Tighten up nullability

Author: stuartpa

MssqlMcp/MssqlMcp/SqlConnectionFactory.cs

@@ -8,9 +8,20 @@ public class SqlConnectionFactory : ISqlConnectionFactory
 {
     public async Task<SqlConnection> GetOpenConnectionAsync()
     {
-        var connectionString = SqlConnectionManager.GetSqlConfig();
+        var connectionString = GetConnectionString();
+
+        // Let ADO.Net handle connection pooling
         var conn = new SqlConnection(connectionString);
         await conn.OpenAsync();
         return conn;
     }
+
+    private static string GetConnectionString()
+    {
+        var connectionString = Environment.GetEnvironmentVariable("CONNECTION_STRING");
+
+        return string.IsNullOrEmpty(connectionString)
+            ? throw new InvalidOperationException("Connection string is not set in the environment variable 'CONNECTION_STRING'.\n\nHINT: Have a local SQL Server, with a database called 'test', from console, run `SET CONNECTION_STRING=Server=.;Database=test;Trusted_Connection=True;TrustServerCertificate=True` and the load the .sln file")
+            : connectionString;
+    }
 }