private Expression BindFirst(Expression source, LambdaExpression predicate, string kind, bool isRoot)
{
DbProjectionExpression projection = this.VisitSequence(source);
Expression where = null;
if (predicate != null)
{
this.map[predicate.Parameters[0]] = projection.Projector;
where = this.Visit(predicate.Body);
}
Expression take = kind.StartsWith("First") ? Expression.Constant(1) : null;
if (take != null || where != null)
{
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(projection.Projector, alias, projection.Select.Alias);
projection = new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, where, null, null, false, null, take),
pc.Projector
);
}
if (isRoot)
{
Type elementType = projection.Projector.Type;
ParameterExpression p = Expression.Parameter(typeof(IEnumerable <>).MakeGenericType(elementType), "p");
LambdaExpression gator = Expression.Lambda(Expression.Call(typeof(Enumerable), kind, new Type[] { elementType }, p), p);
return(new DbProjectionExpression(projection.Select, projection.Projector, gator));
}
return(projection);
}
protected virtual Expression BindOrderBy(Type resultType, Expression source, LambdaExpression orderSelector, DbOrderType orderType)
{
List <DbOrderExpression> myThenBys = this.thenBys;
this.thenBys = null;
DbProjectionExpression projection = this.VisitSequence(source);
this.map[orderSelector.Parameters[0]] = projection.Projector;
List <DbOrderExpression> orderings = new List <DbOrderExpression>();
orderings.Add(new DbOrderExpression(orderType, this.Visit(orderSelector.Body)));
if (myThenBys != null)
{
for (int i = myThenBys.Count - 1; i >= 0; i--)
{
DbOrderExpression tb = myThenBys[i];
LambdaExpression lambda = (LambdaExpression)tb.Expression;
this.map[lambda.Parameters[0]] = projection.Projector;
orderings.Add(new DbOrderExpression(tb.OrderType, this.Visit(lambda.Body)));
}
}
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(projection.Projector, alias, projection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, null, orderings.AsReadOnly(), null),
pc.Projector
));
}
private Expression BindDistinct(Expression source)
{
DbProjectionExpression projection = this.VisitSequence(source);
DbSelectExpression select = projection.Select;
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(projection.Projector, alias, projection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, null, null, null, true, null, null),
pc.Projector
));
}
private Expression BindSkip(Expression source, Expression skip)
{
DbProjectionExpression projection = this.VisitSequence(source);
skip = this.Visit(skip);
DbSelectExpression select = projection.Select;
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(projection.Projector, alias, projection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, null, null, null, false, skip, null),
pc.Projector
));
}
private Expression BindSelect(Type resultType, Expression source, LambdaExpression selector)
{
DbProjectionExpression projection = this.VisitSequence(source);
this.map[selector.Parameters[0]] = projection.Projector;
Expression expression = this.Visit(selector.Body);
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(expression, alias, projection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, null),
pc.Projector
));
}
private Expression BindWhere(Type resultType, Expression source, LambdaExpression predicate)
{
DbProjectionExpression projection = this.VisitSequence(source);
this.map[predicate.Parameters[0]] = projection.Projector;
Expression where = this.Visit(predicate.Body);
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(projection.Projector, alias, projection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, where),
pc.Projector
));
}
protected virtual Expression BindJoin(Type resultType, Expression outerSource, Expression innerSource, LambdaExpression outerKey, LambdaExpression innerKey, LambdaExpression resultSelector)
{
DbProjectionExpression outerProjection = this.VisitSequence(outerSource);
DbProjectionExpression innerProjection = this.VisitSequence(innerSource);
this.map[outerKey.Parameters[0]] = outerProjection.Projector;
Expression outerKeyExpr = this.Visit(outerKey.Body);
this.map[innerKey.Parameters[0]] = innerProjection.Projector;
Expression innerKeyExpr = this.Visit(innerKey.Body);
this.map[resultSelector.Parameters[0]] = outerProjection.Projector;
this.map[resultSelector.Parameters[1]] = innerProjection.Projector;
Expression resultExpr = this.Visit(resultSelector.Body);
DbJoinExpression join = new DbJoinExpression(DbJoinType.InnerJoin, outerProjection.Select, innerProjection.Select, outerKeyExpr.Equal(innerKeyExpr));
var alias = this.GetNextAlias();
ProjectedColumns pc = this.ProjectColumns(resultExpr, alias, outerProjection.Select.Alias, innerProjection.Select.Alias);
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, join, null),
pc.Projector
));
}
protected virtual Expression BindGroupBy(Expression source, LambdaExpression keySelector, LambdaExpression elementSelector, LambdaExpression resultSelector)
{
DbProjectionExpression projection = this.VisitSequence(source);
this.map[keySelector.Parameters[0]] = projection.Projector;
Expression keyExpr = this.Visit(keySelector.Body);
Expression elemExpr = projection.Projector;
if (elementSelector != null)
{
this.map[elementSelector.Parameters[0]] = projection.Projector;
elemExpr = this.Visit(elementSelector.Body);
}
// Use ProjectColumns to get group-by expressions from key expression
ProjectedColumns keyProjection = this.ProjectColumns(keyExpr, projection.Select.Alias, projection.Select.Alias);
IEnumerable <Expression> groupExprs = keyProjection.Columns.Select(c => c.Expression);
// make duplicate of source query as basis of element subquery by visiting the source again
DbProjectionExpression subqueryBasis = this.VisitSequence(source);
// recompute key columns for group expressions relative to subquery (need these for doing the correlation predicate)
this.map[keySelector.Parameters[0]] = subqueryBasis.Projector;
Expression subqueryKey = this.Visit(keySelector.Body);
// use same projection trick to get group-by expressions based on subquery
ProjectedColumns subqueryKeyPC = this.ProjectColumns(subqueryKey, subqueryBasis.Select.Alias, subqueryBasis.Select.Alias);
IEnumerable <Expression> subqueryGroupExprs = subqueryKeyPC.Columns.Select(c => c.Expression);
Expression subqueryCorrelation = this.BuildPredicateWithNullsEqual(subqueryGroupExprs, groupExprs);
// compute element based on duplicated subquery
Expression subqueryElemExpr = subqueryBasis.Projector;
if (elementSelector != null)
{
this.map[elementSelector.Parameters[0]] = subqueryBasis.Projector;
subqueryElemExpr = this.Visit(elementSelector.Body);
}
// build subquery that projects the desired element
var elementAlias = this.GetNextAlias();
ProjectedColumns elementPC = this.ProjectColumns(subqueryElemExpr, elementAlias, subqueryBasis.Select.Alias);
DbProjectionExpression elementSubquery =
new DbProjectionExpression(
new DbSelectExpression(elementAlias, elementPC.Columns, subqueryBasis.Select, subqueryCorrelation),
elementPC.Projector
);
var alias = this.GetNextAlias();
// make it possible to tie aggregates back to this group-by
GroupByInfo info = new GroupByInfo(alias, elemExpr);
this.groupByMap.Add(elementSubquery, info);
Expression resultExpr;
if (resultSelector != null)
{
Expression saveGroupElement = this.currentGroupElement;
this.currentGroupElement = elementSubquery;
// compute result expression based on key & element-subquery
this.map[resultSelector.Parameters[0]] = keyProjection.Projector;
this.map[resultSelector.Parameters[1]] = elementSubquery;
resultExpr = this.Visit(resultSelector.Body);
this.currentGroupElement = saveGroupElement;
}
else
{
// result must be IGrouping<K,E>
resultExpr =
Expression.New(
typeof(Grouping <,>).MakeGenericType(keyExpr.Type, subqueryElemExpr.Type).GetConstructors()[0],
new Expression[] { keyExpr, elementSubquery }
);
resultExpr = Expression.Convert(resultExpr, typeof(IGrouping <,>).MakeGenericType(keyExpr.Type, subqueryElemExpr.Type));
}
ProjectedColumns pc = this.ProjectColumns(resultExpr, alias, projection.Select.Alias);
// make it possible to tie aggregates back to this group-by
NewExpression newResult = this.GetNewExpression(pc.Projector);
if (newResult != null && newResult.Type.IsGenericType && newResult.Type.GetGenericTypeDefinition() == typeof(Grouping <,>))
{
Expression projectedElementSubquery = newResult.Arguments[1];
this.groupByMap.Add(projectedElementSubquery, info);
}
return(new DbProjectionExpression(
new DbSelectExpression(alias, pc.Columns, projection.Select, null, null, groupExprs),
pc.Projector
));
}
