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Description
The Linq Function "DefaultIfEmpty" does not work with JetEntityFrameworkProvider. Upon investigation, the reason is that EntityFramework uses "LEFT OUTER JOIN" in the expression, which is not supported in Access.
For Example:
//Attempts to use "LEFT OUTER JOIN" //Will throw Exception "Join Expression not supported" Entity.Table.DefaultIfEmpty(null).FirstOrDefault(e => e.Id = 1)
As a caveat, this is a problem with Access, not JetEntityFrameworkProvider. The workaround I am using is the following extension method:
namespace System.Linq
{
public static class LinqExtensions
{
///
/// Workaround for
/// not working with JetEntity
///
/// First Value, otherwise default()
public static TSource FirstOrEmpty(this IQueryable source, Expressions.Expression> predicate)
{
IQueryable result = source.Where(predicate);
if (result.Count() == 0)
return default(TSource);
return result.First();
}
}
}