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JoinBuilder.cs
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JoinBuilder.cs
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using System.Collections.Generic;
using System.Linq.Expressions;
using NHibernate.Linq.Clauses;
using Remotion.Linq;
using Remotion.Linq.Clauses;
using Remotion.Linq.Clauses.Expressions;
using Remotion.Linq.Parsing;
namespace NHibernate.Linq.Visitors
{
public interface IJoiner
{
Expression AddJoin(Expression expression, string key);
bool CanAddJoin(Expression expression);
void MakeInnerIfJoined(string key);
}
public class Joiner : IJoiner
{
private readonly Dictionary<string, NhJoinClause> _joins = new Dictionary<string, NhJoinClause>();
private readonly NameGenerator _nameGenerator;
private readonly QueryModel _queryModel;
internal Joiner(QueryModel queryModel)
{
_nameGenerator = new NameGenerator(queryModel);
_queryModel = queryModel;
}
public IEnumerable<NhJoinClause> Joins
{
get { return _joins.Values; }
}
public Expression AddJoin(Expression expression, string key)
{
NhJoinClause join;
if (!_joins.TryGetValue(key, out join))
{
join = new NhJoinClause(_nameGenerator.GetNewName(), expression.Type, expression);
_queryModel.BodyClauses.Add(join);
_joins.Add(key, join);
}
return new QuerySourceReferenceExpression(@join);
}
public void MakeInnerIfJoined(string key)
{
// key is not joined if it occurs only at tails of expressions, e.g.
// a.B == null, a.B != null, a.B == c.D etc.
NhJoinClause nhJoinClause;
if (_joins.TryGetValue(key, out nhJoinClause))
{
nhJoinClause.MakeInner();
}
}
public bool CanAddJoin(Expression expression)
{
var source = QuerySourceExtractor.GetQuerySource(expression);
if (_queryModel.MainFromClause == source)
return true;
var bodyClause = source as IBodyClause;
if (bodyClause != null && _queryModel.BodyClauses.Contains(bodyClause))
return true;
var resultOperatorBase = source as ResultOperatorBase;
return resultOperatorBase != null && _queryModel.ResultOperators.Contains(resultOperatorBase);
}
private class QuerySourceExtractor : ExpressionTreeVisitor
{
private IQuerySource _querySource;
public static IQuerySource GetQuerySource(Expression expression)
{
var sourceExtractor = new QuerySourceExtractor();
sourceExtractor.VisitExpression(expression);
return sourceExtractor._querySource;
}
protected override Expression VisitQuerySourceReferenceExpression(QuerySourceReferenceExpression expression)
{
_querySource = expression.ReferencedQuerySource;
return base.VisitQuerySourceReferenceExpression(expression);
}
}
}
}