C# – How to use the new Subsonic 3.0 IRepository pattern

asp.netcsubsonic

Can someone (hopefully Rob) explain how to implement the new SubSonicRepository<> Pattern? I have used it with the old version and the MVC templates (in web forms) using the following initialization.

    public IRepository<StaffingPosition> _StaffingPositionsRepository;

    public  StaffingBase()
    {
        _StaffingPositionsRepository = new SubSonicRepository<StaffingPosition>();
    }
    public StaffingBase(IRepository<StaffingPosition> staffingpositionsRepo)
    {
        _StaffingPositionsRepository = staffingpositionsRepo;
    }

Note that my WCF Service inherits this class for ease of access.
Now SubSonicRepository() requires an argument of IQuerySurface and I'm not sure the best way to make this happen. I really dig the IRepository pattern and want to try to stick with it if possible…That is, unless anyone has better ideas. Thanks!

Best Answer

The templates generate a new class that implement IQuerySurface, the name of which you can configure in the main .tt file (usually something like NorthwindDb). Usually all that is needed is to pass a new instance of this class to the repository:

_StaffingPositionsRepository = new SubSonicRepository<StaffingPosition>(new StaffingDB());

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The Activator class within the root System namespace is pretty powerful.

There are a lot of overloads for passing parameters to the constructor and such. Check out the documentation at:

http://msdn.microsoft.com/en-us/library/system.activator.createinstance.aspx

or (new path)

https://docs.microsoft.com/en-us/dotnet/api/system.activator.createinstance

Here are some simple examples:

ObjectType instance = (ObjectType)Activator.CreateInstance(objectType);

ObjectType instance = (ObjectType)Activator.CreateInstance("MyAssembly","MyNamespace.ObjectType");

C# – How to get the index of the current iteration of a foreach loop

Ian Mercer posted a similar solution as this on Phil Haack's blog:

foreach (var item in Model.Select((value, i) => new { i, value }))
{
    var value = item.value;
    var index = item.i;
}

This gets you the item (item.value) and its index (item.i) by using this overload of LINQ's Select:

the second parameter of the function [inside Select] represents the index of the source element.

The new { i, value } is creating a new anonymous object.

Heap allocations can be avoided by using ValueTuple if you're using C# 7.0 or later:

foreach (var item in Model.Select((value, i) => ( value, i )))
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}

You can also eliminate the item. by using automatic destructuring:

<ol>
foreach ((MyType value, Int32 i) in Model.Select((value, i) => ( value, i )))
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C# – How to create a new object instance from a Type

C# – How to get the index of the current iteration of a foreach loop

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