Compositional Patterns: Policies

DefaultPolicy.cs

public class DefaultPolicy : IPolicy
{
    public bool Matches()
    {
        return true;
    }
    
    public void Execute()
    {
        // default behavior
    }
}

IPolicy.cs

public interface IPolicy
{
    bool Matches();
    void Execute();
}

PolicyConsumer.cs

public class PolicyConsumer
{
    private readonly IEnumerable<IPolicy> _policies;
    
    public PolicyConsumer(IEnumerable<IPolicy> policies)
    {
        var configuredPolicies = new List<IPolicy>();
        configuredPolicies.AddRange(policies);
        configuredPolicies.Add(new DefaultPolicy()); // make sure this is last
		
        _policies = configuredPolicies;
    }
	
    public void Execute()
    {
        var policy = _policies
                .FirstOrDefault(p => p.Matches());
        if(policy == null)
        {
            // throw, log, etc.
            return;
        }
		
        policy.Execute();
    }
}