Refactoring a method for specific clients

Question

Methods specific for customers:

I try to refactore a code, where are a lot of logic for specifi customer:

public void SendDocumentsToCustomer(List<Case> cases)
{
    foreach(var case in cases)
    {
        if(case.CustomerId==123)
        {
        if(case.Type==1 || case.Type==2)
        {
        SendDocumentsToCustomer123(case)
        }
        else if(case.CustomerId==456)
        {
        if(case.Type==1 || case.Type==3)
        {
        SendDocumentsToCustomer456(case);
        }
        }
        else if(case.CustomerId==768)
        {
        if(case.Type==2)
        {
        SendDocumentsToCustomer456(case);
        }
        else
        {
        SendDocumentsToCustomer(case);
        }
    }
}

The list of specific customer will grow, and the conditions will be modified as well. I will have a generic solution, but maybe code like this with method DoItForClient123 is not a bad solution and I should leave it like that and goint this way introduce methods like CanDocumentsBeSendToClient123 and so on?

I will be very gratefull for some input

Answer 1

To separate logic for each specific customer I would use such code:

abstract class DocumentSender   //Base class for all document sending components
{
    public abstract bool CanSend(Case @case);        // Check if sender can send the document
    public abstract void SendDocument(Case @case);   // Send the document
}

class DefaultDocumentSender : DocumentSender
{
    public override bool CanSend(Case @case)
    {
        return true;   //Can process all requests
    }

    public override void SendDocument(Case @case)
    {
       // Do something
    }
}

class Customer123DocumentSender : DocumentSender
{
    public override bool CanSend(Case @case)
    {
        return @case.CustomerId == 123;   //Specific case
    }

    public override void SendDocument(Case @case)
    {
        if(@case.Type==1 || @case.Type==2)
        {
            // Do something different
        }
    }
}

//Separate class for getting the correct sender
class CaseSenderFactory    
{
    readonly List<DocumentSender> _senders = new List<DocumentSender>();

    public DocumentSenderFactory()
    {
        //Initialize the list of senders from the most specific. 
        _senders.Add(new Customer123DocumentSender());
        // Add more specific cases here
        _senders.Add(new DefaultDocumentSender());   //Last item should be the default sender
    }

    public DocumentSender GetDocumentSender(Case @case)
    {
        //At least one sender needs to satisfy the condition
        return _senders.First(x => x.CanSend(@case));   
    }
}

You then can use the senders like this:

var factory = new DocumentSenderFactory();
foreach(var @case in cases)
{
    var sender = factory.GetDocumentSender(@case);
    sender.SendDocument(@case);
}