C#

DataTable sheet1 = new DataTable("Excel Sheet");
               OleDbConnectionStringBuilder csbuilder = new OleDbConnectionStringBuilder();
               csbuilder.Provider = "Microsoft.ACE.OLEDB.12.0";
               csbuilder.DataSource = filename;
               csbuilder.Add("Extended Properties", "Excel 12.0 Xml;HDR=YES");
               string selectSql = @"SELECT * FROM [Sheet1$]";



               using (OleDbConnection connection = new OleDbConnection(csbuilder.ConnectionString))


               using (OleDbDataAdapter adapter = new OleDbDataAdapter(selectSql, connection))
               {

                   connection.Open();
                   adapter.Fill(sheet1);

                   connection.Close();


               }

using Microsoft.EntityFrameworkCore;

namespace EFCoreDBFirstExample.Models
{
    public partial class ModelContext : DbContext
    {
        public virtual DbSet Departments { get; set; }
        public virtual DbSet Employees { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            var connectionString = @"Server=MAROIS_KEVIN_1\SQLEXPRESS;Database=Test;Trusted_Connection=true;Encrypt=false;";
            optionsBuilder.UseSqlServer(connectionString, options => options.EnableRetryOnFailure());
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity(entity =>
            {
                entity.ToTable("Departments", "public");

                entity.HasKey(e => e.DepartmentId)
                      .HasName("DeptartmentId");

                entity.Property(e => e.DepartmentId)
                      .HasColumnName("DeptartmentId");

                entity.Property(e => e.DepartmentName)
                    .HasColumnName("DepartmentName")
                    .HasColumnType("varchar")
                    .HasMaxLength(30);
            });

            modelBuilder.Entity(entity =>
            {
                entity.ToTable("EmployeeName", "public");

                entity.HasKey(e => e.EmployeeId)
                      .HasName("EmployeeId");

                entity.Property(e => e.EmployeeId)
                      .HasColumnName("EmployeeId");

                entity.Property(e => e.EmployeeName)
                    .HasColumnName("EmployeeName")
                    .HasColumnType("varchar")
                    .HasMaxLength(30);
            });
        }
    }
}

using EFCoreDBFirstExample.Models;

using (var db = new ModelContext())
{
    // Creating a new department and save it to the database
    var newDept = new Departments();
    newDept.DepartmentId = 1;
    newDept.DepartmentName = "Development";

    db.Departments.Add(newDept);
    var count = db.SaveChanges(); //<======================= ERROR HERE

    Console.WriteLine("{0} records saved to database", count);

    // Retrieve and display the data
    Console.WriteLine();
    Console.WriteLine("Departments:");
    foreach (var dept in db.Departments)
    {
        Console.WriteLine($"{dept.DepartmentId}: {dept.DepartmentName}" );
    }

    Console.ReadLine();
}

Microsoft.EntityFrameworkCore.Storage.RetryLimitExceededException
  HResult=0x80131500
  Message=The maximum number of retries (6) was exceeded while executing database operations with 'SqlServerRetryingExecutionStrategy'. See the inner exception for the most recent failure.

Inner Exception 1:
SqlException: Cannot open database "Test" requested by the login. The login failed.
Login failed for user 'MAROIS_KEVIN_1\kevin'.