I'm using CodeFluent Entities to manage my database for a ASPNET MVC3 web application. I would like to find a way to configure a Property of an Entity in my Model which would be 'transparently' managed with EncryptByPassPhrase and DecryptByPassPhrase TSQL functions.
Example TSQL INSERT/UPDATE (property 'Text') :
-> Add a #PassPhrase(?) parameter to send my key string
-> replace '#Text' by 'EncryptByPassPhrase(#PassPhrase,#Text)
Example TSQL LOAD/SEARCH (property 'Text') :
-> Add a #PassPhrase(?) parameter to send my key string
-> replace '#Text' by 'DecryptByPassPhrase(#PassPhrase,#Text)
Basically, I want to save an encrypted data (from a clear text) and retrieve a decrypted data (from the encrypted field value), without writing stored procedure on my own.
I know I can solve my problem it by creating a custom SQL Stored Procedure for both Save() and Load*() methods, but it seems to me that a tool like CodeFluent Entities might provide a way to feed my needs.
Thanks to anyone that can help me on that ;)
Before anything is actually generated, CodeFluent Entities parses the model and transforms it into a complete memory representation which contains Entities, Properties, Methods, Tables, Columns, Procedures, etc. The inference engine that does this transformation is using a pipeline that’s divided into steps. CodeFluent Entities Aspects can be introduced at any step, and are able to modify the model currently in memory, therefore influencing the next steps.
How to write an aspect is too long to be explained on SO.
You’ll find my complete answer at: http://blog.codefluententities.com/2013/09/25/writing-a-custom-codefluent-entities-aspect-to-encrypt-decrypt-columns-values-at-runtime/
Related
We would like to create an OData REST API. Our data model is such that each customer has their own database. All database objects have the same definition across all customer databases, with the exception of a single table.
The customer specific table we will call Contact. When a customer adds a column the system creates a column with a standardised name with a definition translated from options selected by the user in the UI. The user only refers to the column data by a field name they have specified to enable the user to be able to generate friendly queries.
It seems to me that the following approaches could be used to enable OData for the model described:
1) Create an OData open type to cater for the dynamic properties. This has the disadvantage of user requests for a customer not providing an indication of the dynamic properties that can be queried against. Even though they will be known for the user (via token authentication). Also, because dynamic properties are a dictionary, some data pivoting and inefficient query writing would be required. Not sure how to implement the IQueryable handling of query options for the dynamic properties to enable our own custom field querying.
2) Create a POCO class with e.g. 50 properties; CustomField1, CustomField2... Then somehow control which fields are exposed for use in OData calls. We would then include a separate API call to expose the custom field mapping. E.g. custom field friendly name of MobileNumber = CustomField12.
3) At runtime, check to see if column definitions of table changed since last check. If have, generate class specific to customer using CodeDom and register it with OData. Aiming for a unique URL for each customer. E.g. http://domain.name/{customer guid}/odata
I think the ideal for us is option 2. However, the fact the CustomField1 could be an underlying SQL data type of nvarchar, int, decimal, datetime, etc, there are added complications.
Has anyone a working example of how to achieve what has been described, satisfactorily?
Thanks in advance for any help.
Rik
We have run into a similar situation but with our entire dataset being unknown until runtime. Using the ODataConventionModelBuilder and EdmModel classes, you can add properties dynamically to the model at runtime.
I'm not sure whether you will have to manually add all of the properties for this object type even though only some of them are unknown or whether you can add your main object and then add your dynamic ones afterwards, but I guess either would be workable.
If you can get hold of which type of user it is on the server, you could then add only the properties that you are interested in (like option 3 but not having to CodeDom).
There is an example of this kind of untyped OData server in the OData samples here that should get you started: https://github.com/OData/ODataSamples/tree/master/WebApi/v4/ODataUntypedSample
The research we carried out actually posed Option 1 as the most suitable approach for some operations. i.e. Create an SQL view that unpivots the data in a table to a key/value pair of column name/column value for each column in the table. This was suitable for queries returning small datasets. This was far less effort than Option 3 and less confusing for the user than Option 2. The unpivot query converted the field values to nvarchar (string) values and thus meant that filtering in the UI by column value data types was not simple to achieve. (If we decide to implement this ability, I believe this can be achieved by creating a custom attribute that derives from EnablQueryAttribute, marking the controller action with it and manipulate the IQueryable before execution).
However, we wanted to expose a /Contacts/Export endpoint that when called would output the columns from a table with a fixed schema joined on a table with a client specific schema and output to a CSV file. All the while utilising the OData supported filter syntax. One of our customer databases has more than 12 million rows of data and is made up of approximately 30 columns.
To achieve this it looks like our best bet would have been to work with the Microsoft.OData.Core.UriParser.UriQueryExpressionParser class, unfortunately Microsoft in their wisdom have declared this as internal, as well as many of it's dependants.
Walking an abstract syntax tree built from OData supported query options and applying our own visitor to each node to build some dynamic Linq query/SQL seems like a possible solution.
For the time-being we will simply implement a cut-down set of supported $filter criteria without the support for grouping parenthesis.
I'm working with a legacy database that I can't easily create an entity model over because it uses extension tables with what is effectively composite keys and EF only supports single column keys for mapping one entity to multiple tables.
So, what I've decided to do is create updatable views (with INSTEAD OF triggers to handle CRUD operations) over the top of the legacy tables (which cannot be touched) and then have my entity model (either using EF or DevExpress XPO) built on top of the database views. This will also allow me to do stuff like easily add sub-queries in the select clause to retrieve child counts on parent records when retrieving a list of parent records in a single query.
However, I don't particularly want to manually write the SQL for all the views and triggers so I thought I'd use data model defined in the .EDMX file and t4 templates to help me generate the bulk of the T-SQL needed to create the views and the triggers. I thought there would be some template that I could use as the basis for doing this, but seems that's not so easy to find.
Can someone please suggest a t4 template that I could use as the basis where mappings are being retrieved from the .EDMX. Alternatively can anyone advise how to use the StorageMappingItemCollection to retrieve the mapping information from the EDMX file. I know a few people have said that apparently you can't use it or that they just use Linq to Xml, but I would have thought it should certainly be possible to use the StorageMappingItemCollection class as a strongly typed class to access this data.
Any examples of how I could use StorageMappingItemCollection to access mapping info would be very helpful. Thanks.
See http://brewdawg.github.io/Tiraggo.Edmx/ you can install it via NuGet within Visual Studio and it serves up all of the metadata from your EDMX files that Microsoft hides from you, very simple, works great.
I have the below scenario. I am using EF 5 Code first, MVC 4 on VS 2010. I am using the Unit of Work and Repository pattern for my project.
I am not sure if this is possible or not. Kindly suggest.
I have a model class representing a database table. In the model class, I have a property that is decorated as [NotMapped]. I have a Stored Proc that returns data, similar to the model class. However, when I get the data in a List from the SP, it does not contain value for the [NotMapped] column (SP returns data for the [NotMapped] column though). This may be logically correct with respect to EF.
All I want to know is, do we have a way to get data populated for the [NotMapped] column. I want to achieve, CRUD using LINQ (excluding R - Read).
I would recommend to create a separate complex type for the stored procedure results. Otherwise sooner or later you will find yourself writing code to distinguish between entities coming from the DbSet or from the stored procedure. When the come from the stored procedure they can't be used in joins, for example. Or checks whether or not the unmapped property is set.
A very dirty approach could be to have two different contexts. With code first it is possible to have different contexts with different mappings to the same types, with and without the column ignored (if you use fluent mapping, not with data annotations). But that only succeeds if you tell EF not to check the database schema, so using migrations is ruled out as well. I would not do it!! For the same reason as I mentioned above. I would hate to have a type with a property that sometimes is and sometimes isn't set.
I did work on ADO.NET Entity Framework v2 about two years ago. I have faint memories.
Incidentally, I happen to be working in a very secured (for want of a euphemism) environment where a lot of links are blocked and there's not much one can do. It does get in the way of studying and working, more than a bit.
Therefore, I have to rely on this forum for a few basic questions I have to get started again. This time, I am working on Entity Framework 4. Here are my questions.
All these questions relate to the EDM generated entities, i.e. not the Code First model.
1) Is my understanding correct? I can rename any column name in the EDM designer generated model and nothing breaks.
2) Foreign keys are expressed as navigational properties in the generated entity classes. No special consideration is required to maintain foreign key relationships. I recall in version 1 of EF, you had just ID properties and the navigational IQueryable/IEnumerable/EntityCollection/RelatedEnd properties were introduced in version 2. I just need to know if I need to do anything to retain/maintain foreign key relationships and referential data integrity. I assume I don't need to. A confirmation would be nice.
3) What are all the possible ways to execute a stored procedure? I recall -- one way to use ExecuteSQL or something on the Context.Database object, another to use EntityClient API and the third was to specify stored procedure names in the InsertCommand, SelectCommand, etc. thingies in the mapping window of the EDM designer. Is this correct?
4) How do you use those SelectCommand thingies in the mapping window on an entity? Do you just supply the names of the stored procedures or user defined SQL functions?
5) How do I create an entity out of a subset of a table? Do I just create an entity from the table and then delete the columns I don't need from the designer? What happens if there are required (NOT NULL in SQL) values that are not in the subset I choose?
6) How do I create a table out of a query or join of two or more tables.
1) You can rename columns in the designer and nothing should break (if the name is valid)
2) Navigation properties point to related entities. In EF4 foreign keys were added. Foreign key properties basically expose the database way of handling relations. However, they are helpful since you don't have to load related entities just to change relationship - you can just change the key value to the id of the other entity and save your changes
3) Yes. You can either execute the procedure directly - this is for stored procedures that are not related to CUD (Create/Update/Delete) operations. You can map CUD operations to stored procedure as opposed to having EF execute SQL statements it came up with for your CUD operations.
4) I think this is a bit out of scope - you probably can find a lot of blogs with images how to do it. Any decent book on EF should also have a chapter (or two) on this. Post a question to stackoverflow if you hit a specific problem.
5) Remove properties in the designer and then supply default value to the S-Space definition. I believe you cannot do this with the designer. You need to rightclick on the edmx file and open it with the Xml editor and manually edit it. Also see this: Issue in EF, mapping fragment,no default value and is not nullable
6) You can either create a view in the database or you can create entity set using E-SQL in your edmx file (I think this will be read only though) or you may be able to use Entity Splitting. Each of these is probably a big topic itself so I think you should find more about these and come back if you have more specific questions / problems
I have an existing database with a set of stored procedures. I am redesigning the application layer without making changes to database objects. One of the difficulties I am faced with is there are many stored procedures which are similar to each other in that they query the same tables but return different combinations of columns.
I am neither able to return partially filled entities nor I could find a way to return anonymous types from stored procedures using Entity Framework 4.1 (and SQL Server 2008 R2). This is forcing me to define too many complex types one per stored procedure although underlying table structure is the same.
My questions are :
Please suggest solutions for minimising number of entities / complex types which can be implemented using EF and without making changes to database objects.
Also, is it possible to return partially filled entities? This would enable me to reuse entities. I am not planning to use object tracking features.
How can we return anonymous types from stored procedures outputs? This is also good enough for me since in most cases I am going to return the data to client in JSON format
Thanks
You won't be able to return anonymous types - those are typically restricted to the scope of the method they're defined inside of.
Returning partially filled types isn't possible per se - but you could do this:
in your database layer, call the stored procedure in question; it will return a specific complex type to match its "signature"
using something like AutoMapper, you could easily copy those returned fields in the complex type into an entity of your system, thus getting a "partially filled" entity
return that entity from your database layer to the application to be used
You won't be able to avoid having lots of complex types just for the sake of getting the return values from the stored procedures - but you'll keep those locked away inside your database layer, they won't "leak out" into your entire application.
Just use System.Data.DataTable like good old days.