如何在单个 API 方法中使用 EF Core 更新多个表

Question

I have 2 tables and 2 models for each table, Employee and EmployeeHistory . I have one API method in which I am checking if the employee details found, then insert old data from the Employee table into the EmployeeHistory table and then update the data in Employee table with payload from API.

I have below code written for it. I am stuck at updating the EmployeeHistory table. I can update the Employee table with payload, but I'm not sure how to write code to update the EmployeeHisory table. Can you please help? Thanks in advance.

    public class Employee
    {
      
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int EmpId { get; set; }
        public int EmpName { get; set; }
        public int Address{ get; set; }
        public int MobNumber{ get; set; }
        public EmployeeHistory EmployeeHistory { get; set; }
    }

 
    public class EmployeeHistory
    {
      
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }
        public int EmpId { get; set; }
        public int OldAddress{ get; set; }
        public int OldMobNumber{ get; set; }
        public Employee Employee{ get; set; }

    }`


        [HttpPut]
        public async Task<ActionResult> UpdateEmpDetails([FromBody] EmployeeDto employeeDto)
        {       
        var emp = await _repository.GetEmployee(employeeDto.EmpId, employeeDto.EmpName);
                //if member details found, update the record
                if(emp != null)
                {
                    //create new entry in EmployeeHistory table
                    var history = new EmployeeHistory();
                    history.OldAddress = emp.Address;
                    history.OldMobNumber = emp.MobNumber;

                    emp.EmployeeHistory = history;

                    //update record in Employee table
                    emp.Address = employeeDto.MemberId;
                    emp.MobNumber = employeeDto.FlagRefName;

                    await _dbcontext.SaveChanges();

                    return Ok();
                }
}

I am getting an error at SaveChanges() function as 

> An error occurred while saving the entity changes. See the inner exception for details. String or binary data would be truncated.

Answer 1

If Employee and EmployeeHistory are different you'll need to write a mapper to convert the DTO from an Employee to Employee history then insert that object to your EmployeeHistory table.

Something along the lines of

var history = new EmployeeHistory()
    {
      //Mapping logic between the DTOs
      Property = employee.Property
      ...... 
    };
_context.EmployeeHistory.Add(history);
_context.SaveChanges();