No parameterless constructor defined for this object

Question

In my project, I create Linq-to-SQL classes using SqlMetal. The problem with this is that SqlMetal doesn't appear to create a parameterless constructor. I've always gotten around this because I can always get the default connectionstring name and pass it to the constructor - however, now I am being forced to use a LinqDataSource in markup, not code, so I can't specify a constructor.

Is there any way of forcing SQLMetal to generate a parameterless constructor?
Alternatively, flipping it on its head, is there actually a way of specifying a connection string in the markup, like this:

ContextTypeName="MyNameSpace.DAL(defaultconnStr)"

Answer 1

I think you can create a partial class with a new parameterless constructor.

Answer 2

SqlMetal should have generated your Entities class using a partial class. You should be able to simply add a parameterless constructor in another partial class definition:

public partial class WhateverYourEntitiesAreCalledEntities():
    this(defaultConnStr)
{
}