I'd like to store several different object types in a single Cosmos DB container, as they are all logically grouped and make sense to read together by timestamp to avoid extra HTTP calls.
However, the Cosmos DB client API doesn't seem to provide an easy way of doing the reads with multiple types. The best solution I've found so far is to write your own CosmosSerializer and JsonConverter, but that feels clunky: https://thomaslevesque.com/2019/10/15/handling-type-hierarchies-in-cosmos-db-part-2/
Is there a more graceful way to read items of different types to a shared base class so I can cast them later, or do I have to take the hit?
Thanks!
The way I do this is to create the ItemQueryIterator and FeedResponse objects as dynamic and initially read them untyped so I can inspect a "type" property that tells me what type of object to deserialize into.
In this example I have a single container that contains both my customer data as well as all their sales orders. The code looks like this.
string sql = "SELECT * from c WHERE c.customerId = #customerId";
FeedIterator<dynamic> resultSet = container.GetItemQueryIterator<dynamic>(
new QueryDefinition(sql)
.WithParameter("#customerId", customerId),
requestOptions: new QueryRequestOptions
{
PartitionKey = new PartitionKey(customerId)
});
CustomerV4 customer = new CustomerV4();
List<SalesOrder> orders = new List<SalesOrder>();
while (resultSet.HasMoreResults)
{
//dynamic response. Deserialize into POCO's based upon "type" property
FeedResponse<dynamic> response = await resultSet.ReadNextAsync();
foreach (var item in response)
{
if (item.type == "customer")
{
customer = JsonConvert.DeserializeObject<CustomerV4>(item.ToString());
}
else if (item.type == "salesOrder")
{
orders.Add(JsonConvert.DeserializeObject<SalesOrder>(item.ToString()));
}
}
}
Update:
You do not have to use dynamic types if want to create a "base document" class and then derive from that. Deserialize into the documentBase class, then check the type property check which class to deserialize the payload into.
You can also extend this pattern when you evolve your data models over time with a docVersion property.
Related
I want to set many to many relationship oid key name.
In many to many relationship Oid is created automatically but on database side I want to change oid name to custom name.
For Example;
If I try to create Person and Task many to many relation. Third table attributes in below;
KomutTanim (FK to Makine)
Makine (FK to KomutTanim)
OID (PK, guid)** (I want to set this key name??)**
Tell me how can I do. I added sample code in below
[Association("Relation.KomutListesi_Makine",typeof(KomutTanim),UseAssociationNameAsIntermediateTableName = true),XafDisplayName("Makine Komutları")]
public XPCollection<KomutTanim> Komutlar
{
get
{
return GetCollection<KomutTanim>(nameof(Komutlar));
}
}
[Association("Relation.KomutListesi_Makine", typeof(Makine), UseAssociationNameAsIntermediateTableName = true), XafDisplayName("Makineler")]
public XPCollection<Makine> MasterId
{
get
{
return GetCollection<Makine>(nameof(MasterId));
}
}
You can customize XPO metadata or manually create a persistent class for your intermediate table. These approaches are illustrated in the How to implement a many-to-many relationship with an intermediate table ticket.
The solution with customizing XPO metadata uses XAF APIs to access an XPClassInfo instance via the XPDictionary property. You can access XPDictionary using only XPO methods as illustrated at How to get an XPClassInfo instance. Also, you can manually create a ReflectionDictionary instance (ReflectionDictionary is an XPDictionary descendant) as described in the How to create persistent metadata on the fly and load data from an arbitrary table article.
XPDictionary dictionary = new ReflectionDictionary();
XPClassInfo intermediateClassInfo = dictionary.GetClassInfo(typeof(KomutTanim)).FindMember(nameof(KomutTanim.MasterId)).IntermediateClass;
intermediateClassInfo.FindMember("Oid").AddAttribute(new PersistentAttribute("MyName"));
string conn = "My connection string";
IDataStore store = XpoDefault.GetConnectionProvider(conn, AutoCreateOption.SchemaAlreadyExists);
IDataLayer dl = new SimpleDataLayer(dictionary, store);
XpoDefault.DataLayer = dl;
When creating a user, entries are required in multiple tables. I am trying to create a transaction that creates a new entry into one table and then pass the new entityid into the parent table and so on. The error I am getting is
The transaction manager has disabled its support for remote/network
transactions. (Exception from HRESULT: 0x8004D024)
I believe this is caused by creating multiple connections within a single TransactionScope, but I am unsure on what the best/most efficient way of doing this is.
[OperationBehavior(TransactionScopeRequired = true)]
public int CreateUser(CreateUserData createData)
{
// Create a new family group and get the ID
var familyGroupId = createData.FamilyGroupId ?? CreateFamilyGroup();
// Create the APUser and get the Id
var apUserId = CreateAPUser(createData.UserId, familyGroupId);
// Create the institution user and get the Id
var institutionUserId = CreateInsUser(apUserId, createData.AlternateId, createData.InstitutionId);
// Create the investigator group user and return the Id
return AddUserToGroup(createData.InvestigatorGroupId, institutionUserId);
}
This is an example of one of the function calls, all the other ones follow the same format
public int CreateFamilyGroup(string familyGroupName)
{
var familyRepo = _FamilyRepo ?? new FamilyGroupRepository();
var familyGroup = new FamilyGroup() {CreationDate = DateTime.Now};
return familyRepo.AddFamilyGroup(familyGroup);
}
And the repository call for this is as follows
public int AddFamilyGroup(FamilyGroup familyGroup)
{
using (var context = new GameDbContext())
{
var newGroup = context.FamilyGroups.Add(familyGroup);
context.SaveChanges();
return newGroup.FamilyGroupId;
}
}
I believe this is caused by creating multiple connections within a single TransactionScope
Yes, that is the problem. It does not really matter how you avoid that as long you avoid it. A common thing to do is to have one connection and one EF context per WCF request. You need to find a way to pass that EF context along.
The method AddFamilyGroup illustrates a common anti-pattern with EF: You are using EF as a CRUD facility. It's supposed to me more like a live object graph connected to the database. The entire WCF request should share the same EF context. If you move in that direction the problem goes away.
I'm newbie in SQLite.
I would like to query my SQLite database to get multiple rows.
When I add a new item in my local database I call this method Add:
public bool Add<T>(string key, T value)
{
return this.Insert(new SQliteCacheTable(key, this.GetBytes(value))) == 1;
}
_simpleCache.Add("favorite_1", data1);
_simpleCache.Add("favorite_2", data2);
_simpleCache.Add("favorite_3", data2);
Then,
I would like to retrieve from local database all entries where key starts with "favorite_"
to returns all objects in the database which are "favorite" objects.
I'm experienced in Linq, and I would like to do something like this:
IEnumerable<Element> = repository.Find((element) => element.Key.StartWith("favorite_"))
In the SQLiteConnection class there is a method like this:
SQLite.Net.SQLiteConnection.Find<T>(System.Linq.Expressions.Expression<System.Func<T,bool>>)
But I would like the same with in returns a collection IEnumerable<T>.
Can you help me please?
Thank you.
Jool
You have to build your query on the table itself, not the connection:
Assuming:
SQLiteConnection repository;
Then the code would look like:
var favorites = repository.Table<SQliteCacheTable>().Where(item => item.StartsWith("favorite_"));
The favorites variable is of type TableQuery<SQliteCacheTable> though, so it does not yet contain your data. The execution of the actual SQL query will be deferred until you try to access the results (by enumerating with foreach or converting to a list with ToList, for example).
To actually observe what's going on on the database, you can turn on tracing in sqlite-net, by setting repository.Trace = true on your SQLiteConnection object.
Finally, it's worth mentioning that you can also use the C# query syntax on TableQuery<T> objects, if your comfortable with it. So your query could become:
var favorites = from item in repository.Table<SQliteCacheTable>()
where item.StartsWith("favorite_")
select item;
Say for example if I have a business entity -> Customer, which has customerId, customerName and customerType. I have created an asp:Hidden Variable hdnCustomer to runat="server"
If I wanted to serialize the value of the customer business entity (in the code behind) to the hdnCustomer then how would I do that? Also once serialized how would I deserialize it?
// Pseudo code
Collection<Customer> customerList = new Collection<Customer>();
customerList = BusinessAccess.GetCustomerList();
hdnCustomer = serialize and assign the value of 'customerList' to hdnCustomer;
...
...
// Later on a select index change of one of the drop down lists
Inside the event handler for the drop down list:
{
Collection<Customer> customerList = new Collection<Customer>();
customerList = deserialize the value from hdnCustomer
int a = Convert.ToInt32(ddlDropDown.SelectedValue);
foreach(a in customerList)
{
// Do something
}
}
You can serialise to and from XML using XmlSerializer:
http://support.microsoft.com/kb/815813
However, if you just store the object in the ViewState[] collection that should work better:
ViewState["Customer"] = customerList;
It does the same thing: store the serialisable object in the page, hidden from the user: but it won't be in a human-readable format.
(edit: To deserialise, just get the value of ViewState["Customer"], checking for a null before using it!)
edit 2: a useful link about storing objects in ViewState:
http://www.beansoftware.com/ASP.NET-Tutorials/ViewState-In-ASP.NET.aspx
Hope that helps.
I think .net has already providing some classes to do so, look at this example
My problem is that I am trying to return a simple query that contains an object Story. The Story object has a UserId in the table which links to aspnet_users' UserId column. I have created a partial class for Story that adds the UserName property since it does not exist in the table itself.
The following query gets all stories; however, a pagination helper takes the query and returns only what's necessary once this is passed back to the controller.
public IQueryable<Story> FindAllStories(){
var stories = (from s in db.Stories
orderby s.DateEntered descending
select new Story
{
Title = s.Title,
StoryContent = s.StoryContent,
DateEntered = s.DateEntered,
DateUpdated = s.DateUpdated,
UserName = s.aspnet_User.UserName
}
);
return stories;
}
When the helper does a .count() on the source it bombs with the following exception:
"Explicit construction of entity type 'MyWebsite.Models.Story' in query is not allowed."
Any ideas? It's not a problem with the helper because I had this working when I simply had the UserName inside the Story table. And on a side note - any book recommendations for getting up to speed on LINQ to SQL? It's really kicking my butt. Thanks.
The problem is precisely what it tells you: you're not allowed to use new Story as the result of your query. Use an anonymous type instead (by omitting Story after new). If you still want Story, you can remap it later in LINQ to Objects:
var stories = from s in db.Stories
orderby s.DateEntered descending
select new
{
Title = s.Title,
StoryContent = s.StoryContent,
DateEntered = s.DateEntered,
DateUpdated = s.DateUpdated,
UserName = s.aspnet_User.UserName
};
stories = from s in stories.AsEnumerable() // L2O
select new Story
{
Title = s.Title,
StoryContent = s.StoryContent,
...
};
If you really need to return an IQueryable from your method and still need the Username of the user you can use DataContext.LoadOptions to eagerload your aspnet_user objects.
See this example.