Interface related design question

Question

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.

Vulpes · 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 Paul · Answer

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 ie 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 Paul · Answer

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.

Vulpes · Answer

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 Paul · Answer

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... :-)

Vulpes · Answer

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 Paul · Answer

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 Paul · Answer

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?

Vulpes · Answer

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 Paul · Answer

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 Paul · Answer

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.