c# - ASP.NET Web API DELETE 方法错误

Question

使用带有 Entity Framework 的 ASP.NET Web API DELETE 方法传递学生 ID，如果该 ID 存在于表中，则删除记录。当我尝试测试它时，我收到以下错误消息

“System.Data.Entity.Utilities.Check.NotNull[T](T 值，字符串参数名称)System.Data.Entity.DbContext.Entry[TEntity](TEntity 实体)”

public class StudentController : ApiController
{
    [HttpDelete]
    [Route("student/DeleteStudent/{id}")]

    public IHttpActionResult DeleteStudent(string id)
    {
        using (var sd = new SchoolDBEntities())
        {
            var student = sd.Students
                .Where(s => s.StudentID == id)
                .FirstOrDefault();

            sd.Entry(student).State = System.Data.Entity.EntityState.Deleted;
            sd.SaveChanges();
        }
        if (id == null)
        return BadRequest("Not a valid student id");

        return Ok();
    }
}

Answer 1

您应该检查学生是否存在；

        var student = sd.Students
            .Where(s => s.StudentID == id)
            .FirstOrDefault();
        if (student != null)
        {
            sd.Entry(student).State = System.Data.Entity.EntityState.Deleted;
            sd.SaveChanges();
        }