Dynamicky generujte výraz lambda s konstantami z proměnných

To lze provést poměrně snadno pomocí ExpressionVisitor který vyhodnotí ConstantExpression takto:

public static class ExpressionUtils
{
    public static Expression<TDelegate> ReplaceVariablesWithConstants<TDelegate>(this Expression<TDelegate> source)
    {
        return source.Update(
            new ReplaceVariablesWithConstantsVisitor().Visit(source.Body), 
            source.Parameters);
    }

    class ReplaceVariablesWithConstantsVisitor : ExpressionVisitor
    {
        protected override Expression VisitMember(MemberExpression node)
        {
            var expression = Visit(node.Expression);
            if (expression is ConstantExpression)
            {
                var variable = ((ConstantExpression)expression).Value;
                var value = node.Member is FieldInfo ?
                    ((FieldInfo)node.Member).GetValue(variable) :
                    ((PropertyInfo)node.Member).GetValue(variable);
                return Expression.Constant(value, node.Type);
            }
            return node.Update(expression);
        }
    }
}