private bool ReplaceAxisCallback(Expression node, object[] noargs) // note: internal longhorn name found on www.winfx247.com
{
if( node.NodeType == NodeType.Axis )
{
Axis axis = (Axis)node;
// convert the axis into a filter (don't want any axis nodes in final tree)
Expression filter = new Filter(axis);
// see if we need to wrap the filter with an exist node
// note: this is needed when:
// 1) the source property of the axis is relational
// 2) the parent of the axis is not already an exists (for future support for the exists keyword)
// 3) the axis is not in the source of its parent filter
if( axis.Owner.NodeType != NodeType.Unary || ((Unary)axis.Owner).Operator != UnaryOperator.Exists )
{
// get the source property for this axis
Property property;
if( axis.Source.NodeType == NodeType.Property )
{
property = (Property)axis.Source;
}
else if( axis.Source.NodeType == NodeType.Filter || axis.Source.NodeType == NodeType.Axis )
{
property = (Property)(axis.Source as Filter).Source;
}
else // source not property, filter, or axis
{
throw new Exception("Axis source node type of '" + axis.Source.NodeType + "' was not expected.");
}
if( property.IsRelational )
{
// find the containing filter for this axis (there has to be one) and track the child
Expression child = axis;
Expression parent = axis.Owner;
while( parent != null && parent.NodeType != NodeType.Filter )
{
child = parent;
parent = parent.Owner;
}
if( parent == null )
{
throw new Exception("Axis node is not contained in a Filter node. Assumption failed.");
}
if( ((Filter)parent).Source != child ) // axis not in source of filter
{
filter = new Unary(UnaryOperator.Exists, filter);
}
}
}
// do the replacement
Expression.Replace(axis, filter);
}
return true;
}
private void WriteFilterConstraints(TextWriter w, Filter filter, bool whereStarted)
{
// add any source constraints in a nested filter
if( filter.Source.NodeType == NodeType.Filter )
{
Filter sourceFilter = (Filter)filter.Source;
sourceFilter.Alias = filter.Alias;
if( !whereStarted )
{
w.Write("\nWHERE ");
whereStarted = true;
}
else
{
w.Write(' ');
w.Write(GetSqlKeyword(BinaryOperator.LogicalAnd));
w.Write(' ');
}
WriteSqlQuery(w, sourceFilter.Constraint);
}
// add the filter constraints
if( filter.Constraint.NodeType != NodeType.Empty )
{
if( !whereStarted )
{
w.Write("\nWHERE ");
whereStarted = true;
}
else
{
w.Write(' ');
w.Write(GetSqlKeyword(BinaryOperator.LogicalAnd));
w.Write(' ');
}
WriteSqlQuery(w, filter.Constraint);
}
}
