I have a EntityAttributeValue database that I have no control over. To get the data I use a stored proc as follows.
public class PhotoDataContext : DbContext, IPhotoDataContext
{
public IEnumerable<PhotoRegistration> GetPhotoRegistration()
{
return this.Database.SqlQuery<PhotoRegistration>("SP_Photo") ;
}
}
This works fine for when the POCO maps perfectly. Now I have a stored procedure that can return dynamic fields. All fields are of string type.
I am using EF 4.1 Code First and am passing the POCO's to Silverlight via WCF.
Any ideas how to stop the auto mapping of EF and to pivot the data back into a name value pair that WCF will be happy to serialize.
Thanks
J
Use ADO.NET = SqlConnection, SqlCommand, SqlDataReader (or equivalent if you don't use SQL Server). Entity framework doesn't like dynamic result sets.
Related
I used Entity Framework to create a prototype for a project and now that it's working I want to make the program ready for production.
I face many challenges with EF, the biggest one being the concurrency management (it's a financial software).
Given that it seems to have no way to handle pessimistic concurrency with EF, I have to switch to stored procs in SQL.
To be honest I'm a bit afraid of the workload that may represent.
I would like to know if anybody have been in the same situation before and what is the best strategy to convert a .net code using EF to raw SQL.
Edit:
I'm investigating CLR but it's not clear if pessimistic concurency can be manage with it. is it an option more interesting than TSQl in this case ? It would allow me to reuse part of my C# code and structure of function calling another functions, if I understand well.
I was there and the good news is you don't have to give up Entity Framework if you don't want to. The bad news is you have to update the database yourself. Which isn't as hard as it seems. I'm currently using EF 5 but plan to go to EF 6. I don't see why this still wouldn't work for EF 6.
First thing is in the constructor of the DbContext cast it to IObjectContextAdapter and get access to the ObjectContext. I make a property for this
public virtual ObjectContext ObjContext
{
get
{
return ((IObjectContextAdapter)this).ObjectContext;
}
}
Once you have that subscribe to the SavingChanges event - this isn't our exact code some things are copied out of other methods and redone. This just gives you an idea of what you need to do.
ObjContext.SavingChanges += SaveData;
private void SaveData(object sender, EventArgs e)
{
var context = sender as ObjectContext;
if (context != null)
{
context.DetectChanges();
var tsql = new StringBuilder();
var dbParams = new List<KeyValuePair<string, object>>();
var deletedEntites = context.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted);
foreach (var delete in deletedEntites)
{
// Set state to unchanged - so entity framework will ignore
delete.ChangeState(EntityState.Unchanged);
// Method to generate tsql for deleting entities
DeleteData(delete, tsql, dbParams);
}
var addedEntites = context.ObjectStateManager.GetObjectStateEntries(EntityState.Added);
foreach (var add in addedEntites)
{
// Set state to unchanged - so entity framework will ignore
add.ChangeState(EntityState.Unchanged);
// Method to generate tsql for added entities
AddData(add, tsql, dbParams);
}
var editedEntites = context.ObjectStateManager.GetObjectStateEntries(EntityState.Modified);
foreach (var edit in editedEntites)
{
// Method to generate tsql for updating entities
UpdateEditData(edit, tsql, dbParams);
// Set state to unchanged - so entity framework will ignore
edit.ChangeState(EntityState.Unchanged);
}
if (!tsql.ToString().IsEmpty())
{
var dbcommand = Database.Connection.CreateCommand();
dbcommand.CommandText = tsql.ToString();
foreach (var dbParameter in dbParams)
{
var dbparam = dbcommand.CreateParameter();
dbparam.ParameterName = dbParameter.Key;
dbparam.Value = dbParameter.Value;
dbcommand.Parameters.Add(dbparam);
}
var results = dbcommand.ExecuteNonQuery();
}
}
}
Why we set the entity to unmodified after the update because you can do
var changed properties = edit.GetModifiedProperties();
to get a list of all the changed properties. Since all the entities are now marked as unchanged EF will not send any updates to SQL.
You will also need to mess with the metadata to go from entity to table and property to fields. This isn't that hard to do but messing the metadata does take some time to learn. Something I still struggle with sometimes. I refactored all that out into an IMetaDataHelper interface where I pass it in the entity type and property name to get the table and field back - along with caching the result so I don't have to query metadata all the time.
At the end the tsql is a batch that has all the T-SQL how we want it with the locking hints and containing the transaction level. We also change numeric fields from just being set to nfield = 10 but to be nfield = nfield + 2 in the TSQL if the user updated them by 2 to avoid the concurrency issue as well.
What you wont get to is having SQL locked once someone starts to edit your entity but I don't see how you would get that with stored procedures as well.
All in all it took me about 2 solid days to get this all up and running for us.
I am a new to using Mongo DB and exploring the frameworks around for migrating from mysql to mongodb. So far from my findings I have been able to figure out SpringMongo as the best solution to my requirements.
The only problem is that instead of using a DSL based or abstract querying mechanism, I wished the framework allowed me to pass plain json string as arguments to the different methods exposed by the API(find, findOne) so that the query parameters can be written out to an external file (using a key to refer) and passed to the methods by reading and parsing at run time. But the framework should be capable of mapping the results to the domain objects.
Is there a way in spring-mongo to achieve this? Or is there any other frameworks on the same lines
You could use Spring Data to do that, just use the BasicQuery class instead of Query class. Your code will look like the following:
/* Any arbitrary string that could to parsed to DBObject */
Query q = new BasicQuery("{ filter : true }");
List<Entity> entities = this.template.find(q, Entity.class);
If you want more details:
http://static.springsource.org/spring-data/data-mongo/docs/current/reference/html/#mongo.query
http://static.springsource.org/spring-data/data-mongodb/docs/current/api/org/springframework/data/mongodb/core/query/BasicQuery.html
Well I got to find this one in the Spring data MongoOperations...
String jsonCommand = "{username: 'mickey'}";
MongoOperations mongoOps = //get mongooperations implemantation
mongoOps.executeCommand(jsonCommand)
It returns an instance of CommandResult that encapsulates the result.
I am developing an ASP.Net MVC 3 application using Entity Framework 4.1. For a particular complex query that I need to execute I have decided to write a raw SQL query and pass it to the built in dbSet.SqlQuery method.
I have a Service method like below where I assign the SQL query to a string variable called query. As the query is passed two parameters, I have parameterized these to prevent SQL Injection.
public IList<User> GetAvailableLocums(int shiftID, int shiftDateID)
{
var query ="Select .... where t1 = #p0 and t2 = #p1";
ObjectParameter _shiftID = new ObjectParameter("p0", shiftID);
ObjectParameter _shiftDateID = new ObjectParameter("p1", shiftDateID);
object[] parameters = new object[] { _shiftID, _shiftDateID };
return _UoW.User.GetWithRawSql(query, parameters).ToList();
}
I then pass the query and the parameters to a method in my repository which executes the query for me.
public IEnumerable<TEntity> GetWithRawSql(string query, params object[] parameters)
{
return dbSet.SqlQuery(query, parameters).ToList();
}
I know the query is correct as I have tested it in SQL Server Management Studio, however, I currently get the following error when I try to run this code
No mapping exists from object type System.Data.Objects.ObjectParameter
to a known managed provider native type
Does anyone have any suggestions as to how I can fix this?
Thanks for your help.
Folks
The problem was that I was using ObjectParameter to create my Parameters. I instead changed this to SqlParameter and it worked fine. See below.
Change from this
ObjectParameter _shiftID = new ObjectParameter("p0", shiftID);
To this
SqlParameter _shiftID = new SqlParameter("p0", shiftID);
And it worked. Hope this helps someone else.
From a quick Google search, it looks like your close. I think you are missing setting the return type for your SQL query:
return dbSet.SqlQuery<TEntity>(query, parameters).ToList();
This just tells Entity Framework how to map it.
I doubt this is just specific to NHibernate. But I have code as follows....
public class ClientController : ApiController
{
// GET /api/<controller>
public IQueryable<Api.Client> Get()
{
return Repositories.Clients.Query().Select(c => Mapper.Map<Client, Api.Client>(c));
}
I basically want to Query the database using the Odata criteria.... get the relevant 'Client' objects, and the convert them to the DTO 'Api.Client'.
But... the code as is, doesn't work. Because NHibernate doesn't know what to do the with the Mapper.... It really wants the query to come before the .Select. But I'm not sure I can get the Odata Query first?
It will work if I do
return Repositories.Clients.Query().Select(c => Mapper.Map<Client, Api.Client>(c)).ToList().AsQueryable();
But that's a bit sucky as you have to get ALL the clients from the database to do the OData query on.
Is there anyway to get the "Select" to happen after the OData query? Or another way to approach this?
I did not test it yet but the Open Source project NHibernate.OData could be useful for you.
The problem is that you are trying to execute C# code (Mapper.Map) inside the NH call (that is translated to SQL)
You'd have to map Api.Client manually, or create a Mapper implementation that returns an Expression<Func<Client, Api.Client>> and pass it directly as a parameter to Select().
Even with that, I'm not sure if NHibernate will translate it. But you can try.
AutoMapper supports this scenario with the Queryable Extensions
public IQueryable<Api.Client> Get() {
return Repositories.Clients.Query().Select(c => Mapper.Map<Client, Api.Client>(c));
}
becomes
public IQueryable<Api.Client> Get() {
return Repositories.Clients.Query().ProjectTo<Api.Client>(mapper.ConfigurationProvider);
}
I want to load some data with a SP.
I've put a SP in a Linq to SQL Class and I don't know how to use it for loading it's data in a datagrid.
In LinqToSqlDomainService I can't figure out how to call a SP.
What steps should I use.
Any samples of this ? All samples use a table.
Thank's
This post should hopefully be of help:
http://blogs.msdn.com/brada/archive/2009/08/24/business-apps-example-for-silverlight-3-rtm-and-net-ria-services-july-update-part-24-stored-procedures.aspx
You can create empty view with the same structure of your sproc and map that stored procedure to your function in your DomainService
See sample on http://cid-289eaf995528b9fd.skydrive.live.com/self.aspx/Public/sproc.zip
I found the following excellent step-by-step guide at this site -
http://betaforums.silverlight.net/forums/p/218383/521023.aspx
1) Add a ADO Entity Data Model to your Web project; Select generate from database option; Select your Database instance to connect to.
2) Choose your DB object to import to the Model. You can expand Table node to select any table you want to import to the Model. Expand Stored Procedure node to select your Stored Precedure as well. Click Finish to finish the import.
3) Right click the DB model designer to select Add/Function Import. Give the function a name (same name as your SP would be fine) and select the Stored Procedure you want to map. If your SP returns only one field, you can map the return result to a collection of scalars. If your SP returns more than one field, you could either map the return result to a collection or Entity (if all the field are from a single table) or a collection of Complex types.
If you want to use Complex type, you can click Get Column button to get all the columns for your SP. Then click Create new Complex type button to create this Complex type.
4) Add a Domain Service class to the Web project. Select the DataModel you just created as the DataContext of this Service. Select all the entitis you want expose to the client. The service functions should be generated for those entities.
5) You may not see the Complex type in the Entity list. You have to manully add a query function for your SP in your Service:
Say your SP is called SP1, the Complex type you generated is called SP1_Result.
Add the following code in your Domain Service class:
public IQueryable<SP1_Result> SP1()
{
return this.ObjectContext.SP1().AsQueryable();
}
Now you can compile your project. You might get an error like this: "SP1_Result does not have a Key" (if you not on RIA service SP1 beta). If you do, you need to do the following in the service metadata file:
Added a SP1_Result metadata class and tagged the Key field:
[MetadataTypeAttribute(typeof(SP1_Result.SP1_ResultMetadata))]
public partial class SP1_Result
{
internal sealed class SP1_ResultMetadata
{
[Key]
public int MyId; // Change MyId to the ID field of your SP_Result
}
}
6) Compile your solution. Now you have SP1_Result exposed to the client. Check the generated file, you should see SP1_Result is generated as an Entity class. Now you can access DomainContext.SP1Query and DomainContext.SP1_Results in your Silverlight code. You can treat it as you do with any other Entity(the entity mapped to a table) class.
Calling a stored procedure is trivial. Import it as a function and then invoke the function as a member of the DDS. The return value is an ObservableCollection<> that you can use to set up the DataContext of the object you want to bind.
...unless you want to use it in a Silverlight RIA app via the magic code generated proxy, in which case your goose is cooked unless your result rows exactly match one of the entities. If you can meet that criterion, edit the DomainService class and surface a method that wraps the ObjectContext method.