Blog | My Articles | My Flickr | WinMacro

Captain See Sharp10-Mar-07 13:51

10-Mar-07 13:51

S. Senthil Kumar wrote:
That's why you'll see code like this fail to compile

I see, I thought C# always created a default parameterless constructor, I tested it and you are right, it does not compile.

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gumi_r@msn.com10-Mar-07 14:29

gumi_r@msn.com

10-Mar-07 14:29

It will always create a default parameterless public constructor unless you define your own constructor(s). That's why when you want to create a purely static class, you explicitly define a private constructor (typically parameterless)...that way you avoid having a default public constructor and therefore your class has no accesible constructors at all. If you dont explicitly add this private constructor your class would automatically have the default public one and consumers would be able to instantiate it.

And yes, any derived class constructor will attempt to call the default constructor of it's base class if no other constructor of said base class is explicitly called in your code.

Captain See Sharp10-Mar-07 13:54

10-Mar-07 13:54

Another question. The child class only implicitly calls the base's parameterless constructor right? If it does this, will it call the parent's parameterless constructor for all of the child's constructors if you do not explicitly call a specific base constructor?

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S. Senthil Kumar10-Mar-07 14:21

adding a property to user control

10-Mar-07 14:21

Captain See Sharp wrote:
will it call the parent's parameterless constructor for all of the child's constructors if you do not explicitly call a specific base constructor?

Yes, it will.

Regards
Senthil [MVP - Visual C#]
_____________________________
My Blog | My Articles | My Flickr | WinMacro

State Mangement

Renuka Reddy9-Mar-07 15:33

Renuka Reddy

9-Mar-07 15:33

what is mean of state management...
where we r using.....
which purpose.....
please give me detailed...

Re: State Mangement

Udhaya Kumar.D10-Mar-07 4:19

Udhaya Kumar.D

10-Mar-07 4:19

State Management is used in ASP.NET 2.0. It provides a variety of mechanisms for building stateful Web applications. This module introduces view state, application cache, session state, profiles, and cookies.

dino20949-Mar-07 12:57

dino2094

9-Mar-07 12:57

I have a user control inherited from a Panel. I'm trying to make it re sizable and movable(mostly done)

I'd like to add a property to be able to lock the width or height or both.

I'm not sure how to do it. The code below kind of gives the feeling of what I'm trying to do.

Once again, my thanks goes out to this great board and its members.

  <br />
<br />
public partial class PanelSizable : System.Windows.Forms.Panel<br />
    {<br />
<br />
        enum LockedType<br />
        {<br />
            Both,<br />
            Width,<br />
               Height,<br />
            None<br />
        };<br />
<br />
    <br />
<br />
        private LockedType lockStatus = LockedType.None;<br />
<br />
        public LockedType LockSize<br />
        {<br />
            get         {                return lockStatus;          }<br />
            set            {              lockStatus = value;        }<br />
<br />
}<br />
<br />
....<br />

Re: adding a property to user control

Captain See Sharp9-Mar-07 16:06