Interface related design question

Sumitra Paul

Hi,

I am very week in design and program to interface. I have a task to design few classes. I have some simple interfaces
like below. Sample interfaces.

public interface IParameterValue
    {
        string ParameterName { get; set; }
        string ParameterValu { get; set; }
    }

the above interface is a kind of common interface.

The below interfaces should actually implement the above interface.

Area Parameter interface:

public interface IAreaParameter
    {
        string AreaId { get; set; }
    }

    public class AreaParameter : IAreaParameter
    {
       public string AreaId { get; set; }
    }

Plot paramtere interface:

public interface IPlotParameter
    {
        string AreaId { get; set; }
        string PartId { get; set; }
    }

    public class PlotParameter : IPlotParameter
    {
        public string AreaId { get; set; }
        public string PartId { get; set; }
    }

Now the common interface IParameterValue has ParameterName and ParameterValu.
There will be one more incoming value scope. depending on the scope
the paramterValu will be applied Area wise or Plot wise.

Now, I think we have to implement IParameterValue interface to IAreaParameter and IPlotParamter.
My question is, how to implement in code and if we implement how to access all this paramters
from other class and assign a value to them.

Simple question i think but did'n work with interfaces more so...

Thanks.

11 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes13y ago
Accepted answer
I thought I'd just spend a few minutes seeing how the design would look if we get rid of the IParameterValue interface as you don't really need that and the abstract class as well:

using System;
using System.Collections;
using System.Collections.Generic;

class Parameters
{
public string Scope { get; set; }
public string AreaId { get; set; }
public string PartId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}

public interface IAreaParameter
{
string AreaId { get; set; }
}

public interface IPlotParameter
{
string AreaId { get; set; }
string PartId { get; set; }
}

public abstract class AbstractParamterValue
{
public abstract string ParameterName { get; set; }
public abstract string ParameterValu { get; set; }
}

public class AreaParameter : AbstractParamterValue, IAreaParameter
{
public string AreaId { get; set; }
public override string ParameterName { get; set; }
public override string ParameterValu { get; set; }
}

public class PlotParameter : AbstractParamterValue, IPlotParameter
{
public string AreaId { get; set; }
public string PartId { get; set; }
public override string ParameterName { get; set; }
public override string ParameterValu { get; set; }
}

public interface IUser
{
string Scope{get;set;}
IEnumerable ParametersValues{get;set;}
}

public class User : IUser
{
public string Scope { get; set; }
public IEnumerable ParametersValues { get; set; }
}

class Program
{
static void Main(string[] args)
{
user = new User();
var parameters = GetParameters();
IEnumerable paramterValues = AssignValues(parameters);
foreach(AbstractParamterValue apv in paramterValues)
{
Console.WriteLine(apv.GetType());

if (apv is IAreaParameter)
{
Console.WriteLine(((IAreaParameter)apv).AreaId);
}
else if (apv is IPlotParameter)
{
Console.WriteLine(((IPlotParameter)apv).AreaId);
Console.WriteLine(((IPlotParameter)apv).PartId);
}
Console.WriteLine(apv.ParameterName);
Console.WriteLine(apv.ParameterValu);

Console.WriteLine();
}

Console.ReadKey();
}

private static IUser user;

private static IEnumerable AssignValues(IEnumerable perameters)
{
IList parameterValueList = new List();
foreach (Parameters p in perameters)
{
if (p.Scope == "Plot")
{
user.Scope = p.Scope;
IPlotParameter plotParameter = new PlotParameter();
plotParameter.AreaId = p.AreaId;
plotParameter.PartId = p.PartId;
AbstractParamterValue parammeterValue = (AbstractParamterValue)plotParameter;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
if (p.Scope == "Area")
{
user.Scope = p.Scope;
IAreaParameter areaParam = new AreaParameter();
areaParam.AreaId = p.AreaId;
AbstractParamterValue parammeterValue = (AbstractParamterValue)areaParam;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
}
return parameterValueList;
}

private static IEnumerable GetParameters()
{
// Sample values collection created.
// realtime, this values will be a collection coming from outside.

Parameters obj1 = new Parameters
{
Scope = "Plot",
AreaId = "A1",
PartId = "L1Value",
ParameterName = "ParameterA",
ParameterValu = "ParameterVal"
};

Parameters obj2 = new Parameters
{
Scope = "Area",
AreaId = "A2",
PartId = "A2Part",
ParameterName = "ParameterB",
ParameterValu = "ParameterValue"
};

Parameters obj3 = new Parameters
{
Scope = "Plot",
AreaId = "A3",
PartId = "A3Part",
ParameterName = "ParameterC",
ParameterValu = "ParameterValue"
};

IEnumerable param = new List { obj1, obj2, obj3 };
return param;
}
}

The output is once again the same as before.
Sumitra Paul13y ago
Hi Vulpes,

There is again some problem with this design as I thought the requirement in a wrong way.
Actually, I was considering IParameterValue as top in my inheritence hirarchy.
Like I was thinking there will be a parameter value and I have to look into which AreaId and PartId it belongs to.

But actually, It seems I have to first consider the AreaId or PartId and assign all the parameters belonging to each AreaId or PartId i.e a Area can contain multiple parameterValues and if Area does not contain Parameters then
it might contain multiple Plots/Part which will contain multiple parameters.

I have added one more interface which "IGroupOfAllArea". This can also contain parameterValues. The thing is that if "IGroupOfAllArea" has Parameter then I will add the IParameterValue with a scope as "AllArea" and
if IArea has parameter then I will add the IParameterValue with a scope as "Area" and
if IPlot has parameter then I will add the IParameterValue with a scope as "Plot".

Let me explain it in other way.

Sample interfaces without any design.

public interface IParameterValue
{
string ParameterName { get; set; }
string ParameterValu { get; set; }
}

public interface IGroupOfAllArea
{
IEnumerable ParameterValues { get; set; }
IEnumerable Areas { get; set; }
}

public interface IArea
{
string AreaId { get; set; }
IEnumerable ParameterValues { get; set; }
IEnumerable Plots { get; set; }
}

public interface IPlot
{
string PlotId { get; set; }
IEnumerable ParameterValues {get;set;}
}

public interface IUser
    {
        // Earlier I was returning IParameterValue, But now not sure what should I return
        // to the user which will make easy to manupulate my return collection.
        //IEnumerable ParametersValues { get; set; }
    }

Now, while assigning the values to my return IEnumerable collection I will be
checking following things:

1.I will be actually checking first the "IGroupOfAllArea" and if "ParameterValues" contains
values, I will add scope as "AllArea" and add the parameter to my list.
2. then I will iterate through "Areas" collection of "IGroupOfAllArea" and get all the "ParameterValues" for each "AreaId" respectively and add to my list with Scope as "Area".
SO here for each AreaId, I might have multiple parameterValues.
Now the same way
3. I will iterate through "Plots" collection and get all the "parameterValues" for each Plot respectively and add it to my collection with scope as "Plot".

for the above requirement, the interface hyrarchy that we had earlier is not going to work i.e
we were implementing IParameter value to IAreaParameter and IPlotParameter.

Note: All this values i,e Parameter values, Area Id's and parameters coresponsding to this Ids etc will be available in a in coming collection. I just need to design my interfaces and assign the values. We will be manupulating our collection and sending it back again using a kind of adaptor pattern.

I could have written some sample code, but as I am not atall sure about the interface design only, could'n write that. Also, now I am not sure like whether I should return IParameterValue list to the user or I have to retrun I list of IGroupOfAllArea? Because the concern is that the we should not have much dificulty menupulating the collection later.

If posible can you tell me how I can design this ?
Sorry for unmarking the answer.

Thanks a lot.
Sumitra Paul13y ago
Thanks vulpes..I have few more questions on upcasting and downcasting..but better I should ask in new thread.

I will implement this and see how it goes.
Thanks again.
Vulpes13y ago
OK, I've adjusted the design so that AreaParameter and PlotParameter both now inherit from an abstract base class and indirectly implement IParameterValue via that.

You could in fact get rid of the IParameterValue interface altogether (unless you might want to implement it via some other base class) and just use the abstract class in the design but, as you haven't asked for that, I've left it as it is for now:

using System;
using System.Collections;
using System.Collections.Generic;

class Parameters
{
public string Scope { get; set; }
public string AreaId { get; set; }
public string PartId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}

public interface IParameterValue
{
string ParameterName { get; set; }
string ParameterValu { get; set; }
}

public interface IAreaParameter
{
string AreaId { get; set; }
}

public interface IPlotParameter
{
string AreaId { get; set; }
string PartId { get; set; }
}

public abstract class AbstractParamterValue : IParameterValue
{
public abstract string ParameterName { get; set; }
public abstract string ParameterValu { get; set; }
}

public class AreaParameter : AbstractParamterValue, IAreaParameter
{
public string AreaId { get; set; }
public override string ParameterName { get; set; }
public override string ParameterValu { get; set; }
}

public class PlotParameter : AbstractParamterValue, IPlotParameter
{
public string AreaId { get; set; }
public string PartId { get; set; }
public override string ParameterName { get; set; }
public override string ParameterValu { get; set; }
}

public interface IUser
{
string Scope{get;set;}
IEnumerable ParametersValues{get;set;}
}

public class User : IUser
{
public string Scope { get; set; }
public IEnumerable ParametersValues { get; set; }
}

class Program
{
static void Main(string[] args)
{
user = new User();
var parameters = GetParameters();
IEnumerable paramterValues = AssignValues(parameters);
foreach(IParameterValue ipv in paramterValues)
{
Console.WriteLine(ipv.GetType());

if (ipv is IAreaParameter)
{
Console.WriteLine(((IAreaParameter)ipv).AreaId);
}
else if (ipv is IPlotParameter)
{
Console.WriteLine(((IPlotParameter)ipv).AreaId);
Console.WriteLine(((IPlotParameter)ipv).PartId);
}
Console.WriteLine(ipv.ParameterName);
Console.WriteLine(ipv.ParameterValu);

Console.WriteLine();
}

Console.ReadKey();
}

private static IUser user;

private static IEnumerable AssignValues(IEnumerable perameters)
{
IList parameterValueList = new List();
foreach (Parameters p in perameters)
{
if (p.Scope == "Plot")
{
user.Scope = p.Scope;
IPlotParameter plotParameter = new PlotParameter();
plotParameter.AreaId = p.AreaId;
plotParameter.PartId = p.PartId;
IParameterValue parammeterValue = (IParameterValue)plotParameter;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
if (p.Scope == "Area")
{
user.Scope = p.Scope;
IAreaParameter areaParam = new AreaParameter();
areaParam.AreaId = p.AreaId;
IParameterValue parammeterValue = (IParameterValue)areaParam;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
}
return parameterValueList;
}

private static IEnumerable GetParameters()
{
// Sample values collection created.
// realtime, this values will be a collection coming from outside.

Parameters obj1 = new Parameters
{
Scope = "Plot",
AreaId = "A1",
PartId = "L1Value",
ParameterName = "ParameterA",
ParameterValu = "ParameterVal"
};

Parameters obj2 = new Parameters
{
Scope = "Area",
AreaId = "A2",
PartId = "A2Part",
ParameterName = "ParameterB",
ParameterValu = "ParameterValue"
};

Parameters obj3 = new Parameters
{
Scope = "Plot",
AreaId = "A3",
PartId = "A3Part",
ParameterName = "ParameterC",
ParameterValu = "ParameterValue"
};

IEnumerable param = new List { obj1, obj2, obj3 };
return param;
}
}

The output, as expected, is the same as before.
Sumitra Paul13y ago
Thanks Vulpes..i was following this post for last 6 hours continuesly :-) Thanks for replying.

Yah, second part of my question..i do belive I can make abstract class say AbstractParameterValue by implementing IParameterValue interface. But not sure how this class will fit in my design?? and how to use it ??

Thanks for replying again... :-)
Vulpes13y ago
On the first point, I added some code to your Main() method to make sure that the design was creating the appropriate kind of object (according to scope) and populating its properties:

static void Main(string[] args)
{
user = new User();
var parameters = GetParameters();
IEnumerable paramterValues = AssignValues(parameters);

foreach(IParameterValue ipv in paramterValues)
{
Console.WriteLine(ipv.GetType());

if (ipv is IAreaParameter)
{
Console.WriteLine(((IAreaParameter)ipv).AreaId);
}
else if (ipv is IPlotParameter)
{
Console.WriteLine(((IPlotParameter)ipv).AreaId);
Console.WriteLine(((IPlotParameter)ipv).PartId);
}
Console.WriteLine(ipv.ParameterName);
Console.WriteLine(ipv.ParameterValu);

Console.WriteLine();
}

Console.ReadKey();
}

The output was as follows from which it can be seen that the design is working fine:

PlotParameter
A1
L1Value
ParameterA
ParameterVal

AreaParameter
A2
ParameterB
ParameterValue

PlotParameter
A3
A3Part
ParameterC
ParameterValue

It's slightly awkward having to cast to IAreaParameter or IPlotParameter to get at the properties which they provide but this can't be helped as IParameterValue doesn't provide these properties.

The only improvement I'd suggest is to pass the IUser object as a second parameter to the AssignValues method, rather than reading it in from a field of the containing class, as this will make the method self-contained and make it easier to pass different IUser objects to it.

I'll reply to the second point in a separate post after I've figured out how to do it.
Sumitra Paul13y ago
Hi Vulpes,
I think i can create an abstract class something like "AbstractParamterValue" and implement IParameterValue as this interface properties are common for
interface IAreaParameter and IPlotParameter.
But how to do that ??

Can you put some light on the design ??
Thanks again..
Sumitra Paul13y ago
Hi Vulpes,

Thanks a lot for the reply. I have done some changes to the class design.
I think with the below program you can actually understand what I am going to design.

Can you please tell me if the design is correct? or there can be some other best way to do the same thing.
I might have one more interface same as IAreaParameter.

Code sample:

// Sample class. this class is created just to create an object with
// these values. realtime, this values will be a collection coming from outside.
class Parameters
{
public string Scope { get; set; }
public string AreaId { get; set; }
public string PartId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}
public interface IParameterValue
{
string ParameterName { get; set; }
string ParameterValu { get; set; }
}
public interface IAreaParameter
{
string AreaId { get; set; }
}
public interface IPlotParameter
{
string AreaId { get; set; }
string PartId { get; set; }
}
public class AreaParameter : IAreaParameter, IParameterValue
{
public string AreaId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}
public class PlotParameter : IPlotParameter, IParameterValue
{
public string AreaId { get; set; }
public string PartId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}
public interface IUser
{
string Scope{get;set;}
IEnumerable ParametersValues{get;set;}
}
public class User : IUser
{
public string Scope { get; set; }
public IEnumerable ParametersValues { get; set; }
}

class Program
{
static void Main(string[] args)
{
user = new User();
var parameters = GetParameters();
IEnumerable paramterValues = AssignValues(parameters);
Console.ReadKey();
}
private static IUser user;
private static IEnumerable AssignValues(IEnumerable perameters)
{
IList parameterValueList = new List();
foreach (Parameters p in perameters)
{
if (p.Scope == "Plot")
{
user.Scope = p.Scope;
IPlotParameter plotParameter = new PlotParameter();
plotParameter.AreaId = p.AreaId;
plotParameter.PartId = p.PartId;
IParameterValue parammeterValue = (IParameterValue)plotParameter;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
if (p.Scope == "Area")
{
user.Scope = p.Scope;
IAreaParameter areaParam = new AreaParameter();
areaParam.AreaId = p.AreaId;
IParameterValue parammeterValue = (IParameterValue)areaParam;
parammeterValue.ParameterName = p.ParameterName;
parammeterValue.ParameterValu = p.ParameterValu;
parameterValueList.Add(parammeterValue);
}
}
return parameterValueList;
}
private static IEnumerable GetParameters()
         {
             // Sample values collection created.
             // realtime, this values will be a collection coming from outside.

            Parameters obj1 = new Parameters
             {
                 Scope = "Plot",
                 AreaId = "A1",
                 PartId = "L1Value",
                 ParameterName = "ParameterA",
                 ParameterValu = "ParameterVal"
             };

            Parameters obj2 = new Parameters
             {
                 Scope = "Area",
                 AreaId = "A2",
                 PartId = "A2Part",
                 ParameterName = "ParameterB",
                 ParameterValu = "ParameterValue"
             };

            Parameters obj3 = new Parameters
             {
                 Scope = "Plot",
                 AreaId = "A3",
                 PartId = "A3Part",
                 ParameterName = "ParameterC",
                 ParameterValu = "ParameterValue"
             };

            IEnumerable param = new List { obj1, obj2, obj3 };
             return param;
         }
}

can you please tell me if the design is correct?
Vulpes13y ago
No, you don't need to implement IParameterValue using a separate class because a class in C# can implement multiple interfaces even though it can only inherit from a single base class.

Here's how you can assign values to the properties via interface references and also read them back. I've used object references for the latter because you can access all properties using the same reference. However, you can still use interface references for reading back except that each interface can only access its own properties.

The values I've assigned are purely for illustration and nonsense in themselves:

using System;

public interface IParameterValue
{
string ParameterName { get; set; }
string ParameterValu { get; set; }
}

public interface IAreaParameter
{
string AreaId { get; set; }
}

public interface IPlotParameter
{
string AreaId { get; set; }
string PartId { get; set; }
}

public class AreaParameter : IAreaParameter, IParameterValue
{
public string AreaId { get; set; }
public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}

public class PlotParameter : IPlotParameter, IParameterValue
{
public string AreaId { get; set; }
public string PartId { get; set; }

public string ParameterName { get; set; }
public string ParameterValu { get; set; }
}

class User
{
static void Main()
{
// set properties through interface variables
IAreaParameter iap = new AreaParameter();
iap.AreaId = "AB";
IParameterValue ipv = (IParameterValue)iap; // get reference to same object
ipv.ParameterName = "Scope";
ipv.ParameterValu = "Local";

IPlotParameter ipp = new PlotParameter();
ipp.AreaId = "CD";
ipp.PartId = "123";
IParameterValue ipv2 = (IParameterValue)ipp; // get reference to same object
ipv2.ParameterName = "Scope";
ipv2.ParameterValu = "External";

// now access them through object variables
AreaParameter ap = (AreaParameter)iap;
Console.WriteLine("Property values for AreaParameter object");
Console.WriteLine(" Area Id : {0}", ap.AreaId);
Console.WriteLine(" Parameter Name : {0}", ap.ParameterName);
Console.WriteLine(" Parameter Value : {0}", ap.ParameterValu);
Console.WriteLine();
PlotParameter pp = (PlotParameter)ipp;
Console.WriteLine("Property values for PlotParameter object");
Console.WriteLine(" Area Id : {0}", pp.AreaId);
Console.WriteLine(" Part Id : {0}", pp.PartId);
Console.WriteLine(" Parameter Name : {0}", pp.ParameterName);
Console.WriteLine(" Parameter Value : {0}", pp.ParameterValu);
Console.ReadKey();
}
}

The output should be:

Property values for AreaParameter object
Area Id : AB
Parameter Name : Scope
Parameter Value : Local

Property values for PlotParameter object
Area Id : CD
Part Id : 123
Parameter Name : Scope
Parameter Value : External
Sumitra Paul13y ago
Let me clarify my question in other way.
I know how to implement an interface.
My question is design related and also if we implement the interface like below, how to
access it and assign values to all the properties and also read them.
Say, Interface is implemented like this:
public interface IParameterValue
    {
        string ParameterName { get; set; }
        string ParameterValu { get; set; }
    }

public interface IAreaParameter
    {
        string AreaId { get; set; }
    }
public interface IPlotParameter
    {
        string AreaId { get; set; }
        string PartId { get; set; }
    }

Implementaion:
public class AreaParameter : IAreaParameter, IParameterValue
    {
       public string AreaId { get; set; }
       public string ParameterName { get; set; }
       public string ParameterValu { get; set; }
    }
public class PlotParameter : IPlotParameter, IParameterValue
    {
        public string AreaId { get; set; }
        public string PartId { get; set; }
        public string ParameterName { get; set; }
        public string ParameterValu { get; set; }

    }

Do I need to implement IParameterValue interface in a saparate class ParameterValue??
How to assign or access a value to these fields from other class say a class "USER"?
Actually, i don'nt know how to code this for assigning and retriving values ?
Thanks.
Sumitra Paul13y ago
Let me clarify my question in other way.
I know how to implement an interface.
My question is design related and also if we implement the interface like below, how to
access it and assign values to all the properties and also read them.
Say, Interface is implemented like this:
public interface IParameterValue
    {
        string ParameterName { get; set; }
        string ParameterValu { get; set; }
    }

public interface IAreaParameter
    {
        string AreaId { get; set; }
    }
public interface IPlotParameter
    {
        string AreaId { get; set; }
        string PartId { get; set; }
    }

Implementaion:
public class AreaParameter : IAreaParameter, IParameterValue
    {
       public string AreaId { get; set; }
       public string ParameterName { get; set; }
       public string ParameterValu { get; set; }
    }
public class PlotParameter : IPlotParameter, IParameterValue
    {
        public string AreaId { get; set; }
        public string PartId { get; set; }
        public string ParameterName { get; set; }
        public string ParameterValu { get; set; }

    }

Do I need to implement IParameterValue interface in a saparate class ParameterValue??
How to assign or access a value to these fields from other class say a class "USER"?
Actually, i don'nt know how to code this for assigning and retriving values ?
Thanks.