Hi,
No generator, but try this:
public static IQueryable<TSource> Between<TSource, TKey>(this
IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector,
TKey low, TKey high) where TKey : IComparable<TKey>
{
// Get a ParameterExpression node of the TSource that is used in the
expression tree
var sourceParameter = Expression.Parameter(typeof(TSource));
// Get the body and parameter of the lambda expression
var body = keySelector.Body;
ParameterExpression parameter = null;
if (keySelector.Parameters.Count > 0)
{
parameter = keySelector.Parameters[0];
}
// Get the Compare method of the type of the return value
var compareMethod = typeof(TKey).GetMethod("CompareTo", new Type[] {
typeof(TKey) });
var zero = Expression.Constant(0, typeof(Int32));
// Expression.LessThanOrEqual and Expression.GreaterThanOrEqual method are
only used in
// the numeric comparision. If we want to compare the non-numeric type, we
can't directly
// use the two methods.
// So we first use the Compare method to compare the objects, and the
Compare method
// will return a int number. Then we can use the LessThanOrEqual and
GreaterThanOrEqua method.
// For this reason, we ask all the TKey type implement the IComparable<>
interface.
var upper = Expression.LessThanOrEqual(Expression.Call(body, compareMethod,
Expression.Constant(high)), zero);
var lower = Expression.GreaterThanOrEqual(Expression.Call(body,
compareMethod, Expression.Constant(low)), zero);
var andExpression = Expression.AndAlso(upper, lower);
// Get the Where method expression.
var whereCallExpression = Expression.Call
(
typeof(Queryable),
"Where",
new Type[] { source.ElementType },
source.Expression,
Expression.Lambda<Func<TSource, Boolean>>(andExpression, new
ParameterExpression[] { parameter })
);
return (source.Provider.CreateQuery<TSource>(whereCallExpression));
}
On Wednesday, October 21, 2015 at 3:58:45 PM UTC+1, Jeffrey Becker wrote:
>
> I'm having issues when trying to define an 'IsBetween' extension method
> per the attached files. NHibernate ends up throwing the following error
> and I'm at a loss about it:
>
>
> NHibernate.Hql.Ast.ANTLR.QuerySyntaxExceptionA recognition error occurred.
> [.Where[GpisReplacement.Domain.Event](NHibernate.Linq.NhQueryable`1[GpisReplacement.Domain.Event],
>
> Quote((x, ) => (.IsBetween(x.FromDate, p1, p2, ))), )]
> at NHibernate.Hql.Ast.ANTLR.ErrorCounter.ThrowQueryException()
> at NHibernate.Hql.Ast.ANTLR.HqlSqlTranslator.Translate()
> at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.DoCompile(IDictionary`2
> replacements, Boolean shallow, String collectionRole)
> at
> NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(IASTNode
>
> ast, String queryIdentifier, String collectionRole, Boolean shallow,
> IDictionary`2 filters, ISessionFactoryImplementor factory)
> at
> NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(IQueryExpression
> queryExpression, Boolean shallow, IDictionary`2 enabledFilters)
> at NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(IQueryExpression
> queryExpression, Boolean shallow)
> at NHibernate.Impl.AbstractSessionImpl.CreateQuery(IQueryExpression
> queryExpression)
> at NHibernate.Linq.DefaultQueryProvider.PrepareQuery(Expression
> expression, ref IQuery query, ref NhLinqExpression nhQuery)
> at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression)
> at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression)
> at Remotion.Linq.QueryableBase`1.GetEnumerator()
> at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
> at System.Linq.Enumerable.ToList(IEnumerable`1 source)
> at GpisReplacement.Test.TestBetween.CanBetween() in TestBetween.cs:
> line 25
>
>
> The other two extension methods come off without a hitch.
>
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