I'm trying to create a new Dictionary and inject it in the IORegistry. I've managed to inject simple strings or data values but thats it.
My approach is via a modified IOPCIFamily.kext, and it's not for a specific purpose but just for learning.
My code for 1 line values is something like this
if (product == id){ setProperty("test", "test") }
and another approach
if (product == id){ propTable->setObject("TEST", prop) prop->release(); }
propTable is the Parent Dictionary, so i must create a child Dictionary to which i can inject values with setObject parameter.
Does anyone have an idea on how to do this? I suspect it must be something like this:
propTable->newTable->setObject(etc)
but i didn't figure how to create the newTable for propTable to insert it in the existing one of what ever product == ids it finds.
Thank you very much, sorry if it's confusing. Not used to explain code related stuff in english.
If I understand your question correctly, you want the OSDictionary::withCapacity factory function.
For example:
OSDictionary* prop_dict = OSDictionary::withCapacity(1);
OSString* val = OSString::withCString("test");
if (!prop_dict || !val)
{
// handle error...
}
prop_dict->setObject("test", val);
val->release(); val = NULL;
and then, to use it in you property table:
propTable->setObject("NewProperty", prop_dict);
prop_dict->release(); prop_dict = NULL;
Related
I'm using LINQ to SQL to obtain data from a set of database tables. The database design is such that given a unique ID from one table (Table A) one and only one instance should be returned from an associated table (Table B).
Is there a more concise way to compose this query and ensure that only one item was returned without using the .Count() extension method like below:
var set = from itemFromA in this.dataContext.TableA
where itemFromA.ID == inputID
select itemFromA.ItemFromB;
if (set.Count() != 1)
{
// Exception!
}
// Have to get individual instance using FirstOrDefault or Take(1)
FirstOrDefault helps somewhat but I want to ensure that the returned set contains only one instance and not more.
It sounds like you want Single:
var set = from itemFromA in this.dataContext.TableA
where itemFromA.ID == inputID
select itemFromA.ItemFromB;
var onlyValue = set.Single();
Documentation states:
Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
Of course that means you don't get to customize the message of the exception... if you need to do that, I'd use something like:
// Make sure that even if something is hideously wrong, we only transfer data
// for two elements...
var list = set.Take(2).ToList();
if (list.Count != 1)
{
// Throw an exception
}
var item = list[0];
The benefit of this over your current code is that it will avoid evaluating the query more than once.
I want to add some calculated properties to an EntityObject without loosing the possibility of querying it agains the database.
I created a partial class and added the fields I need in the object. Than I wrote a static function "AttachProperties" that should somehow add some calculated values. I cannot do this on clientside, since several other functions attach some filter-conditions to the query.
The functions should look like this:
return query.Select(o =>
{
o.HasCalculatedProperties = true;
o.Value = 2;
return o;
});
In my case the calculated value depends on several lookups and is not just a simple "2". This sample works with an IEnumerable but, of course, not with an IQueryable
I first created a new class with the EntityObject as property and added the other necessary fields but now I need this extended class to be of the same basetype.
First, in my opinion changing objects in a Select() is a bad idea, because it makes something else happen (state change) than the method name suggests (projection), which is always a recipe for trouble. Linq is rooted in a functional programming (stateless) paradigm, so this kind of usage is just not expected.
But you can extend your class with methods that return a calculation result, like:
partial class EntityObject
{
public int GetValue()
{
return this.MappedProp1 * this.MappedProp2;
}
}
It is a bit hard to tell from your question whether this will work for you. If generating a calculated value involves more than a simple calculation from an object's own properties it may be better to leave your entities alone and create a services that return calculation results from an object graph.
Try something like this:
return from o in collection
select new O()
{
OtherProperty = o.OtherProperty,
HasCalculatedProperties = true,
Value = 2
};
This will create a copy of the original object with the changes you require and avoid all the messiness that come with modifying an entity in a select clause.
I have an Abstract type called Product, and five "Types" that inherit from Product in a table per type hierarchy fashion as below:
I want to get all of the information for all of the Products, including a smattering of properties from the different objects that inherit from products to project them into a new class for use in an MVC web page. My linq query is below:
//Return the required products
var model = from p in Product.Products
where p.archive == false && ((Prod_ID == 0) || (p.ID == Prod_ID))
select new SearchViewModel
{
ID = p.ID,
lend_name = p.Lender.lend_name,
pDes_rate = p.pDes_rate,
pDes_details = p.pDes_details,
pDes_totTerm = p.pDes_totTerm,
pDes_APR = p.pDes_APR,
pDes_revDesc = p.pDes_revDesc,
pMax_desc = p.pMax_desc,
dDipNeeded = p.dDipNeeded,
dAppNeeded = p.dAppNeeded,
CalcFields = new DAL.SearchCalcFields
{
pDes_type = p.pDes_type,
pDes_rate = p.pDes_rate,
pTFi_fixedRate = p.pTFi_fixedRate
}
}
The problem I have is accessing the p.pTFi_fixedRate, this is not returned with the Products collection of entities as it is in the super type of Fixed. How do I return the "super" type of Products (Fixed) properties using Linq and the Entity Framework. I actually need to return some fields from all the different supertypes (Disc, Track, etc) for use in calculations. Should I return these as separate Linq queries checking the type of "Product" that is returned?
This is a really good question. I've had a look in the Julie Lerman book and scouted around the internet and I can't see an elegant answer.
If it were me I would create a data transfer object will all the properties of the types and then have a separate query for each type and then union them all up. I would insert blanks into the DTO properies where the properties aren't relevant to that type. Then I would hope that the EF engine makes a reasonable stab at creating decent SQL.
Example
var results = (from p in context.Products.OfType<Disc>
select new ProductDTO {basefield1 = p.val1, discField=p.val2, fixedField=""})
.Union(
from p in context.Products.OfType<Fixed>
select new ProductDTO {basefield1 = p.val1, discField="", fixedField=p.val2});
But that can't be the best answer can it. Is there any others?
So Fixed is inherited from Product? If so, you should probably be querying for Fixed instead, and the Product properties will be pulled into it.
If you are just doing calculations and getting some totals or something, you might want to look at using a stored procedure. It will amount to fewer database calls and allow for much faster execution.
Well it depends on your model, but usually you need to do something like:
var model = from p in Product.Products.Include("SomeNavProperty")
.... (rest of query)
Where SomeNavProperty is the entity type that loads pTFi_fixedRate.
LINQ newbie here
I am trying to get a value of a field - using a fieldName variable.
If I do a watch on row[FieldName] I do get a value - but when I do it on the actual code it will not compile.
string fieldName = "awx_name"
List<awx_property> propertyQry =
(
from property in crm.awx_propertyawx_properties
where property.awx_propertyid == new Guid(id)
select property
).ToList();
foreach (awx_property row in propertyQry)
{
//THIS DOES NOT WORK
fieldValue = row[fieldName];
}
Thanks in advance. Alternatives would be welcome as well
You keep us guessing what you are trying to do here... You need to specify the types of the objects, so it's easy for us to understand and help. Anyway, I think you are trying to get an object based on the ID. Since you are getting by Id, my guess would be the return value is a single object.
var propertyObj =( from property in crm.awx_propertyawx_properties
where property.awx_propertyid == new Guid(id)
select property
).SingleOrDefault();
if(propertyObj != null) {
fieldValue = propertyObj.GetType().GetProperty(fieldName).GetValue(propertyObj, null);
}
Of course, you need to add validation to make sure you don't get null or any other error while accessing the property value.
Hope it helps.
What type is fieldValue? What does awx_property look like? This will only work is awx_property is a key/value collection. It its not, you could use reflection instead.
If it is a key/value collection you are probably missing a cast. (row[FieldName].ToString() or something) Also you are missing a semi-colon in the foreach block.
Hi I been searching for my error but I can't find anything that help me. The problem is this. I been working with Subsonic 3, Newtonsoft Json and the linq way of write so I have this easy query:
var found = from client in newclients.All() where client.Period == "sometext" select client;
string periodoJSON = JsonConvert.SerializeObject(periodoFound); //this get "Self referencing loop Exception"
the problem is when I run this script I get the horrible exception "Self referening loop exception" in the JsonConvert line, subsonic have all the objects without any problem but if I do the following.
var found = from client in newclients.All() where client.Period == "sometext" select new client{client.Name, client.LastName, etc};
string periodoJSON = JsonConvert.SerializeObject(periodoFound);
I get the object serialize with a any problem with all the properties. I'm doing the last way because I have to finish my work but is any other way or solution for this problem, if not I will have to write all the properties every time I want to get a full table properties.
hope any can solve my problem o help me in the path for find a solution....
what I have is a really basic query with linq and I try the three values for JsonSerializerSettings and any work, again I'm working with subsonic 3 this not happend either with subsnoic 2 and I can make it work if I specify one by one the properties of the object in the linq query does any have any clue of what is happend, ANY more help would be great!!! If I put the value of Serialize my page get crazy and in a infinity loop state, if I decide for error simple doesn't work and Ignore nothing happen... some more information about this self referencia loop?
var u = usuario.SingleOrDefault(x => x.TipoUsuario == "A" || x.TipoUsuario == "W");
JsonSerializerSettings setting = new JsonSerializerSettings();
setting.ReferenceLoopHandling = ReferenceLoopHandling.Error; //.Serialize .Ignore
Page.ClientScript.RegisterClientScriptBlock(this.GetType(),"usuario", "var usuario=" + JsonConvert.SerializeObject(u, Formatting.None, setting) + ";");
Update ------
I code the following
string jsU = JsonConvert.SerializeObject(u,Formatting.None,new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects, ReferenceLoopHandling = ReferenceLoopHandling.Ignore });
and is workign but the only thing wrongs is that in the json object comes all the information about the columns of subsonic 3 and a BIG chunk of text explain it... does any one know how to not SEND this part of the object??
Without knowing more about you object model it is hard to provide a definitive answer, but I would take a look at the ReferenceLoopHandling enum.
You're calling string SerializeObject(object value) on JsonConvert. Try the string SerializeObject(object value, Formatting formatting, JsonSerializerSettings settings) method instead. The JsonSerializerSettings settings parameter lets you set a bunch of things, including the ReferenceLoopHandling ReferenceLoopHandling { get; set; } property.
You can try these values:
public enum ReferenceLoopHandling
{
Error,
Ignore,
Serialize
}
Obviously, Error is the default and that's what you're getting. Perhaps one of the others will help.