Connecting Entity Framework to Key Vault with Package Manager Console - entity-framework

Question

I changed my appSettings.config to no longer have connection strings as they are now all in Azure Key Vault. I was able to connect no problem, but now when I try to create the db using EF code first migrations in a new azure db using:
add-migration InitialCreate
I am getting the error:
Value cannot be null.
Parameter name: connectionString
Startup.cs
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
// Add functionality to inject IOptions<T>
services.AddOptions();
// Other configurations here such as for Blob and Notification hub
//
//
services.AddDbContext<ObContext>(opt =>
opt.UseSqlServer(Configuration["obdbqauser"]));
My Program.cs looks like this
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((context, config) =>
{
//TODO: Seperatre dev and pro - if (context.HostingEnvironment.IsProduction())
var buildConfig = config.Build();
//Create Managed Service Identity token provider
var tokenProvider = new AzureServiceTokenProvider();
//Create the Key Vault client
var keyVaultClient = new KeyVaultClient(
new KeyVaultClient.AuthenticationCallback(
tokenProvider.KeyVaultTokenCallback));
config.AddAzureKeyVault(
$"https://{buildConfig["VaultName"]}.vault.azure.net/",
keyVaultClient,
new DefaultKeyVaultSecretManager());
})

Answer 1

Here is a sample for how you can configure Key Vault as a configuration source in ASP.NET Core 2.x:
public static IWebHost BuildWebHost(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseStartup<Startup>()
.ConfigureAppConfiguration((ctx, builder) =>
{
//Build the config from sources we have
var config = builder.Build();
//Add Key Vault to configuration pipeline
builder.AddAzureKeyVault(config["KeyVault:BaseUrl"]);
})
.Build();
and a configuration would be like below:
services.AddDbContext<dbContext>(async options =>
{
var keyVaultUri = new Uri("https://xxxxxxxxx.vault.azure.net/");
var azureServiceTokenProvider = new AzureServiceTokenProvider();
var keyVaultClient = new KeyVaultClient(new KeyVaultClient.AuthenticationCallback(azureServiceTokenProvider.KeyVaultTokenCallback));
SecretBundle connectionStringSecret = await keyVaultClient.GetSecretAsync(keyVaultUri + "secrets/DBConnectionString");
options.UseSqlServer(connectionStringSecret.Value);
});
You'll need Microsoft.Extensions.Configuration.AzureKeyVault to get the configuration provider for Key Vault.
The secret naming in Key Vault will matter. For example, we will override the following connection string:
{
"ConnectionStrings": {
"DefaultConnection": "..."
}
}
You would have to create a secret named ConnectionStrings--DefaultConnection with the connection string as the value.
Then while configuring you just use Configuration["ConnectionStrings:DefaultConnection"] to get the connection string. It'll come from Key Vault if Key Vault config was added and a secret with the right name was found.
For reference , please take a look at this link.
https://entityframeworkcore.com/knowledge-base/53103236/azure-keyvault-for-dbcontext---no-database-provider-has-been-configured-for-this-dbcontext-
Hope it helps.