'Value cannot be null. (Parameter 'connectionString')' - Azure Function - Entity Framework Core

Question

This is in my startup file (Dependency Injection)

public override void Configure(IFunctionsHostBuilder builder)
    {
       

        builder.Services.AddDbContext<CatsDBContext>(
            options =>
            {
                const string Name = "SqlConnectionString";
                options.UseSqlServer(Configuration.GetConnectionString(Name));
            });

This is my local.settings.json

{
    "IsEncrypted": false,   "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet"   },
     "ConnectionStrings": {
    "SqlConnectionString": "Server=tcp:animal77.database.windows.net,1433;Initial Catalog=CatsDB;Persist Security Info=False;User ID=j;Password=A;MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;"
       } }

This is my context

namespace Shizzle.Models
{
    public partial class CatsDBContext : DbContext
    {
        public CatsDBContext()
        {
        }

        public CatsDBContext(DbContextOptions<CatsDBContext> options)
            : base(options)
        {
            
        }

        public virtual DbSet<Cats> Cats { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
#warning 
          //  optionsBuilder.UseSqlServer("Server=tcp:animal77.database.windows.net,1433;Initial Catalog=CatsDB;Persist Security Info=False;User ID=j;Password='';MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;");
            }

This is my function that I want it to do to the db

namespace Shizzle
{
    public  class Function1
    {
        private readonly CatsDBContext _applicationDbContext;

        public Function1(CatsDBContext applicationDbContext)
        {
            _applicationDbContext = applicationDbContext;
        }

        [FunctionName("Function1")]
        public async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");
            
            string name = req.Query["name"];

            var demo = new Cats { Name = "Jason", Id = 5 };
            _applicationDbContext.Cats.Add(demo);
            _applicationDbContext.SaveChanges();

and this is my startup DI class :

[assembly: FunctionsStartup(typeof(Startup))]

namespace Shizzle
{
    class Startup : FunctionsStartup
     {

       public IConfiguration Configuration { get;  }

        public override void Configure(IFunctionsHostBuilder builder)
        {
           

            builder.Services.AddDbContext<CatsDBContext>(
                options =>
                {
                    const string Name = "SqlConnectionString";
                    options.UseSqlServer(Configuration.GetConnectionString(Name));
                });
            

        }

        }
   
}

And I am getting this error in Visual Studio 2019

What can I try next?

For one thing, the connection strings object should be within "values" object. Not sure if the object works in there though, you could also instead use a top-level setting within the values object. — juunas
– juunas, Commented Aug 26, 2021 at 11:41
if I add it in their the intelisense does not bring up ConnectionStrings, whereas where I put it, it does. — Jason_Hough
– Jason_Hough, Commented Aug 26, 2021 at 11:44
Where is the logic where you build your configuration? Where does your Configuration object come from? — Joost K
– Joost K, Commented Aug 26, 2021 at 11:58

Joost K · Accepted Answer · 2021-08-26 12:07:48Z

1

You're missing the logic to build your configuration

the best way in my opinion is to also override ConfigureAppConfiguration

public override void ConfigureAppConfiguration(IFunctionsConfigurationBuilder builder) 
{
  Configuration = builder.ConfigurationBuilder.Build();
}

But you might also be able to add this in your Configure function

answered Aug 26, 2021 at 12:07

Joost K

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1 Comment

Jason_Hough Over a year ago

Top Man ! Thanks you

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