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A good design to pack parameters?

I have an object that takes plenty of parameters to its constructor (from 9 to 13 depending on use).
I want to avoid the ugliness of new MyObject(param1, param2, param3 ... param13).
My first attempt was to create a class MyObjectParams with properties with public getters and setters, it gives something like that :
var objectParams = new MyObjectParams
{
Param1 = ...,
Param2 = ...,
...
};
I see some big projects like SlimDX for their PresentParameters use this design. It looks better. But the class is not immutable.
I'd like my MyObjectParams to be immutable while still using a clean construction style. This is how it would look like with an immutable class :
var objectParams = new MyObjectParams
(
param1,
param2,
...
);
Note: it's just the long constructor line broken into several, so it's cleaner but still not as readable as initializers.
I was thinking of using named parameters to get both an immutable class and a more or less clean code, but I'm not sure whether this actually is a good idea:
var objectParams = new MyObjectParams
(
param1: ...,
param2: ...,
...
);
Should I use named parameters? Can you think of a better approach to solve this problem?
Edited regarding an answer below: unfortunately, I don't really think the design is bad. The 9 parameters really are required and remain constant throughout the entire life of the object. I cannot provide a default value for them as it is completely usage-dependant.

Have you looked into designing a solution in which you wouldn't need this amount of parameters? Having a lot of parameters makes the code very tightly coupled which reduces maintainability. Maybe you can redesign a small amount of code to a design which better separates the responsibilities of the class?

I really like the way The Zen of Python says a few things:
Simple is better than complex.
Complex is better than complicated.
[...]
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
I believe that having a dedicated Options class of some kind with the exhaustive list of all possible parameters is a good idea. Allow your MyObject constructor to require an Options instance, and then store a reference to the instance as a field on MyObject and refer to its getters/setters. (Storing the reference will be much superior to trying to parse the options and transfer their values to the MyObject instance. Now that would be messy.) With all data access delegated to the Options class, you will have successfully encapsulated the object's configuration, and you've designed a simple API for option access as the same time.
If Options has no reason to be publicly accessible, make it a private class definition and then you're free to maintain changes to Options logic without modifying MyObject. I believe that is a fair solution to you as the developer, and doesn't commit atrocities.

The constructor could have only a small number of parameters, the ones required for proper object initialization. You could then have a number of properties that can be set after the object has been constructed. You can set default values for those properties in the constructor and the client can set the ones he/she requires.
class Person
{
public Person(string name, int age)
{
Name = name;
Age = age;
Address = "Unknown";
Email = "Unknown";
}
public string Name {get; private set;}
public int Age {get; private set;}
public string Email {get; set;}
public string Address {get; set;}
}
Person p = new Person("John Doe", 30);
p.Email = "john.doe#example.org";

You could use the builder pattern to construct an immutable object.
public sealed class ComplexObject
{
public int PropA { get; private set; }
public string PropB { get; private set; }
public sealed class Builder
{
int _propA;
string _propB;
public Builder SetPropA(int propA)
{
// validate
_propA = propA;
return this;
}
public Builder SetPropB(string propB)
{
// validate
_propB = propB;
return this;
}
public CustomObject ToCustomObject()
{
return new CustomObject
{
PropA = _propA,
PropB = _propB
};
}
}
}
Usage
var custom =
new CustomObject.Builder()
.SetPropA(1)
.SetPropB("Test")
.ToCustomObject();
Final Thoughts
Despite my previous suggestion I am in no way against using named parameters if they are available.

C# Return Value, But keep getting error. Why?

Hello fellow stackoverflow members!
I'm very new to the C# language transfer from Java, Obj-C.
It looks pretty same as Java, but I have trouble issue in very simple thing.
I have created two individual class files, Class-A and Class-Human.
Specification for Class-A
it contains the static main method declared.And I've tried to create the new instance of Class-Human.
public static void main(String args[])
{
Human human = new Human("Yoon Lee", 99);
int expected = human.getNetID; //<-gets the error at this moment.
}
Specification for Class-Human
namespace Class-A
{
public class Human
{
public String name;
public int netId;
public Human(String name, int netId)
{
this.name = name;
this.netId = netId;
}
public int getNetID()
{
return netId;
}
}
Why can't copy over into local variable?
The compiler prompts me the error of
'Cannot convert method group of 'getNetID' delegate blah blah'
Thank you.

Change the method-call to:
int expected = human.getNetID();
In C#, method-calls require parantheses () containing a comma-separated list of arguments. In this case, the getNetID method is parameterless; but the empty parantheses are still required to indicate that your intention is to invoke the method (as opposed to, for example, converting the method-group to a delegate-type).
Additionally, as others have pointed out, there is a mismatch betweem the return-type of the method and the variable you're assigning its value to, which you're going to have to resolve somehow (change both the field-type and method return-type to int / parse the string as an integer, etc.).
On another note, C# natively supports properties for getter-setter semantics, so the idiomatic way of writing this would be something like:
//hyphens are not valid in identifiers
namespace ClassA
{
public class Human
{
// these properties are publicly gettable but can only be set privately
public string Name { get; private set; }
public int NetId { get; private set; }
public Human(string name, int netId)
{
this.Name = name;
this.NetId = netId;
}
// unlike Java, the entry-point Main method begins with a capital 'M'
public static void Main(string[] args)
{
Human human = new Human("Yoon Lee", 99);
int expected = human.NetId; // parantheses not required for property-getter
}
}
}

You're trying to use a method as if it's a property. You need parenthesis and to convert the string to int, or just make getNetID return an int.
I think you meant:
public int getNetID()
{
return netId;
}
Or better still, use automatic properties:
public int NetId {get; private set;} //Notice Making N in Net capital
And then:
int expected = human.getNetID();
This will do the trick (-:

It should be human.getNetID()
Edit: And yes, as Oren says - you should change your netId getter to return int. I assume that is what you want to do.

I see that netId is integer.
getNetID() return type is string.
return type is not matching.

netID is declared as an Int:
public int netId;
but your function getNetID returns a string:
public String getNetID()
Therefore, the body of getNetID makes no sense when it tried to return an int as a string:
return netId;

Human human = new Human("Yoon Lee", 99);
int expected = human.getNetID(); //<-gets the error at this moment.
you need to add parentheses after the method call.
The way you have it right now you are fetcing the function itself.

Dynamic Linq Library Help

I have the following class:
public class Item
{
public Dictionary<string, string> Data
{
get;
set;
}
}
and a list of it:
List<Item> items;
I need to filter and order this list dynamically using SQL-Like strings. The catch is, that I need to order it by the Data dictionary.
For example: Order By Data["lastname"] or Where Data["Name"].StartsWith("a"). I thought to use the dynamic linq library, but is there any way that my clients can write without the Data[]? For example:
Name.StartsWith("abc")
instead of
Data["Name"].StartsWith("abc")
?

You could add a property like this:
public class Item
{
public Dictionary<string, string> Data
{ get; set; }
public string Name { get { return Data["lastname"]; } }
}
//Call by: i.Name.StartsWith("abc");
Or an extension method:
public static class ItemExtensions
{
public static string Name(this Item item)
{
return item.Data["lastname"];
}
}
//Call by: i.Name().StartsWith("abc");
Or if it's a very commonly used method, you could add something like a .NameStartsWith():
public static string NameStartsWith(this Item item, stirng start)
{
return item.Data["lastname"].StartsWith(start);
}
//Call by: i.NameStartsWith("abc");

This doesn't have anything to do with the Linq Dynamic Query unit. That unit is for when you have actual fields/properties and the names of them will be given to you at runtime. In other words, you have a class like this:
public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
And you want to be able to write a query like this:
var sortedPeople = people.OrderBy("FirstName");
You are trying to do the exact opposite of this - you have a class that does not have any actual properties, just an attribute dictionary, and you want compile-time safety. You can't have it; there's no way to guarantee that an item will be in the dictionary, especially when the dictionary is public and anyone can add/remove directly from it!
If there's some reason that you must use that specific class design, then you could conceivably write some wrappers as Nick has presented, but I wouldn't even bother - they're not actually providing any encapsulation because the Data dictionary is still wide open to the whole world. Instead, I would just provide a single safe getter method or indexer property and create a few constants (or an enum) with the names of properties you expect to be in there.
public class Item
{
public Dictionary<string, string> Data { get; set; }
public string GetValue(string key)
{
if (Data == null)
return null;
string result;
Data.TryGetValue(key, out result);
return result;
}
}
public class ItemKeys
{
public const string Name = "Name";
public const string Foo = "Foo";
}
And so on. Really the ItemKeys isn't that important, the safe GetValue method is what's important, because otherwise you run the risk of a NullReferenceException if Data hasn't been assigned, or a KeyNotFoundException if even one Item instance doesn't have that property. Using the GetValue method here will succeed no matter what:
var myItems = items.OrderBy(i => i.GetValue(ItemKeys.Name));
If you find you're writing a lot of repetitive code for the same attributes, then start worrying about adding shortcut properties or extension methods to the class.

I assume that you don't know the names of the properties at compile-time (in which case, you could simply define properties and wouldn't have this problem). I have two suggestions that you could try, but I didn't implement any of them myself, so I can't guarantee that it will work.
If you can use .NET 4.0, you could inherit from DynamicObject and implement TryGetMember method (which is called when you use o.Foo on an object that is declared as dynamic). Assuming that Dynamic LINQ works with DLR, it should automatically invoke this method for objects that inherit from DynamicObject. Inside the TryGetMember method, you would get a name of the accessed property, so you could perform a dictionary lookup. (However, this solution would work only if Dynamic LINQ integrates well with DLR).
In any case, you could do some basic parsing of the string entered by the user and replace for example Name with Data["Name"]. This would definitely work, but it may be a bit difficult (because you should probably at least check that you're doing the replace in correct context - e.g. not inside a string constant).
Regarding extension methods - I'm not sure if Dynamic LINQ handles extension methods (but, I don't think so, because that would require searching all referenced assemblies)

Dot notation for hierarchical related string values

I have a lot of constant string values in my application which I want to have as strongly typed objects in C# for code reuse and readability. I would like to be able to reference the string value like so:
Category.MyCategory //returns a string value ie “My Category”
Category.MyCategory.Type.Private //returns a string value ie “private”
Category.MyCategory.Type.Shared //returns a string value ie “shared”
I have started by implementing the following classes each containing a list of public string valued fields with a public property which exposes the child.
Category, MyCategory, Type
However I already know this is not the way to go so could do with a bit of advice on this one.
An example of this is where I am using the Syndication classes to add a category to an atom feed. I am creating the items in this feed dynamically so need to use the notation as shown.
item.Categories.Add( new SyndicationCategory
{
Scheme = Category.PersonType,
Label="My Category",
Name=Category.MyCategory.Type.Private
});

Keep your string constants close to where you need them, IMO having a class that just declares constants is an OO antipattern

Why not simply implement them as classes with overridden ToString implementations?
public class MyCategory
{
private readonly MyType type;
public MyCategory()
{
this.type = new MyType();
}
public MyType Type
{
get { return this.type; }
}
// etc.
public override string ToString()
{
return "My Category";
}
}
public class MyType
{
public override string ToString()
{
return "My Type";
}
// more properties here...
}
However, for general purposes, consider whether the strings in themselves don't represent concepts that are better modeled as full-blown objects.

I completely agree with Rob. If you still want to have a "bag of strings", you could try using nested classes, something like below. I don't really like it, but it works.
public class Category
{
public class MyCategory
{
public const string Name = "My Category";
public class Type
{
public const string Private = "private";
public const string Shared = "shared";
}
}
}

Constructors with the same argument type

I have a Person object with two constructors - one takes an int (personId), the other a string (logonName). I would like another constructor that takes a string (badgeNumber). I know this can't be done, but seems it might be a common situation. Is there a graceful way of handling this? I suppose this would apply to any overloaded method. Code:
public class Person
{
public Person() {}
public Person(int personId)
{
this.Load(personId);
}
public Person(string logonName)
{
this.Load(logonName);
}
public Person(string badgeNumber)
{
//load logic here...
}
...etc.

You could perhaps use factory methods instead?
public static Person fromId(int id) {
Person p = new Person();
p.Load(id);
return p;
}
public static Person fromLogonName(string logonName) {
Person p = new Person();
p.Load(logonName);
return p;
}
public static Person fromBadgeNumber(string badgeNumber) {
Person p = new Person();
// load logic
return p;
}
private Person() {}

You might consider using custom types.
For example, create LogonName and BadgeNumber classes.
Then your function declarations look like...
public Person(LogonName ln)
{
this.Load(ln.ToString());
}
public Person(BadgeNumber bn)
{
//load logic here...
}
Such a solution might give you a good place to keep the business logic that governs the format and usage of these strings.

You have four options that I can think of, three of which have already been named by others:
Go the factory route, as suggested by several others here. One disadvantage to this is that you can't have consistent naming via overloading (or else you'd have the same problem), so it's superficially less clean. Another, larger, disadvantage is that it precludes the possibility of allocating directly on the stack. Everything will be allocated on the heap if you take this approach.
Custom object wrappers. This is a good approach, and the one I would recommend if you are starting from scratch. If you have a lot of code using, e.g., badges as strings, then rewriting code may make this a non-viable option.
Add an enumeration to the method, specifying how to treat the string. This works, but requires that you rewrite all the existing calls to include the new enumeration (though you can provide a default if desired to avoid some of this).
Add a dummy parameter that is unused to distinguish between the two overloads. e.g. Tack a bool onto the method. This approach is taken by the standard library in a few places, e.g. std::nothrow is a dummy parameter for operator new. The disadvantages of this approach are that it's ugly and that it doesn't scale.
If you already have a large base of existing code, I'd recommend either adding the enumeration (possibly with a default value) or adding the dummy parameter. Neither is beautiful, but both are fairly simple to retrofit.
If you are starting from scratch, or only have a small amount of code, I'd recommend the custom object wrappers.
The factory methods would be an option if you have code which heavily uses the raw badge/logonName strings, but doesn't heavily use the Person class.

No.
You might consider a flag field (enum for readability) and then have the constructor use htat to determine what you meant.

That won't work. You might consider making a class called BadgeNumber that wraps a string in order to avoid this ambiguity.

You cannot have two different constructors/methods with the same signature, otherwise, how can the compiler determine which method to run.
As Zack said, I would consider creating an "options" class where you could actually pass the parameters contained in a custom type. This means you can pretty much pass as many parameters as you like, and do what you like with the options, just be careful you dont create a monolithic method that tries to do everything..
Either that, or vote for the factory pattern..

You could use a static factory method:
public static Person fromLogon(String logon) { return new Person(logon, null); }
public static Person fromBadge(String badge) { return new Person(null, badge); }

As has been suggested, custom types is the way to go in this case.

If you are using C# 3.0, you can use Object Initializers:
public Person()
{
}
public string Logon { get; set; }
public string Badge { get; set; }
You would call the constructor like this:
var p1 = new Person { Logon = "Steve" };
var p2 = new Person { Badge = "123" };

Only thing I can think of to handle what you're wanting to do is to have to params, one that describes the param type (an enum with LogonName, BadgeNumer, etc) and the second is the param value.

You could switch to a factory style pattern.
public class Person {
private Person() {}
public static PersonFromID(int personId)
{
Person p = new Person().
person.Load(personID);
return p;
this.Load(personId);
}
public static PersonFromID(string name)
{
Person p = new Person().
person.LoadFromName(name);
return p;
}
...
}
Or, as suggested, use custom types. You can also hack something using generics, but I wouldn't recommend it for readability.

Depending on your business constraints:
public class Person
{
public string Logon { get; set; } = "";
public string Badge { get; set; } = "";
public Person(string logon="", string badge="") {}
}
// Use as follow
Person p1 = new Person(logon:"MylogonName");
Person p2 = new Person(badge:"MyBadge");

How about ...
public Person(int personId)
{
this.Load(personId);
}
public Person(string logonName)
{
this.Load(logonName);
}
public Person(Object badgeNumber)
{
//load logic here...
}