设置Statement返回Null

Question

我在获取要提交给数据库的属性值时遇到问题。我的get语句中有逻辑，它根据来自其他两个属性的值返回一个值。逻辑正常工作并在“我的网页”中显示正确的值，但是“评级字段”的值始终在数据库中设置为“空”。我的代码如下 - 如果有人能指出我正确的方向，那将非常感激。

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace PSA.Models
{
    public class Issue
    {
        public virtual int IssueID { get; set; }
        public virtual int ProbableClassificationId { get; set; }
        public virtual ProbableClassification ProbableClassification { get; set; }
        public virtual int SeverityClassificationId { get; set; }
        public virtual SeverityClassification SeverityClassification { get; set; }
        string ratingstatus;
        public virtual string Rating 
        {
            get 
            {
                if (ProbableClassification != null && SeverityClassification != null)
                {
                    if (SeverityClassification.Severity == "Minor")
                    {
                        ratingstatus = "Low";
                    }
                    if (ProbableClassification.Probability == "Not Likely" && SeverityClassification.Severity == "Medium")
                    {
                        ratingstatus = "Low";
                    }
                    if (ProbableClassification.Probability == "Likely" && SeverityClassification.Severity == "Medium")
                    {
                        ratingstatus = "Medium";
                    }
                    if (ProbableClassification.Probability == "Definitely" && SeverityClassification.Severity == "Medium")
                    {
                        ratingstatus = "Medium";
                    }
                    if (ProbableClassification.Probability == "Not Likely" && SeverityClassification.Severity == "Major")
                    {
                        ratingstatus = "Low";
                    }
                    if (ProbableClassification.Probability == "Likely" && SeverityClassification.Severity == "Major")
                    {
                        ratingstatus = "High";
                    }
                    if (ProbableClassification.Probability == "Definitely" && SeverityClassification.Severity == "Major")
                    {
                        ratingstatus = "Crtical";
                    }

                }
            return ratingstatus;
            }
            set
            {
                ratingstatus = value;
            }
        }

    }
}