C# Best practices - Set readonly model property value from BLL

Question

Consider the below:

public class Project.Model.ModelName : BaseClass
{
    private int _id;
    private string _name;

    public int ID
    {
        get { return _id; }
        set { _id = value; }
    }

    public string Name
    {
        get { return _name; }
    }
}

public class Project.BLL.ModelName
{
    public static string ComputeName(Model.ModelName m)
    {
        // Determine value using complex business logic

        return "Whatever";
    }

    public static bool SetName(Model.ModelName m)
    {
        string Name = ComputeName(m);

        // How can I set the ModelName.Name value here?
        m.Name = ??? // No set accessor
    }
}

I have a model with a string property that only has a get accessor, we do not want the value to be set directly.

The value for the property is computed in the BLL, a different library.

What's the best way to set the value of the property without using reflection?

For clarification, the challenge is that the Name value needs to be immutable. The same model is frequently accessed and modified. We did not want to risk someone assigning a value to it after the fact. I guess I'm looking for a best practice to maintain immutability.

As it shown now there is absolutely no way to set this `_name` field without reflection. You need to explain what you can/can't change so different options could be suggested. — Alexei Levenkov, Jul 30 '14 at 20:44
You must make that property have a setter. If the BLL needs to modify it, then the model needs to expose it. — Moby Disk, Jul 30 '14 at 20:48
"how to modify immutable value" does not make much sense to me. Consider reading [Kinds of Immutability](http://blogs.msdn.com/b/ericlippert/archive/2007/11/13/immutability-in-c-part-one-kinds-of-immutability.aspx) by Eric Lippert so you can clarify what "immutable" means in your case. — Alexei Levenkov, Jul 30 '14 at 21:55

score 0 · Accepted Answer · answered Jul 30 '14 at 21:02

ModelName.Name property only have a getter specified on _name. There is no way you it can be altered as it is. The only way to do it while preventing the other to do the same is through access modifier.

If Project.BLL and Project.Model is within the same assembly, you can use the internal modifier to restrict the access from other assembly. or apply a [assembly: InternalsVisibleTo("Project.BLL")] on Project.Model.ModelName

 //1. Add a setter on the property, or : 
public string Name
{
    get { return _name; }
    internal set { _name = value; }
}

//2. Add a setter method for _name :
internal void SetName(string value)
{
    _name = value;
}

I ended up using this general solution. The value needed to be immutable after it was initially set.I used a internal set, which allowed the value to be loaded to the Model from the DAL, and an internal void to set the value from the BLL. InternalsVisibleTo for used for both the BLL and DAL libraries. — Stephen, Jul 31 '14 at 14:40

C# Best practices - Set readonly model property value from BLL

1 Answers1