从C＃实体框架MVC创建表的异常

Question

public class SalesERPDAL:DbContext
{
    public DbSet<Employee> Employees;
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Employee>().ToTable("TblEmployee");
        base.OnModelCreating(modelBuilder);
    }
}

public class EmployeeBusinessLayer
{
    public List<Employee> GetEmployees()
    {
        SalesERPDAL salesDalObj = new SalesERPDAL();
        return salesDalObj.Employees.ToList(); **//Getting error on this call**
    }
}


public class Employee
{
    [Key]
    public int EmployeeId { get; set; }
    public string FName { get; set; }
    public string LName { get; set; }
    public int Salary { get; set; }
}

webconfig connection string:

<connectionStrings>
<add name="SalesERPDAL" connectionString="Data Source=CSCINDAI406933\\SQLEXPRESS;Initial Catalog=SalesERPDB;Integrated Security=True;"></add>

Trying to create a table "TblEmployee" from "SalesERPDAL" class, as mentioned above. But I'm getting a runtime error on calling "salesDalObj.Employees.ToList();" from GetEmployees() from EmployeeBusinessLayer class.

Exception details: Argument Null exception was unhandled by user code: An exception of type 'System.ArgumentNullException' occurred in System.Core.dll but was not handled in user code Additional information: Value cannot be null.

I'm able to connect to this DataBase from a different application. I'm new to Entity framework, not sure why the application is breaking. Help would really be appreciated. Thanks in advance.

Answer 1

You need to pass connection string name to DbContext

public class SalesERPDAL: DbContext
{
   public SalesERPDAL() : base("connectionStringName") { }
  public DbSet<Employee> Employees { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Employee>().ToTable("TblEmployee");
        base.OnModelCreating(modelBuilder);
    }
}