Linq Expression in Case Statement

I'm using LINQ with Expression trees and a case Statement in my Select. I'm doing this because the Where Condition is build dynamicly and in my Result, I need to know, which part of the where was true.

This works fine:

        ParameterExpression peTbl = Expression.Parameter(typeof(MyTbl), "mytbl");

        Expression left = Expression.Property(peTbl, "Col1");
        Expression right = Expression.Constant((ulong)3344, typeof(ulong));
        Expression e1 = Expression.Equal(left, right);

        left = Expression.Property(peTbl, "Col2");
        right = Expression.Constant((ulong)27, typeof(ulong));
        Expression e2 = Expression.Equal(left, right);

        Expression predicateBody = Expression.Or(e1, e2);

        Expression<Func<MyTbl, bool>> whereCondition = Expression.Lambda<Func<MyTbl, bool>>(predicateBody, new ParameterExpression[] { peTbl });

        var query = myTbl
                    .Where(whereCondition)
                    .Select(s => new { mytbl = s, mycase = (s.Col1 == 3344 ? 1 : 0) });

But now, I want to use the Expression e1 in my case Statement.

Something like this:

            var query = myTbl
                    .Where(whereCondition)
                    .Select(s => new { mytbl = s, mycase = (e1 == true ? 1 : 0) });

Any idea how to do this?

via Chebli Mohamed