Question

i’m starter in Repository Pattern in EntityFreamework in Bussiness Layer

i Have Get Methods

public IQueryable<Contract> GetAll()
{
    var repository = new ContractsRepository(this.Context);
    return repository.GetAll();
}

public IQueryable<Contract> GetAll(Func<Contract, bool> predicate)
{
    var repository = new ContractsRepository(this.Context);
    return repository.GetAll(predicate);
}

These are good,But I want to do computing on the field when a function return value to do what?

For example, I have 2 tables Table 1 and Table 2

• Table1 have a Field1 and Field 2
• Table2 have Field3 and Field4.

I want the Bussiness layer Table1 Get method to write the following

Field1 ,Field2,Field1+Field3,Field2+Field4

thanks

Answer 1

I disagree with Tony Hopkinson’s comment. You should not add a read-only property to your Contact class, because such a property cannot be used in LINQ to Entities, and hence aren’t suitable for methods which return IQueryable.

Instead, do something like:

    public IQueryable<ContractSumsModel> GetSums()
    {
        var repository = new ContractsRepository(this.Context);
        return from c in repository.GetAll()
               select new ContractSumsModel
               {
                   Field1 = c.Field1,
                   Field2 = c.Field2,
                   Fields1and3 = Field1 + Field3,
                   Fields2and4 = Field2 + Field4
               };
    }

The nice thing about this is that you can further compose the query:

var q = MyBusinessLayer.GetSums().OrderBy(c => c.Fields1and3).Take(5);

…and the whole thing is done in SQL.