LINQ2SQL, Persistence Ignorance and Domain Models

Question

Has anyone here have used LINQ to SQL to support the persistence of domain models?

I'm not planning to use the LINQ2SQL entity designer, just plain-old hand-coded XML mapping and I'm currently having roadblocks.

I'm attempting to use it in a DDD example I'm doing, since my audience only knows LINQ2SQL.

Answer 1

POCOs can be mapped so it can be used with a DataContext.

However, I find the mapping a bit leaky. Data model information is now leaking to the domain entity. Consider this example:

    <Table Name="dbo.products">
    <Type Name="Ptc.Store.Core.Product">
        <Column Name="id" Member="Id" IsDbGenerated="true" IsPrimaryKey="true" CanBeNull="false" DbType="INT NOT NULL IDENTITY" />
        <Column Name="name" Member="Name" CanBeNull="false"  DbType="VARCHAR(50) NOT NULL" />
    </Type>
</Table>

<Table Name="[dbo].branches">
    <Type Name="Ptc.Store.Core.Branch">
        <Column Name="id" Member="Id" IsDbGenerated="true" IsPrimaryKey="true" DbType="INT NOT NULL IDENTITY" />
        <Column Name="name" Member="Name" CanBeNull="false" DbType="VARCHAR(50) NOT NULL" />
    </Type>
</Table>

<Table Name="[dbo].sales">
    <Type Name="Ptc.Store.Core.Sale">
        <Column Name="id" Member="Id" IsDbGenerated="true" IsPrimaryKey="true" CanBeNull="false" DbType="INT NOT NULL IDENTITY" />
        <Column Name="transaction_date" Member="TransactionDate" CanBeNull="false" DbType="DATETIME" />
        <Column Name="amount" Member="Amount" CanBeNull="false" DbType="MONEY" />
        <Association Name="sales_item" Member="Item" IsForeignKey="true" ThisKey="ProductId" OtherKey="Id"  />
        <Association Name="sales_location" Member="Location" IsForeignKey="true" ThisKey="BranchId" OtherKey="Id" />

        <!-- Why do I have to map foreign keys? Looks leaky to me.-->
        <Column Name="product_id" Member="ProductId" CanBeNull="false" DbType="INT" />
        <Column Name="branch_id" Member="BranchId" CanBeNull="false" DbType="INT" />
    </Type>
</Table>

The worse part is that I have to explicitly declare properties on my entities to match the data model's foreign keys. I didn't have to do this with NHibernate.

Is there any better way to do this without explicitly writing properties and their mapping to the data model?