C# XMLA TOM Connection Failing

v-sgandrathi Thank you for your reply.

I've seen those links you shared and have attemped both of the following:

string workspaceConnection = "powerbi://api.powerbi.com/v1.0/myorg/YOUR_WORKSPACE";
string tenantId = "YOUR_TENANT_ID";
string appId = "YOUR_APP_ID";
string appSecret = "YOUR_APP_SECRET";
string connectStringApp = $"DataSource={workspaceConnection};User ID=app:{appId}@{tenantId};Password={appSecret};";
server.Connect(connectStringApp);

string workspaceConnection = "powerbi://api.powerbi.com/v1.0/myorg/YOUR_WORKSPACE";
string userId = "YOUR_USER_NAME";
string password = "YOUR_USER_PASSWORD";
string connectStringUser = $"DataSource={workspaceConnection};User ID={userId};Password={password};";
server.Connect(connectStringUser);

Even when I replace myorg with my domain, I get the error: FormatException: Input string was not in a correct format.

I can connect via SSMS using myorg and not the domain name but I have the need to use code and loop through all the databases rather than manually clicking each one in SSMS.

I believe I'm creating the token correctly. I could be wrong but it is still saying invalid connection string.  I have tried multiple examples that I've found online and they all return the same. A lot of the examples use Microsoft.AnalysisServices.retail.amd64 which appears to be obsolete.

I do have a PPU license, the worksapce is set up for PPU. I'm able to authenticate and use the API to pull the report names but it doesn't give the names of the datasources.

Here's one of the examples that I've tried but still receive an invalid connection string.

using System;
using System.Threading.Tasks;
using Microsoft.Identity.Client; // Install Microsoft.Identity.Client NuGet package
using Microsoft.AnalysisServices.Tabular; // Install Microsoft.AnalysisServices.retail.amd64 NuGet package

class Program
{
    // Replace with your Azure AD app registration details
    private const string TenantId = "YOUR_TENANT_ID";
    private const string ClientId = "YOUR_CLIENT_ID";
    private const string ClientSecret = "YOUR_CLIENT_SECRET"; // For service principal auth
    private const string WorkspaceConnection = "powerbi://api.powerbi.com/v1.0/myorg/YOUR_WORKSPACE_NAME";

    // Scope for Power BI XMLA endpoint
    private static readonly string[] Scopes = { "https://analysis.windows.net/powerbi/api/.default" };

    static async Task Main()
    {
        try
        {
            // 1. Acquire token using MSAL (Service Principal)
            var app = ConfidentialClientApplicationBuilder.Create(ClientId)
                .WithClientSecret(ClientSecret)
                .WithAuthority($"https://login.microsoftonline.com/{TenantId}")
                .Build();

            var result = await app.AcquireTokenForClient(Scopes).ExecuteAsync();
            string accessToken = result.AccessToken;

            Console.WriteLine("✅ Token acquired successfully.");

            // 2. Connect to Power BI workspace via TOM using token
            using (var server = new Server())
            {
                // Pass token in connection string
                string connectionString = $"DataSource={WorkspaceConnection};Password={accessToken};";
                server.Connect(connectionString);

                Console.WriteLine("✅ Connected to workspace via TOM.");

                // Example: List all datasets (models) in the workspace
                foreach (var db in server.Databases)
                {
                    Console.WriteLine($"Dataset: {db.Name} (ID: {db.ID})");
                }

                server.Disconnect();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"❌ Error: {ex.Message}");
        }
    }
}

v-sgandrathi Thank you for your reply.  I read somewhere today that Premium Per User workspaces cannot use a service principal.  So, I tried to do it with an interactive token but I still get the same invalid connection string error.

When I go to the Application API permissions, I only see two entries.

So, this led me down to make sure I have other items set up correctly and screenshots are below:
XMLA Endpoint:

Service Principal permissions - all set with a security group that the service principal is a member of:

Am I missing something else?