c# - 列表不是附加的，而是它的覆盖

Question

谁能告诉我为什么当我单击新按钮时，我的列表中的 getapprias 被第 184 行删除了。下面的粘贴箱链接将新记录添加到顶部声明的列表中。

// 私有列表 apprList; 绑定列表apprList；

http://pastebin.com/f1SJxtay

我在屏幕上的绑定源如下：

BindingSource bs = new BindingSource();
bs.DataSource =  pamsContext.GetAppraisals(empNo);
grvappraisal.DataSource = bs;

以下粘贴箱显示了这一点：

public List<AppraisalList> GetAppraisals(int empno)
{
    List<AppraisalList> appraisal = new List<AppraisalList>();

    try
    {
        var q = from appr in pamsEntities.appraisals
                where (appr.emp_no == empno)
                select new
                {
                    Contract_id=appr.contract_id,
                    EmployeeId=appr.emp_no,
                    Career_Id =appr.career_id,
                    Appraisal_Date=appr.appraisal_date,
                    appraised_by = appr.appraised_by,
                    Next_Date=appr.next_date,
                    Rating=appr.rating,
                    notes = appr.notes,
                    Submitted = appr.submitted,
                    Readiness = appr.Readiness,
                    Talentrating = appr.TalentRating,
                    Performancescore = appr.PerformanceScore
                };

        if (q != null)
        {
            Array.ForEach(q.ToArray(), appr =>
            {

                appraisal.Add(new AppraisalList(
                    appr.EmployeeId, 
                    0, 
                    appr.Contract_id, 
                    Convert.ToDateTime("15/08/2013"),
                    appr.appraised_by, 
                    Convert.ToDateTime("15/08/2013"), 
                    90, 
                    "test", 
                    Convert.ToDateTime("15/08/2013"), 
                    1, 
                    2, 
                    3));
            });
        }
        return appraisal;
    }

    catch (Exception ex)
    {
        throw new EntityContextException("GetAppraisals failed.", ex);
    }

}