We have a class, DelimitedPath, that contains functionality to store
string values that are delimited by a character, such as a namespace.
The class contains functionality to get different nodes of the string,
such as parent values, etc. The default delimiter is '.' but any
other character value can be specified. We have created a user type
that implements ICompositeUserType to store the delimiter as the
first character of the DelimitedPath value in the database, which
helps us parse the string into the individual nodes when retrieving
the value from the database.
Is there a way to "intercept" the value that the NHibernate.Linq 3.0
provider uses in a query so that we can add the delimiter character to
the beginning of a string when the DelimitedPath value is used in a
LINQ query? Developers may not know or don't need to know how the
data is stored in the database, so developers may not know what they
need to add the delimiter value to the beginning of any string in a
LINQ query, such as the query below:
IList<Privilege> privileges =
privilegePersister.Query().Where(
privilege =>
privilege.Resource.Path.Path.StartsWith("Cambridge.Framework").ToList();
The Path property of Resource is type DelimitedPath. The
DelimitedPath.Path property returns the entire value as a string,
which comes in handy as .ToString() cannot be used/is not supported in
the above LINQ query.
>From the Resource class:
/// <summary>
/// The namespace of the resource. Size is set to 450, which is the
max size for nvarchar in an index (i.e., unique constraint).
/// </summary>
public virtual DelimitedPath Path
>From the DelimitedPath class:
/// <summary>
/// The delimited path.
/// </summary>
public string Path
{
get
{
if (nodes == null) return null;
return string.Join(delimiter.ToString(), nodes);
}
}
The above query is parsed into the following SQL (some select columns
removed for brevity):
[Class=NHibernate.SQL]: select privilege0_.Id as Id9_, privilege0_.
[Version] as Version2_9_,
privilege0_.[IsAssignable] as IsAssign3_9_, privilege0_.RightId as
RightId9_,
privilege0_.ResourceId as ResourceId9_
from Framework.[Privilege] privilege0_, Framework.[Resource]
resource1_
where privilege0_.ResourceId=resource1_.Id and (resource1_.[Path] like
(@p0+'%'))
and resource1_.[ResourceHierarchyTypeId]=@p1;
@p0 = 'Cambridge.Framework' [Type: String (4000)], @p1 = 0 [Type:
Int32 (0)]
The above query returns zero rows because the data is stored as
follows:
.Cambridge.Framework
.Cambridge.Framework.Domain
Querying for "StartsWith(".Cambridge.Framework")" does bring back rows
from the database (as expected).
Is there a way to intercept the value used in a LINQ query, either
with ICompositeUserType or some other functionality?
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