ajj3085 posted on Wednesday, March 05, 2008
Hi,
I have a wierd problem with Linq. I have the following code in my fetch method:
/// <summary>Loads the list.</summary>
/// <param name="documentHistoryId">The document
/// for which to get items.</param>
/// <param name="db">The connection to use.</param>
/// <param name="taxRate">The tax rate items
/// should use when loading.</param>
private void LoadSelf(
int documentHistoryId,
decimal? taxRate,
MedDataDataContext db
) {
var items =
from lineitems in db.LineItemHistory
where lineitems.DocumentHistoryId == documentHistoryId &&
lineitems.ParentLineItemId == null
orderby lineitems.Position
select lineitems;
IsReadOnly = false;
foreach ( var item in items ) {
LineItemRevision lineRev = LineItemRevision.GetItem( item, 0, taxRate, db );
Add( lineRev );
if ( LoadChildren(
documentHistoryId,
item.LineItemId.Value,
0,
taxRate,
db
) ) {
lineRev.IsGroupStart = true;
}
}
IsReadOnly = true;
}
/// <summary>Loads the list.</summary>
/// <param name="documentHistoryId">The document
/// for which to get items.</param>
/// <param name="db">The connection to use.</param>
/// <param name="taxRate">The tax rate items
/// should use when loading.</param>
/// <param name="parentLineItemId">The id of
/// the parent for items to load.</param>
/// <param name="depth">The depth of the items
/// being loaded.</param>
private bool LoadChildren(
int documentHistoryId,
int parentLineItemId,
int depth,
decimal? taxRate,
MedDataDataContext db
) {
int childCount;
var items =
from lineitems in db.LineItemHistory
where lineitems.DocumentHistoryId == documentHistoryId &&
lineitems.ParentLineItemId == parentLineItemId
orderby lineitems.Position
select lineitems;
childCount = 0;
depth += 1;
foreach ( var item in items ) {
LineItemRevision lineRev;
childCount += 1;
lineRev = LineItemRevision.GetItem( item, depth, taxRate, db );
Add( lineRev );
if ( LoadChildren(
documentHistoryId,
item.LineItemId.Value,
depth,
taxRate,
db
) ) {
lineRev.IsGroupStart = true;
}
}
return childCount > 0;
}
So, you notice that the queries are identical in both LoadSelf and LoadChildren. It seems natural that I make LoadSelf simplier by changing it to this:
private void LoadSelf(
int documentHistoryId,
decimal? taxRate,
MedDataDataContext db
) {
IsReadOnly = false;
LoadChildren(
documentHistoryId,
null
-1,
taxRate,
db
);
IsReadOnly = true;
}
And I make LoadChildren take a Int32? instead of just an Int32. For some reason, making these chagnes causes linq to mess up the query. Instead of specifying ParentLineItemId IS NULL, it tries ParentLineItemId = Null, which of course never works.
Any ideas?
