Hi Thomas!

I'm not sure if this is what you are looking for? 

The key is on the Service* (Take a look the If case)

Steps:

1.- Created the DataContexts (2) (Assuming the two tables on the two databases are identical structure)

Refer: Add a Database Context

2.- Create the Model

/////////////// CustomersModel.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using SnapObjects.Data;
using DWNet.Data;

namespace restapi.Models
{
    [DataWindow("d_customers", DwStyle.Grid)]
    [Table("customer")]
    #region DwSelectAttribute  
    [DwSelect("PBSELECT( VERSION(400) TABLE(NAME=\"customer\" ) @(_COLUMNS_PLACEHOLDER_) )")]
    #endregion
    [DwKeyModificationStrategy(UpdateSqlStrategy.DeleteThenInsert)]
    [UpdateWhereStrategy(UpdateWhereStrategy.KeyAndConcurrencyCheckColumns)]
    public class CustomersModel
    {
        [Key]
        [DwColumn("customer", "id")]
        public int Id { get; set; }

        [ConcurrencyCheck]
        [StringLength(15)]
        [DwColumn("customer", "fname")]
        public string Fname { get; set; }

        [ConcurrencyCheck]
        [StringLength(20)]
        [DwColumn("customer", "lname")]
        public string Lname { get; set; }

        [ConcurrencyCheck]
        [StringLength(20)]
        [DwColumn("customer", "city")]
        public string City { get; set; }

        [ConcurrencyCheck]
        [StringLength(35)]
        [DwColumn("customer", "company_name")]
        public string Company_Name { get; set; }

    }

}

3.- Scaffolding (Service and Controller from Model SqlModelMapper)

4.- Change code on the Service and on the Interface

///////////Service*

public class CustomersService : ICustomersService
{
private readonly AppeonSampleDataContext _dataContext;
private readonly AppeonSampleADataContext _dataContextA;

public CustomersService(AppeonSampleDataContext dataContext, AppeonSampleADataContext adataContext)
{
_dataContext = dataContext;
_dataContextA = adataContext;
}

public IList<CustomersModel> Retrieve(int clientID)
{
if(clientID == 0)
return _dat aContextA.SqlModelMapper.Load<CustomersModel>().ToList();
else
return _dataContext.SqlModelMapper.Load<CustomersModel>().ToList();
}

/////////////////////Interfase

public interface ICustomersService
{

IList<CustomersModel> Retrieve(int clientID);

}

///////////////// Controller

// In the controller added {clientId} on the HttpGet Method

// URL: "http://localhost:5000/api/Customers/Retrieve/1"

 //GET api/Customers/Retrieve/clientId
[HttpGet("{clientId}")]
[ProducesResponseType(typeof(IList<CustomersModel>), StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status500InternalServerError)]
public ActionResult<IList<CustomersModel>> Retrieve(int clientId)
{
try {
var result = _icustomersservice.Retrieve(clientId);
Return Ok(result);
}
catch (Exception ex)
{
return StatusCode(StatusCodes.Status500InternalServerError, ex.Message);
}
}

6. My final startup.cs 

///////////////////////////////// Startup.cs 

// Startup.cs with the 2 DataContexts added

public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(m =>
            {
                m.UseCoreIntegrated();
                m.UsePowerBuilderIntegrated();
            })
            .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddDataContext<AppeonSampleADataContext>(m => m.UseSqlServer(this.Configuration,              "AppeonSample"));
            services.AddDataContext<AppeonSampleDataContext>(m => m.UseSqlServer(this.Configuration, "AppeonSample"));
            services.AddScoped<ICustomersService, CustomersService>();

            services.AddGzipCompression(CompressionLevel.Fastest);

7. Create a client on PowerBuilder

////////////////Client ///////////////////

// Power Builder as Rest Client /

RestClient lrc_Client
String ls_Url, ls_Method
Long ll_rtn

//test 1: 

ls_Url = "http://localhost:5000/api/Customers/Retrieve/1"

//test 2: 

// ls_Url = "http://localhost:5000/api/Customers/Retrieve/0"

dw_customers.clear( )

lrc_Client = Create RestClient
ls_Method = "GET"
lrc_Client.SetRequestHeader ("Content-Type", "application/json")
lrc_Client.SetRequestHeader("Accept-Encoding", "gzip")

ll_rtn = lrc_Client.Retrieve( dw_customers,ls_Url )
If ll_rtn >= 0 And lrc_Client.GetResponseStatusCode() = 200 Then
MessageBox( "Retrieve Success","Rows:" + String ( ll_rtn ))
Else
MessageBox(
"Retrieve Failed","Rows:" + String ( ll_rtn ))
End If

If IsValid (lrc_Client) Then Destroy ( lrc_Client )

////////////////////////////////////////////////////

Hope it works for you! 

Armando, 

Attached is zip file containing the files you asked for along with other related classes.  I was thinking of sending a client ID in the request header and storing that using middleware (see startup.cs and logging.cs).  Then using the OnConfiguring method to switch between databases/connection strings.  I've been unable to get the commented code in SampleDataContext.cs to work however.  The UploadImportFile is a method in SampleController.cs that would need to switch databases depending on which client app called it.  Any examples/suggestions you could provide would be great.

Thanks, Tom

Hi Thomas, 

Is it possible to share with us your appsettings.json file and your database context class?. Just to be able to see what you are doing but I don't see too much of a problem in putting one more variable to the URL and making a switch case in the controller and use as many datacontext as databases you want to connect.

Regards!