[WebToolsE2E][Aspire] After adding Aspire.Microsoft.EntityFrameworkCore.Cosmos, add related code to the program.cs shows error: There is no argument given that corresponds to the required parameter 'databaseName' ...

[v-cazhang]

INSTALL STEPS

1. Clean machine: Win11 x64 23h2 ENU
2. Install VS 17.9 P1

REPRO STEPS

1. In the VS, create a new project > ASP.NET Core Web App (Model-View-Controller) > .NET 8.0 > none > check 'Enlist in Aspire Orchestration' > Create.
2. Right-click the Models folder and add a new class file named Movie.cs, paste following codes:

public class Movie
	{
	    public int ID { get; set; }
	    public string Title { get; set; } = string.Empty;
	    public DateTime ReleaseDate { get; set; }
	    public string Genre { get; set; } = string.Empty;
	    public decimal Price { get; set; }
	}

3. Right-click the Controllers folder > Add > Controller > MVC Controller with views, using Entity Framework

   • Model class: Movies.cs
   • DbContext class: click '+' to create a new db context
   • Database provider: select Azure Cosmos DB

4. Right-click web project > Add > Aspire component > Aspire.Microsoft.EntityFrameworkCore.Cosmos > install

5. Open appsettings.json file of web project, add following codes:

"Aspire": {
	    "Microsoft": {
	      "EntityFrameworkCore": {
	        "Cosmos": {
	          "DbContextPooling": true,
	          "Tracing": false
	        }
	      }
	    }
	  }

7. Open Program.cs file of web project, add following code:
   builder.AddCosmosDbContext<MyDbContext>("myConnection");

ACTUAL
Shows error under 'AddCosmosDbContext;':
There is no argument given that corresponds to the required parameter 'databaseName' of 'AspireAzureEFCoreCosmosDBExtensions.AddCosmosDbContext(IHostApplicationBuilder, string, string, Action?, Action?)'

Notes:

1. According to the error message, change 'builder.AddCosmosDbContext("myConnection");' to 'builder.AddCosmosDbContext("myConnection"; "myConnection");', the error will disappear.
   

EXPECTED
No error shows

[Pilchie]

How do you expect Entity Framework to know what database name to use if you don't specify one?

[eerhardt]

@Pilchie - looks like we need to update the README for CosmosDB EF:

aspire/src/Components/Aspire.Microsoft.EntityFrameworkCore.Cosmos/README.md

Lines 19 to 25 in b6fd5fd

	## Usage example
	In the _Program.cs_ file of your project, call the `AddCosmosDbContext` extension method to register a `DbContext` for use via the dependency injection container. The method takes a connection name parameter.
	```csharp
	builder.AddCosmosDbContext<MyDbContext>("cosmosdb");
	```

Just following this README doesn't work.