Azure Functions, Entity Framework and Oracle DB - basic POC fails - visual-studio

Question

I'm having a lot of trouble getting a basic proof-of-concept working, in which I am accessing an Oracle DB (11g) through Azure Functions via Entity Framework (6.2).
Prerequisites:
ODT For Visual Studio 2017 is installed, as well as Azure Functions CLI/Core Tools. Everything mentioned below is done entirely via Visual Studio 2017, not through Azure portal.
Take 1:
Created a new project with the Azure Functions template.
Installed NuGet packages EntityFramework (6.2.0), Oracle.ManagedDataAccess (12.2.1100) and Oracle.ManagedDataAccess.EntityFramework (12.2.1100). Note: When installing NuGet packages in projects using the Azure Functions template, the packages are added under Dependencies -> NuGet, rather than under References.
Added ADO.NET Entity Data Model to project.
Problem: After setting my connection string, choosing Entity Framework 6.x is unavailable, with the following error message:
An Entity Framework database provider compatible with the latest
version of Entity Framework could not be found for your data
connection. If you have already installed a compatible provider,
ensure you have rebuilt your project before performing this action.
Otherwise, exit this wizard, install a comaptible provider, and
rebuild your project befre performing this action.
As the simplest of workarounds, I have tried to just go ahead with EF5, but it throws an exception while creating the DB model (after selecting the objects to include in model, including some stored procedures).
Take 2:
Created project and installed NuGet packages as above.
Created class library project to facilitate the Oracle interactions.
Installed the same NuGet packages as above in the class library project.
Added ADO.NET Entity Data Model to class library project and added some database objects to the database model. Also added custom constructor to the model for specific connection string, because managing connection strings in Azure Functions was a seperate set of headaches that I'll deal with later.
Added a simple wrapper method to the class library project that calls a stored procedure from the database model:
public static string NameByEmpNo(int empNo)
{
string result;
MyEntities entities = new MyEntities("metadata=res://*/MyEntities.csdl|res://*/MyEntities.ssdl|res://*/MyEntities.msl;provider=Oracle.ManagedDataAccess.Client;provider connection string='DATA SOURCE=127.0.0.1:1521/ORCL;PASSWORD=tiger;USER ID=SCOTT'");
ObjectParameter name = new ObjectParameter("o_empname", typeof(string));
entities.GET_EMP_NAME_PROC(empNo, name);
result = (string)name.Value;
return result;
}
Added reference to the class library in the Azure Functions project.
Added function that calls NameByEmpNo:
[FunctionName("GetNameByEmpNo")]
public static async Task<HttpResponseMessage> GetNameByEmpNo([HttpTrigger(AuthorizationLevel.Function, "get", Route = null)]HttpRequestMessage req, TraceWriter log)
{
int empNo = Int32.Parse(req.GetQueryNameValuePairs()
.FirstOrDefault(q => string.Compare(q.Key, "empno", true) == 0)
.Value);
string empName = ScottAccess.NameByEmpNo(empNo);
return req.CreateResponse(HttpStatusCode.OK, "Employee name: " + empName);
}
Problem: At runtime, calling the function fails with this error
message:
Exception while executing function: GetNameByEmpNo -> The ADO.NET
provider with invariant name 'Oracle.ManagedDataAccess.Client' is
either not registered in the machine or application config file, or
could not be loaded. See the inner exception for details. -> Unable to
find the requested .Net Framework Data Provider. It may not be
installed.
Bonus info: My class library works perfectly when called through a console application. Also, my Azure Functions app works perfectly when calling functions that do not use my class library...
I am stumped. Has anyone got experience with getting this combination of techs working together and can offer some insight into where I'm going wrong / provide steps to get a basic connection working?

Answer 1

Entity Framework within Azure Functions defaults the providers to System.Data.SqlClient so SQL connections will work without any configuration changes, but that means you have to do something special for Oracle connections. The problem seems to come from the config values that the Oracle.ManagedDataAccess.Client library assumes are available within the App.Config or Web.Config file in the project, which are inserted whenever you install the Oracle.ManagedDataAcess.EntityFramework Nuget package. Azure Functions don't have config files, and I wasn't able to find any way to specify the Oracle provider in the settings json files.
I found a solution in this post
It suggests bypassing this mechanism and creating a DbConfiguration for Oracle, then using DbConfigurationType to tell the DbContext which configuration you're using.
public class OracleDbConfiguration : DbConfiguration
{
public OracleDbConfiguration()
{
SetDefaultConnectionFactory(new OracleConnectionFactory());
SetProviderServices("Oracle.ManagedDataAccess.Client", EFOracleProviderServices.Instance);
SetProviderFactory("Oracle.ManagedDataAccess.Client", new OracleClientFactory());
}
}
[DbConfigurationType(typeof(OracleDbConfiguration))]
public partial class MyEntities : IGISContext
{
//Expose Connection String Constructor
public MyEntities(string connectionString, int commandTimeoutInSeconds = 30) : base(connectionString)
{
this.Database.CommandTimeout = commandTimeoutInSeconds;
}
}
Note: I used EF 6 Database First to generate my EDMX; MyEntities here is a partial class for providing a constructor that takes in a connection string.
The oracle connection wil use the specified DbConfiguration class, and any SQL database connections will continue to work using the defaults.
My solution is using the Nuget Packages:
EntityFramework 6.2.0
Oracle.ManagedDataAccess 12.2.1100
Oracle.ManagedDataAccess.EntityFramework 12.2.1100