Generic method extraction

Question

I am writing mock of DbSets and ended up writing series of code like this.

int rowCount = 0;
var maxOrderId = EntityContainer.Set<Order>().Max(a => a.Id);
var newOrders = EntityContainer.Set<Order>().Where(a =>a.Id == 0);
foreach (var order in newOrders)
{
    order.Id = ++maxOrderId;
    rowCount++;
}

var maxServiceId = EntityContainer.Set<Service>().Max(a => a.Id);
var newServices = EntityContainer.Set<Service>().Where(a => a.Id == 0);
foreach (var service in newServices)
{
    service.Id = ++maxServiceId;
    rowCount++;
}

There are more entities though in this list. Is there a way I can extract these to a generic method? Something like:

int GenerateID<Order>();

I tried using dynamic, but that compiler complains that dynamics are not allowed in lambda expressions.

Maybe not relevant to you case, but have you checked https://github.com/tamasflamich/effort before rolling out your own implementation? — Kaspars Ozols, Mar 27 '17 at 06:39

g t · Accepted Answer · 2017-03-27T07:45:46.770

1

You would have to ensure your objects implement an interface like:

interface IItem
{
    int Id { get; set; }
}

The GenerateId method would then look like this:

int GenerateID<T>(int rowCount) where T : IItem
{
    var maxId = EntityContainer.Set<T>().Max(a => a.Id);
    var newItems = EntityContainer.Set<T>().Where(a => a.Id == 0);
    foreach (T item in newItems)
    {
        item.Id = ++maxId;
        rowCount++;
    }

    return rowCount;
}

Edit

To avoid having to add interfaces, you could pass accessor function/actions:

int GenerateId<T>(int rowCount, Func<T, int> getIdFunc, Action<T, int> setIdFunc)
    where T : class 
{
    var maxId = EntityContainer.Set<T>().Max(getIdFunc);
    var newItems = EntityContainer.Set<T>().Where(a => getIdFunc.Invoke(a) == 0);
    foreach (T item in newItems)
    {
        setIdFunc.Invoke(item, maxId++);
        rowCount++;
    }

    return rowCount;
}

Then call as:

rowCount = GenerateId<Order>(rowCount, o => o.Id, (o, id) => o.Id = id);
rowCount = GenerateId<Service>(rowCount, o => o.Id, (o, id) => o.Id = id);

edited Mar 27 '17 at 07:45

answered Mar 27 '17 at 06:34

g t

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a.Id wouldnt be a valid member unless we use a Contraint of Class/Interface that has member as Id – Raghav Mar 27 '17 at 06:36
It would not work because nothing says that `T` has an `Id`. `T` must be of some interface then. – Kaspars Ozols Mar 27 '17 at 06:36
does that mean, i have to extend all my classes with the IItem Interface?? – Raghav Mar 27 '17 at 06:37
I am expecting some reflection based techniques to help me out... I suck at reflection.. – Raghav Mar 27 '17 at 06:39

score 0 · Answer 2 · edited May 23 '17 at 12:17

If I understand right you need autoincrement Id for your model.

Please see this answer

Additionally if you want to set started id just use smth like this

public class Model
{
    private static int m_Counter = 0;
    //
    public static ResetCounter(int start)
    {
        m_Counter=start;
    }
    public int Id { get; set; }

    public Model()
    {
        this.Id = System.Threading.Interlocked.Increment(ref m_Counter);
    }
}

and using

Model.ResetCounter(maxServiceId)//optionally 
new Model {} //now When you create new object Model.Id should increment by itself

Generic method extraction

2 Answers2